Ch.3 - Chemical ReactionsWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Mass Percent is the percentage of a particular element within a compound. 

Atomic Mass Vs. Molecular Mass

Concept #1: Understanding the difference between Atomic Mass & Molecular Mass

In order to find the atomic mass of an element you must look it up on your periodic table. 

The total mass of a compound is the sum of each elemental atomic mass. 

Example #1: What is the total mass of each of the following compounds?

a. N2O5                                                            b. C12H22O11                                        c.  (NH4)3PO4

Examining Mass Percent

Concept #2: Understanding Mass Percent

Example #2: What is the percentage of carbon in sodium hydrogen carbonate, NaHCO3?

In order to calculate the molecular mass or weight of a compound you must look up the atomic mass or weight of each element. 

Example #3: A sample of toothpaste contains tin (II), SnF2. Analysis of a 5.25 g sample contains 8.77 x 10-3 g of F. What is the percentage of tin (II) fluoride in the sample? 

To go from the atomic mass of an element to the molecular mass of a compound you must use stoichiometric relationships. 

Practice: Hemoglobin contains 0.33% iron and has a molecular weight of 68 kg. How many iron atoms are in each molecule of hemoglobin?

Additional Problems
What is the weight percent, with respect to RbCl, of a solution if you mix 20.452 g of RbCl in 275.00 mL of water 31oC? The density of water is 0.9954 g/cm3 at 31oC.  A. 6.95% B. 7.47% C. 6.89% D. 7.40% E. 7.44%
What is the mass percent of hydrogen in LiNH 2? A. 4.39% B. 50.0% C. 11.4% D. 8.78%
What percent of the mass of the compound, K2PbO3, is due to lead? A. 83.1% B. 88.8% C. 95.0% D. 62.1% E. 56.9%
Calculate the mass percent composition of sulfur in Al 2(SO4)3. A) 28.12 % B) 9.372 % C) 42.73 % D) 21.38 % E) 35.97 %
What mass of NaCl is contained in 24.88 g of a 15.00% by mass solution of NaCl in water? A) 20.00 g B) 21.15 g C) 3.73 g D) 1.50 g E) 12.44 g
A solution is prepared by dissolving 98.6 g of NaCl in enough water to form 875 mL of solution. Calculate the mass % of the solute if the density of the solution is 1.06 g/mL. A) 11.3% B) 12.7% C) 9.4% D) 10.6% E) 11.9%
A crystalline sample that has the formula MgCl 2.6H2O loses a portion of its water when it is dried in an oven for several hours but undergoes no other changes. If the student, Dora the Explorer, started with 10.000 g of the compound and ended up with a residue that weighed 7.342 g., what is the formula of the residue?   a) MgCl2.H2O b) MgCl2.2H2O c) MgCl2.3H2O d) MgCl2.4H2O e) MgCl2.5H2O
A sample is composed of a mixture of NaBr and CuSO4.5H2O. A chemist decided to analyze the mixture by dehydrating it by heating it to 120°C for 12 hours which removed all of the water present. If a 6.523 sample weighed 4.967 g after dehydration, what is the percentage of NaBr in the original hydrated sample?   a) 22.4 b) 33.9 c) 39.2 d) 79.7 e) none of the answers is within 5% of the correct answer.
Manganese comprises 1.3 x 10 -1 percent by mass of the elements found in a normal healthy body. How many grams of manganese would be found in the body of a person weighing 183 lb? A. 87.6 g B. 45.6 g C. 879 g D. 112 g E. 108 g
The compound dibromobis (ethylenediamine) cobalt(III) chloride has a formula of [Co(C2N2H8)2Br2]Cl. What is the mass percent hydrogen in the compound? a. 0.27% b. 4.32% c. 2.16% d. 8.63% e. 0.54%
Calculate the mass percent composition of sulfur in Al 2(SO4)3. The molar mass of Al2(SO4)3 is 342.17 g/mol. A) 9.372%             B) 21.38%       C) 28.12%       D) 35.97%       E) 42.73%
Calculate the mass percent composition of sulfur in Al  2(SO4)3.
What is the percentage by mass of N in Cu(NO 3)2?   a) 4.38 b) 8.75 c) 14.9 d) 33.9 e) 70.0
Malachite is a green colored mineral that is 57.5% copper.  What mass of copper is present in a 250.0 g sample of malachite?                A)  63.6 g             B)  127 g              C)  435 g              D)  36.5 g             E)  144 g
The main source of copper on earth is a mineral called chalcocite, which is copper(I) sulfide. a)  What is the formula of this compound?  _________ b)  What is the mass percent of copper in this compound?
Clonidine, C9H9Cl2N3 is a antihypertensive drug often used to treat attention-deficit hyperactivity disorder. What is the percent composition of nitrogen in Clonidine? A. 6.09% B. 46.97% C. 13.04% D. 30.81% E. 18.27% 
The complete combustion of 0.285 g of a pure hydrocarbon yielded 0.878 g CO 2 and 0.405 g H2O. What is the mass % C in this hydrocarbon? A) 24.0% B) 72.7% C) 27.3% D) 32.4% E) 84.1%
A 1.28 g sample of copper is heated with sulfur to produce 1.6 g copper sulfide. Calculate the mass percentages of copper and sulfur in the compound.
The molecular formula for a sugar molecule is C12H22O11. What is the percent of carbon in the molecule? A) 42.12% B) 2.37% C) 26.67% D) 67.88% E) 8.34%
Suppose you are working for a pharmaceutical company, and your boss has tasked you with identifying the contents of a bottle containing an unknown white crystalline compound. You have narrowed down the possibilities to sodium carbonate (Na2CO3) and sodium oxalate (Na2C2O4). Sodium carbonate is relatively harmless (a common ingredient in commercial water softeners), but sodium oxalate is extremely toxic to humans; it is therefore very important that you properly identify the unknown compound. You perform an experiment, and your results show the compound is about 43% sodium by mass. Use this information to identify your compound.
What is the percent mass of H2O in Epsom salt, CaSO4·7H2O?
Calculate the percentage by mass of lead in Pb(NO3)2.  a. 38.6% b. 44.5% c. 62.6% d. 65.3% e. 71.2%
Calculate the mass percent composition of lithium in Li 3PO4. A) 20.82 % B) 30.72 % C) 55.27 % D) 17.98 % E) 26.75 %
What is the % of carbon by mass in Calcium Cyanide Ca(CN) 2? A. 13.039 % B. 17.541 % C. 26.078 % D. 30.412 % E. None of these choices are correct.
Calculate the mass percent composition of lithium in Li3PO4. A) 26.75 % B) 17.98 % C) 30.72 % D) 55.27 % E) 20.82 %
What is the percent by mass of oxygen in Ca(NO3)2? a) 29.3% b) 47.1% c) 58.5% d) 94.1%
Which of these compounds contains the greatest percentage of nitrogen? a) C6H3N3O7 b) CH4N2O c) LiNH2 d) Pb(N3)2
Phenylenediamine (pictured below) is mainly used as a component of engineering polymers and composites. It is also an ingredient in hair dyes and is occasionally used as a substitute for henna. What is the percent mass of carbon in phenylenediamine? a. 66.6% b. 11.1% c. 7.45% d. 25.9%
Calculate the mass percent of iodine in strontium iodate a. 58% b. 29% c. 41% d. 48% e. 67%
Copper (II) fluoride contains 37.42% F by mass.Use this percentage to calculate the mass of fluorine (in g) contained in 55.5 g of copper (II) fluoride.
Common brass is a copper and zinc alloy containing 37.0% zinc by mass and having a density of 8.48 g/cm3. A fitting composed of common brass has a total volume of 120.5 cm3 .How many atoms of zinc does the fitting contain?
A 67.2 g sample of a gold and palladium alloy contains 3.20×1023 atoms .What is the mass percentage of the gold in the alloy?
A 67.2 g sample of a gold and palladium alloy contains 3.20×1023 atoms .What is the mass percentage of the palladium in the alloy?
A phosphorus compound that contains 34.00% phosphorus by mass has the formula X3P2.Identify the element X.
A particular brand of beef jerky contains 5.51×10−2% sodium nitrite by mass and is sold in an 8.00-oz bag.What mass of sodium does the sodium nitrite contribute to sodium content of the bag of beef jerky?
Phosphorus is obtained primarily from ores containing calcium phosphate.If a particular ore contains 57.1 % calcium phosphate, what minimum mass of the ore must be processed to obtain 1.00 kg of phosphorus?
Because of increasing evidence of damage to the ozone layer, chlorofluorocarbon (CFC) production was banned in 1996. However, many older cars still have air conditioners that use CFC-12 (CF2C2). These air conditioners are recharged from stockpiled supplies of CFC-12. Suppose that 100 million automobiles each contain 1.2 kg of CFC-12 and leak 26 % of their CFC-12 into the atmosphere per year.How much chlorine, in kg, is added to the atmosphere each year due to these air conditioners?
One of the best-selling light, or low-calorie, beers is 4.4 % alcohol by volume and a 12-oz serving contains 110 Calories; remember: 1 Calorie = 1000 cal = 1 kcal. To estimate the percentage of Calories that comes from the alcohol, consider the following questions. If 4.4 % of the total volume is ethanol and the density of ethanol is 0.789 g/mL, what mass of ethanol does a 12-oz serving of light beer contain?
Pure gold is usually too soft for jewelry, so it is often alloyed with other metals.How many gold atoms are in an 0.351-ounce, 18 K gold bracelet? (18 K gold is 75% gold by mass.)
A compound whose empirical formula is XF3 consists of 65 % F by mass.What is the atomic mass of X?
A compound isolated from the rind of lemons is found to be 88.14 % carbon and 11.86 % hydrogen by mass.How many grams of H are there in a 100.1-g sample of this substance?
A compound isolated from the rind of lemons is found to be 88.14 % carbon and 11.86 % hydrogen by mass.How many moles of H?
Silver chloride, often used in silver plating, contains 75.27% Ag.Calculate the mass of silver chloride required to plate 215 mg of pure silver.
Glycine, an amino acid used by organisms to make proteins, is represented by the molecular model below. Calculate the percent nitrogen by mass in glycine.
When 13.63 g (about one tablespoon) of table sugar (sucrose, C12H22O11) is dissolved in 241.5 mL of water (density 0.997 g/mL), the final volume is 250.0 mL (about one cup).What is the mass percent of the table sugar?
Determine the chemical formula of each of the following compounds and then use it to calculate the mass percent composition of each constituent element.potassium chromate
Determine the chemical formula of each of the following compounds and then use it to calculate the mass percent composition of each constituent element.lead(II) phosphate
Determine the chemical formula of each of the following compounds and then use it to calculate the mass percent composition of each constituent element.sulfurous acid
Determine the chemical formula of each of the following compounds and then use it to calculate the mass percent composition of each constituent element.cobalt(II) bromide
Most fertilizers consist of nitrogen-containing compounds such as NH3, CO(NH2 )2, NH4 NO3, and (NH4 )2 SO4. Plants use the nitrogen content in these compounds for protein synthesis.Calculate the mass percent composition of nitrogen in NH3.
Most fertilizers consist of nitrogen-containing compounds such as NH3, CO(NH2 )2, NH4 NO3, and (NH4 )2 SO4. Plants use the nitrogen content in these compounds for protein synthesis.Which fertilizer has the highest nitrogen content?
Most fertilizers consist of nitrogen-containing compounds such as NH3, CO(NH2 )2, NH4 NO3, and (NH4 )2 SO4. Plants use the nitrogen content in these compounds for protein synthesis.Calculate the mass percent composition of nitrogen in CO(NH2 )2.
Most fertilizers consist of nitrogen-containing compounds such as NH3, CO(NH2 )2, NH4 NO3, and (NH4 )2 SO4. Plants use the nitrogen content in these compounds for protein synthesis.Calculate the mass percent composition of nitrogen in NH4 NO3.
Most fertilizers consist of nitrogen-containing compounds such as NH3, CO(NH2 )2, NH4 NO3, and (NH4 )2 SO4. Plants use the nitrogen content in these compounds for protein synthesis.Calculate the mass percent composition of nitrogen in (NH4 )2 SO4.
A metal (M) forms an oxide with the formula M2 O.If the oxide contains 16.99 % O by mass, what is the identity of the metal?
An aqueous NaCl solution is made using 126 g of NaCl diluted to a total solution volume of 1.15 L .Calculate the mass percent of the solution. (Assume a density of 1.08 g/mL for the solution.)
Lead is a toxic metal that affects the central nervous system. A Pb-contaminated water sample contains 0.0012 % Pb by mass.How much of the water (in mL) contains 155 mg of Pb? (Assume a density of 1.0 g/mL.)
How much dry solute would you take to prepare each of the following solutions from the dry solute and the solvent?126 g of 5.1 % KCl solution by mass
A mixture of CaCO3 and (NH4 )2 CO3 is 61.1 % CO3 by mass.Find the mass percent of CaCO3 in the mixture.
How much dry solute would you take to prepare each of the following solutions from the dry solute and the solvent?126 g of 1.6 % NaNO3 solution by mass
A sulfuric acid solution containing 571.5 g of H2 SO4 per liter of aqueous solution has a density of 1.329 g/cm3.Calculate the mass percentage of H2 SO4 in this solution.
A particular coal contains 2.55% sulfur by mass. When the coal is burned, it produces SO2 emissions which combine with rainwater to produce sulfuric acid.Use the formula of sulfuric acid to calculate the mass percent of S in sulfuric acid.
Without doing any calculations, arrange the elements in CaCO3 in order of decreasing mass percent composition.
Calculate the number of moles of solute present in each of the following aqueous solutions.125.0 g of a solution that is 6.50% glucose (C6 H12 O6 ) by mass.
Describe how you would prepare each of the following aqueous solutions, starting with solid KBr.1.80 L of a solution that is 13.0 % KBr by mass (the density of the solution is 1.10 g/mL)
What is the mass percentage of iodine (I2) in a solution containing 4.5×10−2 mol I2 in 125 g of CCl4?
Without doing any calculations, determine which element in each of the following compounds will have the highest mass percent composition.CO
Without doing any calculations, determine which element in each of the following compounds will have the highest mass percent composition.N2O
Calculate the percentage by mass of oxygen in the following compounds.tetracycline, C22H24N2O8
Without doing any calculations, determine which element in each of the following compounds will have the highest mass percent composition.C6H12O6
Calculate the percentage by mass of oxygen in the following compounds.digitoxin, C41H64O13
Without doing any calculations, determine which element in each of the following compounds will have the highest mass percent composition.NH3
Based on the following structural formulas, calculate the percentage of carbon by mass present in each compound. Vanillin (vanilla flavor)
Based on the following structural formulas, calculate the percentage of carbon by mass present in each compound. Isopentyl acetate (banana flavor)
Water softeners often replace calcium ions in hard water with sodium ions. Since sodium compounds are soluble, the presence of sodium ions in water does not cause the white, scaly residues caused by calcium ions. However, calcium is more beneficial to human health than sodium because calcium is a necessary part of the human diet, while high levels of sodium intake are linked to increases in blood pressure. The U.S. Food and Drug Administration (FDA) recommends that adults ingest less than 2.4 g of sodium per day.How many liters of softened water, containing a sodium concentration of 5.1×10−2 % sodium by mass, have to be consumed to exceed the FDA recommendation? (Assume a water density of 1.0 g/mL.)
Three common hydrocarbons that contain four carbons are listed here, along with their standard enthalpies of formation: Hydrocarbon Formula Hf(kJ/mol) 1,3-Butadiene C4 H6 (g) 111.9 1-Butene C4 H8 (g) 1.2 n-Butane C4 H10 (g) -124.7 For 1,3-Butadien determine the percentage of hydrogen by mass.
Three common hydrocarbons that contain four carbons are listed here, along with their standard enthalpies of formation: Hydrocarbon Formula Hf(kJ/mol) 1,3-Butadiene C4 H6 (g) 111.9 1-Butene C4 H8 (g) 1.2 n-Butane C4 H10 (g) -124.7 For 1-Butene determine the percentage of hydrogen by mass.
Three common hydrocarbons that contain four carbons are listed here, along with their standard enthalpies of formation: Hydrocarbon Formula Hf(kJ/mol) 1,3-Butadiene C4 H6 (g) 111.9 1-Butene C4 H8 (g) 1.2 n-Butane C4 H10 (g) -124.7 For n-Butane determine the percentage of hydrogen by mass.
A hard water sample contains 8.5×10−3 % Ca by mass (in the form of Ca2 + ions).How much water (in grams) contains 1.2 g of Ca? (1.2 g of Ca is the recommended daily allowance of calcium for adults between 19 and 24 years old.)
Calculate the mass percent composition of carbon in each the following carbon compounds.CH4
Calculate the mass percent composition of carbon in each the following carbon compounds.C2H6
Calculate the mass percent composition of carbon in each the following carbon compounds.C2H2
Calculate the mass percent composition of carbon in each the following carbon compounds.C2H5Cl
The density of air at sea level and 98 °F is about 1.20 g/L. The volume of the adult human lungs in the expanded state is about 6.0 L. Given that air is 20% oxygen by mass, compute the number of grams of oxygen in your lungs.
Calculate the mass percent composition of carbon in each carbon-containing compound:a. CH4
Calculate the mass percent composition of carbon in each carbon-containing compound:b. C2H6
Calculate the mass percent composition of carbon in each carbon-containing compound:c. C2H2
Calculate the mass percent composition of carbon in each carbon-containing compound: d. C2H5Cl
Calculate the mass percent composition of nitrogen in each nitrogen-containing compound: a. N2O
Calculate the mass percent composition of nitrogen in each nitrogen-containing compound: b. NO
Calculate the mass percent composition of nitrogen in each nitrogen-containing compound: c. NO2
Calculate the mass percent composition of nitrogen in each nitrogen-containing compound:d. HNO3
Iron from the earth is in the form of iron ore. Common ores include Fe 2O3 (hematite), Fe3O4 (magnetite), and FeCO3 (siderite). Calculate the mass percent composition of nitrogen in each of these iron ores. Which one has the highest iron content?
The molecular weight of ethanol (C2H5OH) is 46.1 and the density of absolute (100%) ethanol = 0.79 g/mL. The legal limit for a driver’s blood alcohol is 50 mg of ethanol per 100 mL of blood (referred to as a blood alcohol content (BAC) of 0.05%). And a bottle of wine is 14% ethanol by volume. How much wine (standard serving size = 100 mL) could a 75 kg person drink and remain under the legal limit? The blood alcohol content will be equivalent to the alcohol content in the total ‘water’ component of the human body. A 75 kg person contains about 40 L of ‘water’. Ignore the metabolism, and assume the water content of the person remains constant.
Copper(II) fluoride contains 37.42% F by mass. Calculate the mass of fluorine (in g) contained in 55.5 g of copper(II) fluoride.
Silver chloride, often used in silver plating, contains 75.27% Ag by mass. Calculate the mass of silver chloride required to plate 155 mg of pure silver.
Determine the chemical formula of each compound and then use it to calculate the mass percent composition of each constituent element: a. perchloric acid
Determine the chemical formula of each compound and then use it to calculate the mass percent composition of each constituent element: b. phosphorus pentachloride 
Determine the chemical formula of each compound and then use it to calculate the mass percent composition of each constituent element: c. nitrogen triiodide
Determine the chemical formula of each compound and then use it to calculate the mass percent composition of each constituent element: d. carbon dioxide 
A mixture contains only NaCl and Fe(NO 3)3. A 0.456-g sample of the mixture is dissolved in water, and an excess of NaOH is added, producing a precipitate of Fe(OH)3. The precipitate is filtered, dried, and weighed. Its mass is 0.107 g. Calculate the following. c. the mass percent of Fe(NO 3)3 in the sample
What is the mass percent of each element in sulfuric acid, H2SO4? a. 2.055% H, 32.69% S, 65.25% O b. 1.028% H, 32.69% S, 66.28% O c. 28.57% H, 14.29% S, 57.17% O d. 1.028% H, 33.72% S, 65.25% O e. 2.016% H, 32.07% S, 65.91% O  
Anabolic steroids are performance enhancement drugs whose use has been banned from most major sporting activities. One anabolic steroid is fluoxymesterone (C20H29FO3). Calculate the percent composition by mass of fluoxymesterone.
Hemoglobin is the protein that transports oxygen in mammals. Hemoglobin is 0.347% Fe by mass, and each hemoglobin molecule contains four iron atoms. Calculate the molar mass of hemoglobin.
What is the mass percentage of each element in the compound Al 2O3?
Express the composition of each of the following compounds as the mass percents of its elements.a. formaldehyde, CH2O
Express the composition of each of the following compounds as the mass percents of its elements.b. glucose, C6H12O6
Express the composition of each of the following compounds as the mass percents of its elements.c. acetic acid, HC2H3O2
Without doing any calculations, determine which element in each of the compounds will have the highest mass percent composition. a. CO
Without doing any calculations, determine which element in each of the compounds will have the highest mass percent composition. b. N2O
Without doing any calculations, determine which element in each of the compounds will have the highest mass percent composition. c. C6H12O6
Without doing any calculations, determine which element in each of the compounds will have the highest mass percent composition. d. NH3
A solution is prepared by dissolving 98.6 g of NaCl in enough water to form 875 mL of solution. Calculate the mass % of the solution if the density of the solution is 1.06 g/mL.A) 12.7%      B) 11.3%      C) 9.4%      D) 11.9%      E) 10.6%
Calculate the following:Mass % of O in sodium dihydrogen phosphate heptahydrate.
A solution was prepared by dissolving 39.0 g of  KCl in 225 mL of water. Calculate the mass percent of KCl in the solution.
Magnesium carbonate (MgCO3) and calcium carbonate (CaCO3) both decompose when heated, forming CO2 gas and the corresponding oxides.MgCO3(s) → CO2(g) + MgO(s)CaCO3(s) → CO2(g) + CaO(s)When a particular mixture of MgCO3 and CaCO3 is heated, it releases 47% of its mass as CO 2, so that the oxide products have 53% of the mass of the original sample. What mass percentage of MgCO3 was present in the original mixture?
A 5.00 g sample of a gas mixture, consisting of methane, CH4, and ethylene, C2H4, was burned in excess oxygen, yielding 14.5 g of CO2 and some amount of water as products. What mass percent of the sample was ethylene? HINT: Write and balance the chemical equation for each reaction taking place before you start working on the problem.
Coke is an impure form of carbon that is often used in the industrial production of metals from their oxides. If a sample of coke is 95% carbon by mass, determine the mass of coke needed to react completely with 1.0 ton of copper(II) oxide.2CuO(s) + C(s) → 2Cu(s) + CO2(g) 
2.489 g of cesium oxalate are dissolved in enough water to give 265.0 mL of a solution whose density is 1.0528 g/mL. What is the percent by mass concentration of the solution? (molar mass cesium oxalate = 353.83 g/mole)
Calculate the percent recovery of a component of a binary mixture that weighs 0.2 grams. The mass of the mixture before separating the components of the mixture was 304 grams. A.0.0065789 % B.65.789 % C.6.6 x 104 % D.6.6 x 10-2 %
Many cereals are made with high moisture content so that the cereal can be formed into various shapes before it is dried. A cereal product containing 58% H2O by mass is produced at the rate of 1000 kg/hr. 
A sample of LSD (D-lysergic acid diethylamide, C24H30N3O) is added to some table salt (sodium chloride) to form a mixture. Given that a 1.00-g sample of the mixture undergoes combustion to produce 1.20 g of CO2, what is the mass percentage of LSD in the mixture?
Hemoglobin is 6.0% heme (C34H32FeN4O4) by mass. To remove the heme, hemoglobin is treated with acetic acid and NaCl, which forms hemin (C34H32N4O4FeCl). A blood sample from a crime scene contains 0.65 g of hemoglobin. (c) How many grams of Fe are in the sample?
Hemoglobin, the oxygen-carrying protein in red blood cells, has four iron atoms per molecule and contains 0.340% iron by mass. Calculate the molar mass of hemoglobin.
A typical formulation for window glass is 75% SiO2, 15% Na2O, and 10.% CaO by mass. What masses of sand (SiO2), sodium carbonate, and calcium carbonate must be combined to produce 1.00 kg of glass after carbon dioxide is driven off by thermal decomposition of the carbonates?
Hydrocarbon mixtures are used as fuels. (a) How many grams of CO 2(g) are produced by the combustion of 200. g of a mixture that is 25.0% CH4 and 75.0% C3H8 by mass?
The active compound in Pepto-Bismol contains C, H, O, and Bi.c) Complete and balance the acid-base reaction between bismuth(III) hydroxide and salicylic acid (HC7H5O3), which is used to form this compound. d) A dose of Pepto-Bismol contains 0.600 mg of active ingredient. If the yield of the reaction in part (c) is 88.0%, what mass (in mg) of bismuth(III) hydroxide is required to prepare one dose?
The space shuttle environmental control system handles excess CO2 (which the astronauts breathe out; it is 4.0% by mass of exhaled air) by reacting it with lithium hydroxide, LiOH, pellets to form lithium carbonate, Li2CO3, and water. If there are seven astronauts on board the shuttle, and each exhales 20. L of air per minute, how long could clean air be generated if there were 25,000 g of LiOH pellets available for each shuttle mission? Assume the density of air is 0.0010 g/mL.
Lead is found in Earths crust as several different lead ores. Suppose a certain rock is composed of 38.0% PbS (galena), 25.0% PbCO3 (cerussite), and 17.4% PbSO4 (anglesite). The remainder of the rock is composed of substances containing no lead.How much of this rock (in kg) must be processed to obtain 5.1 metric tons of lead? (A metric ton is 1000 kg.)
Calculate the number of moles of solute present in 80.0 g of an aqueous solution that is 1.60 % sucrose (C12H22O11) by mass.
Fungal laccase, a blue protein found in wood-rotting fungi, is 0.390% Cu by mass. If a fungal laccase molecule contains four copper atoms, what is the molar mass of fungal laccase?
Copper(I) iodide (CuI) is often added to table salt as a dietary source of iodine. How many moles of CuI are contained in 1.00 lb (454 g) of table salt containing 0.0100% CuI by mass?
Hemoglobin is the protein that transports oxygen in mammals. Hemoglobin is 0.347% Fe by mass, and each hemoglobin molecule contains four iron atoms. Calculate the molar mass of hemoglobin.
Citric acid (below) is concentrated in citrus fruits and plays a central metabolic role in nearly every animal and plant cell. (b) How many moles of citric acid are in 1.50 qt of lemon juice (d=1.09 g/mL) that is 6.82% citric acid by mass?
Many cereals are made with high moisture content so that the cereal can be formed into various shapes before it is dried. A cereal product containing 58% H2O by mass is produced at the rate of 1000. kg/h. What mass of water must be evaporated per hour if the final product contains only 20.% water?
A compound containing only sulfur and nitrogen is 69.6% S by mass; the molar mass is 184 g/mol. What are the empirical and molecular formulas of the compound?
Determine the molecular formula of a compound that contains 26.7% P, 12.1% N, and 61.2% Cl, and has a molar mass of 580 g/mol.
Vitamin B12, cyanocobalamin, is essential for human nutrition. It is concentrated in animal tissue but not in higher plants. Although nutritional requirements for the vitamin are quite low, people who abstain completely from animal products may develop a deficiency anemia. Cyanocobalamin is the form used in vitamin supplements. It contains 4.34% cobalt by mass. Calculate the molar mass of cyanocobalamin, assuming that there is one atom of cobalt in every molecule of cyanocobalamin.
Some bismuth tablets, a medication used to treat upset stomachs, contain 262 mg of bismuth subsalicylate, C7H5BiO4, per tablet. Assuming two tablets are digested, calculate the mass of bismuth consumed.
Maleic acid is an organic compound composed of 41.39% C, 3.47% H, and the rest oxygen. If 0.129 mole of maleic acid has a mass of 15.0 g, what are the empirical and molecular formulas of maleic acid?
What mass (in grams) of iron(III) oxide contains 58.8 g of iron? Iron(III) oxide is 69.94 % iron by mass.
If someone consumes 23 g of sodium chloride per day, what mass (in grams) of sodium does that person consume? Sodium chloride is 39 % sodium by mass.
A compound isolated from the rind of lemons is found to be 88.14 % carbon and 11.86 % hydrogen by mass.How many moles of C?
Solar winds composed of free protons, electrons, and α particles bombard Earth constantly, knocking gas molecules out of the atmosphere. In this way, Earth loses about 3.0 kg of matter per second. It is estimated that the atmosphere will be gone in about 50 billion years. Use this estimate to calculate the amount (mol) of nitrogen, which makes up 75.5 mass % of the atmosphere.
The American Dental Association recommends that an adult female should consume 3.0 mg of fluoride (F–) per day to prevent tooth decay. If the fluoride is consumed as sodium fluoride (45.24% F), what amount of sodium fluoride contains the recommended amount of fluoride?
Commercial brass, an alloy of Zn and Cu, reacts with hydrochloric acid as follows:Zn (s) + 2 HCl (aq) → ZnCl 2 (aq) + H2 (g) (Cu does not react with HCl.)When 0.5065 g of a certain brass alloy is reacted with excess HCl, 0.0985 g ZnCl  2 is eventually isolated. How could this result be checked without changing the above procedure?
Ammonium dihydrogen phosphate, formed from the reaction of phosphoric acid with ammonia, is used as a crop fertilizer as well as a component of some fire extinguishers. (b) How much ammonia is incorporated into 100 g of the compound?
Hemoglobin, a protein in red blood cells, carries O 2 from the lungs to the body’s cells. Iron (as ferrous ion, Fe2+) makes up 0.33 mass % of hemoglobin. If the molar mass of hemoglobin is 6.8×104 g/mol, how many Fe2+ ions are in one molecule?
Hemoglobin is 6.0% heme (C34H32FeN4O4) by mass. To remove the heme, hemoglobin is treated with acetic acid and NaCl, which forms hemin (C34H32N4O4FeCl). A blood sample from a crime scene contains 0.65 g of hemoglobin.(a) How many grams of heme are in the sample?
The iodide ion is a dietary mineral essential to good nutrition. In countries where potassium iodide is added to salt, iodine deficiency or goiter has been almost completely eliminated. The recommended daily allowance (RDA) for iodine is 150 µg/day. How much potassium iodide (76.45% I) should be consumed to meet the RDA?
Nitrogen forms more oxides than any other element. The percents by mass of N in three different nitrogen oxides are (I) 46.69%, (II) 36.85%, and (III) 25.94%. For each compound, determine (b) the number of grams of oxygen per 1.00 g of nitrogen.
Hemoglobin is 6.0% heme (C34H32FeN4O4) by mass. To remove the heme, hemoglobin is treated with acetic acid and NaCl, which forms hemin (C34H32N4O4FeCl). A blood sample from a crime scene contains 0.65 g of hemoglobin.(b) How many moles of heme are in the sample?
Calculate the mass percentage of NaCl in a solution containing 1.50 g of NaCl in 50.0 g of water.
The nitrogen in sodium nitrate and in ammonium sulfate is available to plants as fertilizer. Which is the more economical source of nitrogen, a fertilizer containing 30.0% sodium nitrate by weight and costing $9.00 per 100 lb or one containing 20.0% ammonium sulfate by weight and costing $8.10 per 100 lb.
Hemoglobin is 6.0% heme (C34H32FeN4O4) by mass. To remove the heme, hemoglobin is treated with acetic acid and NaCl, which forms hemin (C34H32N4O4FeCl). A blood sample from a crime scene contains 0.65 g of hemoglobin.(d) How many grams of hemin could be formed for a forensic chemist to measure?
Calculate the mass percent composition of each constituent element of potassium chromate.
Calculate the mass percent composition of each constituent element of lead(II) phosphate.
Calculate the mass percent composition of each constituent element of sulfurous acid.
Arrange the following substances in order of increasing mass percent of nitrogen.a. NO             c. NH  3b. N2O           d. SNH
Calculate the mass percent composition of each constituent element of cobalt(II) bromide.
The seven most abundant ions in seawater make up more than 99% by mass of the dissolved compounds. Here are their abundances in units of mg ion/kg seawater: chloride 18,980; sodium 10,560; sulfate 2650; magnesium 1270; calcium 400; potassium 380; hydrogen carbonate 140.(a) What is the mass % of each ion in seawater?
The seven most abundant ions in seawater make up more than 99% by mass of the dissolved compounds. Here are their abundances in units of mg ion/kg seawater: chloride 18,980; sodium 10,560; sulfate 2650; magnesium 1270; calcium 400; potassium 380; hydrogen carbonate 140.(b) What percent of the total mass of ions is represented by sodium ions?
Calculate the mass percent composition of each constituent element of perchloric acid.
Calculate the mass percent composition of each constituent element of phosphorus pentachloride.
The seven most abundant ions in seawater make up more than 99% by mass of the dissolved compounds. Here are their abundances in units of mg ion/kg seawater: chloride 18,980; sodium 10,560; sulfate 2650; magnesium 1270; calcium 400; potassium 380; hydrogen carbonate 140.(c) How does the total mass % of alkaline earth metal ions compare with the total mass % of alkali metal ions?
Calculate the mass percent composition of each constituent element of nitrogen triiodide.
The seven most abundant ions in seawater make up more than 99% by mass of the dissolved compounds. Here are their abundances in units of mg ion/kg seawater: chloride 18,980; sodium 10,560; sulfate 2650; magnesium 1270; calcium 400; potassium 380; hydrogen carbonate 140.(d) Which make up the larger mass fraction of dissolved components, anions or cations?
Calculate the mass percent composition of each constituent element of carbon dioxide.
A metal (M) forms a compound with the formula MCl3.If the compound contains 65.57 % Cl by mass, what is the identity of the metal?
Succinic acid (below) is an important metabolite in biological energy production. Give the molecular formula, molecular mass, and the mass percent of each element in succinic acid.
A dioxin-contaminated water source contains 0.086 % dioxin by mass. How much dioxin is present in 2.6 L of this water? Assume a density of 1.00 g/mL.
Fluorite, a mineral of calcium, is a compound of the metal with fluorine. Analysis shows that a 2.76-g sample of fluorite contains 1.42 g of calcium. Calculate the (b) mass fractions of calcium and fluorine in fluorite; 
Fluorite, a mineral of calcium, is a compound of the metal with fluorine. Analysis shows that a 2.76-g sample of fluorite contains 1.42 g of calcium. Calculate the (c) mass percents of calcium and fluorine in fluorite.
Galena, a mineral of lead, is a compound of the metal with sulfur. Analysis shows that a 2.34-g sample of galena contains 2.03 g of lead. Calculate the (b) mass fractions of lead and sulfur in galena; 
Galena, a mineral of lead, is a compound of the metal with sulfur. Analysis shows that a 2.34-g sample of galena contains 2.03 g of lead. Calculate the (c) mass percents of lead and sulfur in galena.
Hydrocarbon mixtures are used as fuels. (b) A 252-g gaseous mixture of CH 4 and C3H8 burns in excess O 2, and 748 g of CO2 gas is collected. What is the mass % of CH 4 in the mixture?
Nitrogen (N), phosphorus (P), and potassium (K) are the main nutrients in plant fertilizers. By industry convention, the numbers on a label refer to the mass percents of N, P2O5, and K2O, in that order. Calculate the N/P/K ratio of a 30/10/10 fertilizer in terms of moles of each element, and express it as x/y/1.0.
List the elements in the compound CF2Cl2 in order of decreasing mass percent composition.
Manganese is a key component of extremely hard steel. The element occurs naturally in many oxides. A 542.3-g sample of a manganese oxide has an Mn/O ratio of 1.00/1.42 and consists of braunite (Mn2O3) and manganosite (MnO).(b) What is the Mn3+/Mn2+ ratio in the ore?
The human body excretes nitrogen in the form of urea, NH2CONH2. The key step in its biochemical formation is the reaction of water with arginine to produce urea and ornithine:(a) What is the mass % of nitrogen in urea, in arginine, and in ornithine?
Calculate the percent composition by mass of the following compound that is an important starting material for synthetic polymers: C3H4O2 (acrylic acid, from which acrylic plastics are made).
Nitrogen (N), phosphorus (P), and potassium (K) are the main nutrients in plant fertilizers. By industry convention, the numbers on a label refer to the mass percents of N, P2O5, and K2O, in that order.What mass percents of ammonium sulfate, ammonium hydrogen phosphate, and potassium chloride would you use to prepare 10/10/10 plant fertilizer?
Calculate the percent composition by mass of the following compound that is an important starting material for synthetic polymers: C4H6O2 (methyl acrylate, from which Plexiglas is made).
A solution is made containing 21.2 g phenol (C6H5OH) in 450 g ethanol (CH3 CH2OH).Calculate the mass percent of phenol.
Calculate the percent composition by mass of the following compound that is an important starting material for synthetic polymers: C3H3N (acrylonitrile, from which Orlon is made)
In 1987 the first substance to act as a superconductor at a temperature above that of liquid nitrogen (77 K) was discovered. The approximate formula of this substance is YBa2Cu3O7. Calculate the percent composition by mass of this material.
Without doing any calculations, list the elements in C6H6O in order of decreasing mass percent composition.
Calculate the percentage by mass of oxygen in the following compounds.morphine, C17H19NO3
Calculate the percentage by mass of oxygen in the following compounds.cocaine, C17H21NO4
Describe how you would prepare each of the following aqueous solutions.Give the mass of the solute and mass of the solvent for 1.30 L of a solution that is 16.0 % of Pb(NO3 )2 by mass (the density of the solution is 1.16 g/mL), starting with solid solute.
When carbon-containing compounds are burned in a limited amount of air, some CO(g) as well as CO2(g) is produced. A gaseous product mixture is 35.0 mass % CO and 65.0 mass % CO2. What is the mass % of C in the mixture?
Acetic acid (HC2H3O2) is the active ingredient in vinegar. Calculate the mass percent composition of oxygen in acetic acid.
Calculate the percentage by mass of the indicated element in the following compounds.Carbon in acetylene, C2H2, a gas used in welding       
Calculate the percentage by mass of the indicated element in the following compounds.Hydrogen in ascorbic acid, HC6H7O6, also known as vitamin C      
Calculate the percentage by mass of the indicated element in the following compounds.Hydrogen in ammonium sulfate, (NH4)2SO4, a substance used as a nitrogen fertilizer      
Calculate the percentage by mass of the indicated element in the following compounds.Platinum in PtCl2(NH3)2, a chemotherapy agent called cisplatin        
Arrange the following substances in order of increasing mass percent of carbon.a. caffeine, C8H10N4O2b. sucrose, C12H22O11c. ethanol, C2H5OH
Calculate the percentage by mass of the indicated element in the following compounds.Oxygen in the female sex hormone estradiol, C18H24O2
Calculate the percentage by mass of the indicated element in the following compounds.Carbon in capsaicin, C18H27NO3, the compound that gives the hot taste to chili peppers        
Based on the following structural formulas, calculate the percentage of carbon by mass present in each compound.
Calculate the mass percent composition of sodium in sodium oxide.
Express the composition of formaldehyde, CH2O, as the mass percents of its elements.
Calculate the following to four significant figures: (a) the percent composition of ammonia, NH3 
Calculate the following to four significant figures:(b) the percent composition of photographic fixer solution (“hypo”), Na2S2O3 
Calculate the following to four significant figures:(c) the percent of calcium ion in Ca3(PO4)2
Express the composition of glucose, C6H12O6, as the mass percents of its elements.
Express the composition of acetic acid, HC 2H3O2, as the mass percents of its elements.
Determine the following to four significant figures: (a) the percent composition of hydrazoic acid, HN3 
Determine the following to four significant figures:(b) the percent composition of TNT, C6H2(CH3)(NO2)3 
Determine the following to four significant figures:(c) the percent of SO4 2– in Al2(SO4)3
Determine the percent water in CuSO4∙5 H2O to three significant figures
Hydrogen-containing fuels have a “fuel value” based on their mass % H. Rank the following compounds from highest fuel value to lowest: ethane, propane, benzene, ethanol, cetyl palmitate (whale oil, C32H64O2).
Anabolic steroids are performance enhancement drugs whose use has been banned from most major sporting activities. One anabolic steroid is fluoxymesterone (C20H29FO3). Calculate the percent composition by mass of fluoxymesterone.
Calculate the percentage of carbon by mass in each of the compounds represented by the following models. (Carbon atoms are black spheres, hydrogen are grey, oxygen are red.)
Calculate the percentage of carbon by mass in each of the compounds represented by the following models. (Carbon atoms are black spheres, hydrogen are grey, oxygen are red.)
Calculate the percentage of carbon by mass in each of the compounds represented by the following models. (Carbon atoms are black spheres, hydrogen are grey, oxygen are red.)
Nitrogen monoxide (NO) is a bioactive molecule in blood. Low NO concentrations cause respiratory distress and the formation of blood clots. Doctors prescribe nitroglycerin, C3H5N3O9, and isoamyl nitrate, (CH3)2CHCH2CH2ONO2, to increase the blood level of NO. If each compound releases one molecule of NO per atom of N it contains, calculate the mass percent of NO in each.
The anticancer drug Platinol (cisplatin), Pt(NH3)2Cl2, reacts with a cancer cell’s DNA and interferes with its growth. (a) What is the mass % of platinum (Pt) in Platinol? 
A potassium bromide solution is 7.55% potassium bromide by mass and its density is 1.03 g/mL. What mass of potassium bromide is contained in 35.8 mL of the solution?
Calculate the following;Mass % of H in ammonium bicarbonate
A sample of LSD (D-lysergic acid di