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

Solution: An unknown compound contains only carbon and hydrogen. When it undergoes combustion analysis, it produces 3.767 g of CO2 and 0.616 g of H2O. What is the empirical formula? a. C7H14 b. CH4 c. C2H3d. CHe. C5H4

Problem

An unknown compound contains only carbon and hydrogen. When it undergoes combustion analysis, it produces 3.767 g of CO2 and 0.616 g of H2O. What is the empirical formula? 

a. C7H14 

b. CH4 

c. C2H3

d. CH

e. C5H4

Solution

We’re being asked to determine the empirical formula of a compound composed of C and H given the combustion analysis.


Recall that in combustion analysisa compound reacts with excess O2 to form products. For a compound composed only of C and H, the reaction looks like this:


CxHy + O2 (excess)  x CO2y/2 H2O


This means we need to do the following steps:

Step 1: Calculate the moles of C and H in the compound.

Step 2: Determine the lowest whole number ratio of C and H to get the empirical formula.


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