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: A sample of gas has a mass of 38.8 mg . Its volume is 226 mL at a temperature of 56 oC and a pressure of 860 torr .Find the molar mass of the gas.

Problem

A sample of gas has a mass of 38.8 mg . Its volume is 226 mL at a temperature of 56 oC and a pressure of 860 torr .

Find the molar mass of the gas.

Solution

We’re being asked to determine the molecular weight of the unknown gas. 

Recall that molecular weight is in grams per 1 mole of a substance.

Molecular Weight (MW)=gmol


Step1: First, we have to calculate the amount of gas in moles using the ideal gas equation.

PV=nRT

P = pressure, atm
V = volume, L
n = moles, mol
R = gas constant = 0.08206 (L·atm)/(mol·K)
T = temperature, K


Isolate n (number of moles of gas): 

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