We’re being asked to calculate the percent chlorine (by mass) in the unknown chlorofluorocarbon.

**Decomposition reaction: CHFCl _{(g)}**

*We’re going to **calculate the percent chlorine (by mass) in the unknown chlorofluorocarbon using the following steps.*

*Step 1**. Calculate the moles of Cl _{2} produced using the ideal gas equation.*

$\overline{){\mathbf{PV}}{\mathbf{=}}{\mathbf{nRT}}}$

P = pressure, atm

V = volume, L

n = moles, mol

R = gas constant = 0.08206 (L·atm)/(mol·K)

T = temperature, K

**Step 2**. Calculate the mass of Cl_{2} produced using its molar mass.

**Step 3**. Calculate the percent chlorine (by mass) in the unknown chlorofluorocarbon.

A 2.90 -g sample of an unknown chlorofluorocarbon is decomposed and produces 572 mL of chlorine gas at a pressure of 754 mm Hg and a temperature of 298 K.

What is the percent chlorine (by mass) in the unknown chlorofluorocarbon?

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Gas Stoichiometry concept. If you need more Gas Stoichiometry practice, you can also practice Gas Stoichiometry practice problems.