Chemistry problem involving gas laws

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Discussion Overview

The discussion revolves around a chemistry problem involving gas laws, specifically the decomposition of an unknown chlorofluorocarbon and the calculation of the percent chlorine by mass in the compound. The scope includes mathematical reasoning and problem-solving related to gas laws and molar mass calculations.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant presents a problem involving the decomposition of a chlorofluorocarbon, using the ideal gas law (PV=nRT) to calculate the number of moles of chlorine gas produced.
  • The same participant attempts to derive the molar mass of the chlorofluorocarbon and sets up an equation to find the mass percent of chlorine, but reports an incorrect result.
  • Another participant suggests calculating the grams of chlorine in the moles obtained, prompting a comparison with the total mass of the sample.
  • A subsequent reply questions the availability of the grams of chlorine, indicating a lack of clarity on the information needed for the calculation.
  • Another participant clarifies that the grams of chlorine can be determined from the moles and the molar mass of chlorine.
  • The initial poster expresses gratitude and indicates they have resolved their confusion.

Areas of Agreement / Disagreement

The discussion shows a progression from confusion to resolution for the initial poster, but it does not indicate a consensus on the overall approach or final calculations, as the correctness of the initial calculations remains unverified.

Contextual Notes

There are limitations regarding the assumptions made in the calculations, particularly concerning the molar masses used and the setup of the algebraic equation for mass percent. The discussion does not resolve these aspects.

Who May Find This Useful

Students or individuals interested in gas laws, stoichiometry, and mass percent calculations in chemistry may find this discussion relevant.

MellowOne
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A 2.80g sample of an unknown chlorofluorocarbon is decomposed and produces 552mL of chlorine gas at a pressure of 756 mmHg and a temperature of 298K.
What is the percent chlorine (by mass) in the unknown chlorofluorocarbon? PV= nRT
D= m/vOk, so for this problem I tried using the PV=nRT (756*.552=n*62.364*298) equation to solve for n and I got 0.02245 mol. And from that, I figured the molar mass was 124.69 g/mol (having used the mass of 2.80 to derive this answer). And then I tried to set up an algebraic equation with variables to solve for the mass percent. I used the equation (1-x)(31.008) + 35.45x = 124.69. The (1-x) represents the Carbon and Fluorine components of the compound, and the 31.008 is their combined molar mass. The 35.45 is the molar mass of Clorine, and by solving this equation i got 21.09, but this was incorrect. So what should i do?
 
Last edited:
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How many grams of chlorine are in 0.02245 mol of Cl2?

Compare that to 2.80 g.
 
but we don't know how many grams we have of chlorine...?
 
You know how many moles and how many grams/mole for chlorine. Use that.
 
okay thank you i got it!
 

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