I'm on a pay phone trying to... GET MCAT HELP!

[SonhosDaVida]

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The main contributors to atmospheric pressure are nitrogen and oxygen. The contribution of water vapor is the greatest at sea level, and trace amounts of other gasses also contribute to a small degree. A closed container holds four gases: 1 mole of Gas A, 1 mole of Gas B, 3 moles of Gas C, and 4 moles of Gas D. If the total pressure inside the container is 3 atm, what is the partial pressure of Gas C?

1. C0.33 atm
2. 1 atm
3. 1.33 atm
4. 9 atm

Where in the question is the pressure of te closed contained given as 3atm? Answer is 2, don't know why

 

[ChrisMack390]

What?

1 + 1 + 3 + 4 = 9 atm total

3 atm C / 9 atm total = 0.333 contribution from gas C

0.333 x 3 atm = 1 atm

 

[bee17]

The questions says "If the total pressure inside the container is 3 atm..."

This means you must assume that total pressure = 3 atm for this question. There are 9 moles of gas total (1+1+3+4=9) and 3 of those moles are from Gas C. That means 1/3 of the moles are Gas C, so the partial pressure of Gas C will be 1/3 of the total pressure. 1/3 of 3 atm is 1 atm.