chemistry
posted by Sam .
A gaseous mixture at a total pressure of 1.50 atm contains equal molar amounts of He, Ne, and Ar. At constant temperature CO2 gas is added to the mixture until the total pressure is 3.00 atm. Which of the following is a correct statement concerning partial pressures after the CO2 addition?
a. the original partial pressures of He, Ne, and Ar have been cut in half
b. the partial pressure of CO2 is three times that of Ne
c. all four gases have equal partial pressures
d. the partial pressure of Ar has doubled

a. the original partial pressures of He, Ne, and Ar have been cut in half
b. the partial pressure of CO2 is three times that of Ne
c. all four gases have equal partial pressures
d. the partial pressure of Ar has doubled 
the original partial pressures of He, Ne, and Ar have been cut in half
the partial pressure of CO2 is three times that of Ne
all four gases have equal partial pressures
the partial pressure of Ar has doubled 
Why don't you try calculating it and see what happens.
Total P = 1.5 atm, assume any volume (but always use the same one1 L is the most convenient) and calculate n = mols gas. Since He, Ne, and Ar are equimolar, divide n/3 will be the mols of each of He, Ne, and Ar.
Then introduce CO2 (You are putting 1.5 atm CO2 in, keep the same conditions) and calculate mols CO2, then pressure of CO2. Then you will know the answer. I can help you through if you get stuck. 
A mixture of gases contains twice as many moles of As as Kr. If 0.300 mol of Xe is added to this mixture, the pressure increases from 1.26 atm to 1.47 atm. how many moles of Ar are in the mixture?