A gas cylinder contains 2.0 mol of gas X and 6.0 mol of gas Y at a total pressure of 2.1 atm. What is is partial pressure of gas Y?
1 Answer
Explanation:
Okay, so here is what is going on.
You have some gas cylinder which contains a mixture of 2 different gases:
Write out our givens.
Given
#"2.0 moles of gas X"# #"6.0 moles of gas Y"# #"Total pressure = 2.1 atm"#
To find the partial pressure of
Where

#"P"_"Y" = "partial pressure of gas Y"# 
#"P"_"T" = "total pressure"# 
#"x"_"Y" = "mole fraction of gas Y"#
We were given the total pressure of the system, but we need to figure out the mole fraction of gas Y. To calculate it, we use the following equation:
Plugin and solve for the mole fraction of gas Y

#color(blue)[x_"Y" = ("moles of gas Y")/("total moles of gas")#
#color(white)()# 
#rarr("6.0 moles of gas Y")/("2.0 moles of gas X + 6.0 moles of gas Y")# 
#rarr("6" cancel"moles")/("8" cancel"moles")# 
#rarrcolor(red)" 0.75"#
Note: moles over moles cancel out so the mole fraction is unitless
You now can use the mole fraction to solve for the partial pressure of gas Y by using the first equation which was given out.
#color(blue)[P_"Y" = P_"T" * x_"Y"# #P_"Y" = "(2.1 atm)" * "(0.75)"# #P_"Y" = color(magenta)"1.58 atm"#
Answer: