2.3 Exercise 11

Heliox, a mixture of helium and oxygen, is sometimes given to hospital patients who have trouble breathing, because the low mass of helium makes it easier to breathe than air. Suppose helium at $25 °\text{C}$ is mixed with oxygen at $35 °\text{C}$ to make a mixture that is $70 \%$ helium by mole. What is the final temperature? Ignore any heat flow to or from the surroundings, and assume the final volume is the sum of the initial volumes.