How does temperature, water vapor, and elevation affect air pressure?

Chemistry worksheet - i am not sure what they are asking for exactly?

At a certain temperature the rate of this reaction is first order in hi with a rate constant of : 0.0632s2hig=h2g+i2g suppose a vessel contains hi at a concentration of 1.28m . calculate how long it takes for the concentration of hi to decrease to 17.0% of its initial value. you may assume no other reaction is important. round your answer to 2 significant digits.

Which of the following substances is the most soluble in water? a. sodium chloride b. methane c. bromine d. carbon