Any help would be great on the below problems. I am not sure where to begin. How do I solve these? Do I use a formula?

Question

1. You are asked to make 500.0 mL of a 4.5M solution of HCl, but the only HCl you have available to dilute is 18.0M. Describe how you would make the desired solution. Show any math work and equations used.

2. A bag of potato chips contains 585 mL of air at 25°C and a pressure of 765 mmHg. Assuming the bag does not break, what will its volume be at the top of the mountain where the pressure is 442 mmHg and the temperature is 5.0°C? Show your work and equations used.

Answer 1

1. mL x M = mL x M
500 x 4.5 = mL x 18.0
Solve for mL of the 18.0. Remember volumes are not additive; therefore, you can't use 125 mL of the 18.0 M stuff and add 375 mL water. The way you do it is to place 125 mL of the 18.0 stuff in a 500 mL volumetric flask and add water to the mark.

2. (P1V1/T1) = (P2V2/T2)

Answer 2

P1V1/T1 = P2V2/T2
(765 mmHg)(585mL)/298K=(442mmHg) V2/278K
V2=944.55mL
so would that be right for #2??

Thank you so much for your help, I wasn't sure which law to use.