In an industrial process, 200. L of a gas at 91.0 kPa and 21.0 °C is compressed into a vessel that has a volume of 15.2 L and heated to 420. °C. What is its final pressure?

The answer for #3 is c but i don't know why

Calculate the ratio of h+ ions to oh– ions at a ph = 7. find the concentration of h+ ions to oh– ions listed in table b of your student guide. then divide the h+ concentration by the oh– concentration. record this calculated ratio in table a of your student guide. compare your approximated and calculated ratios of h+ ions to oh– ions at a ph = 7. are they the same? why or why not? record your comparison in table a. what is the concentration of h+ ions at a ph = 7? mol/l what is the concentration of oh– ions at a ph = 7? mol/l what is the ratio of h+ ions to oh– ions at a ph = 7? : 1

Suppose you wanted to make 100 grams of water. what is the molar mass of water (h2o)?