2 H2 (g) + O2 (g) --> 2 H20 (g) How many grams of hydrogen are necessary to react with 15.0 g of oxygen?

What is important to study for nios grade 12 chemistry? i have only one month left.

Harvey kept a balloon with a volume of 348 milliliters at 25.0˚c inside a freezer for a night.  when he took it out, its new volume was 322 milliliters, but its pressure was the same.  if the final temperature of the balloon is the same as the freezer’s, what is the temperature of the freezer? the temperature of the freezer is  kelvins.

Under normal conditions, describe how increasing the temperatures effects the solubility of a typical salt