A chemist determined that a sample contains 20 g of hydrogen and 320 g of oxygen. Is this sample water, or is it hydrogen peroxide?

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

24. a sports ball is inflated to an internal pressure of 1.85 atm at room temperature (25 °c). if the ball is then played with outside where the temperature is 7.5 °c, what will be the new pressure of the ball? assume the ball does not change in volume nor does any air leak from the ball a) 0.555 atm b) 1.74 atm c) 1.85 atm d) 1.97 atm

An alloy contains 66 g of pure zinc. what is the percentage of zinc in the alloy? express your answer to two significant figures and include the appropriate units.