24%

49%

51%

65%

20%

27%

46%

53%

is composed of only hydrogen and oxygen

is a state of water

contains water in the compound

repels water from the compound

Add up the mass of protons and neutrons, then divide by two.

Divide the mass of the element by the total mass of the compound and multiply by 100.

Add up the atomic masses of the elements, then divide by the number of the elements.

Find the relative mass of any atom by adding the number of protons to the number of neutrons, then dividing by that total number.