PLS HELP ME I WILL GIVE BRAIN THINGY

Seawater contains approximately 3.5%nacl by mass and has a density of 1.02 g/ml. what volume of seawater contains 7.5 g of sodium?

Determine the wavelength of the light absorbed when an electron in a hydrogen atom makes a transition from an orbital in the n=3 level to an orbital in the n=7 level.

Which of these is not an example of chemical weathering? a. iron-rich mineral rusting b. feldspar turning into clay c. limestone reacting with acid d. granite breaking up into sand