Pls this need this I am doing a test and I need to get this

Used the balanced equation 2h2+ o2 - -> 2h2o. if you have 7.2 grams of o2 , how many grams of h2o can you produce ?

Which statement best describes the relationship between period and frequency of light waves? a) in wave b the period increases and the frequency decreases from wave a. b) in wave a the period increases and the frequency decreases from wave b. c) in wave b the period is shorter and the frequency is greater than in wave a. d) in wave a the period is shorter and the frequency is greater than in wave b.

An atom of lithium-7 has an equal number of(1) electrons and neutrons(2) electrons and protons(3) positrons and neutrons(4) positrons and protons