Which information can be determined using half life

Nitrogen dioxide reacts with water to form nitric acid and nitrogen monoxide according to the equation: 3no2(g)+h2o(l)→2hno3(l)+no(g) part a suppose that 4.2 mol no2 and 0.50 mol h2o combine and react completely. which reactant is in excess? express your answer as a chemical formula. nothing

If the atomic mass of an atom is 34 and the atom contains 13 protons, how many neutrons does the atom contain?

Calculate - analysis of compound composed of iron and oxygen yields 174.86 of fe and 75.14g of o. what is the empirical formula for this compound?