How many moles of XeO2 are in 67.9 grams

Can you guys me with question no. 5!

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

To find the enthalpy of a reaction in the lab, you measured the of the reactants and the change during the reaction.