How many molecules of dinitrogen pentoxide are contained 123.46g o dinitrogen

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?

Consider the following reactions. (note: (s) = solid, (l) = liquid, and (g) = gas.) mg(s) + ½o2(g) → mgo(s) + 146 kcal/mole h2(g) + ½o2(g) → h2o(g), δh = -57.82 kcal/mole what type of reaction is represented by the previous two examples?

If 16.00g of hydrogen gas reacts with 126.73g of oxygen, how many grams of water are yielded? (both reactants are completely consumed in the reaction.)