For the reaction 2H2 + O2 - 2H2O, if 30.0 g of H2 is reacted with 20.0 g of O2 what mass of the excess reagent is left over? ​

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

Solutions of sodium carbonate and silver nitrate react to form solid silver carbonate and a solution of sodium nitrate. a solution containing 3.50 g of sodium carbonate is mixed with one containing 5.00 g of silver nitrate. how many grams of sodium carbonate, silver nitrate, silver carbonate, and sodium nitrate are present after the reaction is complete?

Word equation for k(s)+h2o(l) yield koh(aq) + h2(g)