What happens to the total mass of a substance undergoing a physical change

Calculate the change in entropy if br2(l) is converted into gaseous br atoms. s° for br2(l) = 152.2 j/(mol•k) s° for br2(g) = 245.5 j/(mol•k) s° for br(g) = 175.0 j/(mol•k)

1.aluminum chloride (alcl3), and sodium hydroxide (naoh) can react to form aluminum hydroxide (al(oh)3) and sodium chloride (nacl).    you have 13.4 g of aluminum chloride and 10.0 g of sodium hydroxide. answer the following questions: •what is the balanced equation for this reaction? •if you use all 13.4 g of aluminum chloride, how many grams of aluminum hydroxide can be formed? work must be shown to earn credit •if you use all 10.0 g of sodium hydroxide, how many grams of aluminum hydroxide can be formed? work must be shown to earn credit •how many grams of aluminum hydroxide will actually be made?     which reagent is limiting? explain your answer.

Acompound contains c, h, and o atoms. when 1.130 g of the compound is burned in oxygen, 1.064 g co2 and 0.3631 g h2o are produced. what is the empirical formula of this compound?