What has the lowest atomic mass in period 5

What type of reaction is zn + cucl2 → cu + zncl2?

According to the vsepr theory what is the shape of a molecule that has a central atom valence three other items with no lone pairs of electrons

Ammonium perchlorate nh4clo4 is the solid rocket fuel used by the u.s. space shuttle. it reacts with itself to produce nitrogen gas n2 , chlorine gas cl2 , oxygen gas o2 , water h2o , and a great deal of energy. what mass of nitrogen gas is produced by the reaction of 2.1g of ammonium perchlorate?