Which of the following equations violates the law of conservation of mass?

a) 2al + 6hcl yields 2alcl3 + 3h2
b) na2c2o4 + pb(no3)2 yields pbc2o4 + 2nano3
c) agno3 + licl yields agcl + lino3
d) 3ca + 2cr(no3)3 yields 3ca(no3)3 + 2cr

A4.86 g piece of metal was placed in a graduated cylinder containing 15.5 ml of water. the water level rose to 17.3 ml. what is the density of the metal. i need the steps of how to solve it to so i can use a formula to work out other problems.