Now that we have put a coefficient of 3 in front of caso4, what coefficient should go in front of cacl2 to balance calcium (ca)? 3caso4+alcl3→? cacl2+al2(so4)3

3

The law of conservation of mass state that the mass of product would be the same as the mass of the reactant. If there is X amount of calcium used in reactant, there should be X amount of calcium in the product.

The coefficient of the CaSO4 is 3. CaSO4 compound should have 1 calcium element for each compound. CaCl2 compound has 1 calcium element for each compound. So the coefficient should be:
CaSO4/CaCl2 = 1/1
CaCl2 = CaSO4* 1/1
CaCl2 = 3

Ithink it’s 3 as the answer.