Answer:
Compound are substances which can be formed by chemically combining two or more elements. Mixtures are substances that are formed by physically mixing two or more substances. Compounds can be of three types, which are: covalent compounds, metallic compounds and ionic compounds.
A.) 3 H2SO4 + 2 Al > Al2(SO4)3 + 3 H2
6 H+ +3 S +12 O +2 Al> 2 Al + 3S + 12O + 6H+
This one is balanced, with 6 H, 3 S, 12 O, and 2 Al on both sides.
B.) 2KCl + Pb(NO3)2 > KNO3 + PbCl2
2K + 2Cl + Pb + 2N +6 O > 1 K + 1 N+ 3 O + Pb + 2 Cl
This one is not balanced as there is 2 K, 6 O and 2 N on the reactants side but only 1 K, 3 O, and 1 N on the products side.
Therefore, only A.) is balanced
THe addition of strong electrolyte such as MgSO4 compound will led the equilibrium to shift due to common ion effect. The addition of common ion decrease the solubility as the reaction shift to the left thus less product is formed.