Zinc nitrate and calcium nitrate solution can be distinguished by reaction with ammonium hydroxide. Zinc forms a white gelatinous ppt. whereas there is no precipitation of calcium hydroxide even with excess of ammonium hydroxide
Some chemical reactions show release of heat while some show absorption of heat. On these bases, the reaction is classified as either endothermic or exothermic. Negative sign of ΔH means exothermic reaction.