Can someone help me with these 2 questions

Sulfuric acid (a component of acid rain) reacts with limestone (calcium carbonate) to produce calcium sulfate and carbon dioxide. this damages buildings and statues made of limestone. which solution of sulfuric acid will damage these structures more quickly? a. 0.001% b. 0.005% c. 0.010% d. 0.015%

Summarize possible ways in which phases of matter could combine to form a solution.

What is the value of the standard enthalpy of formation of an element in its most stable form?