Question

choose the reaction that illustrates delta H *f for Ca(NO3)2.(A) Ca (s) + N2 (g) + 3O2 ---> Ca(NO3)2 (s)(B) Ca2 (aq) + 2 NO3- (aq) ---> Ca(NO3)2 (aq)(C) Ca (s) + 2N (g) + 6O (g) ---> Ca(NO3)2 (s)(D) Ca(NO3)2 (aq) ---> Ca2+ (aq) + 2NO3- (aq)(E) Ca(NO3)2 (s) ---> Ca(s) + N2 (g) + 3 O2 (g)

Answer 1

Answer: The correct answer is Option A.

Explanation:

Standard enthalpy of formation is the change in enthalpy of  one mole of a substance present at the standard state that is 1 atm of pressure and 298 K of temperature. The substance is formed from its pure elements under the same conditions.

We are given a chemical compound having chemical formula $Ca(NO_3)_2$

This compound is formed by the combination of calcium, nitrogen and oxygen elements.

The chemical equation for the formation of $Ca(NO_3)_2$ from the components in their standard states follows:

$Ca+N_2+3O_2\rightarrow Ca(NO_3)_3$

Hence, the correct answer is Option A.