Question

Choose the reaction that illustrates delta ΔH °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) + 3O₂ (g)

Answer 1

The correct choice that illustrates delta ΔH °f for Ca(NO₃)₂ is option d) Ca(NO₃)₂ (aq) → Ca²⁺ (aq) + 2NO₃⁻ (aq).

Step-by-step explanation:

The correct choice that illustrates delta ΔH °f for Ca(NO₃)₂ is option d) Ca(NO₃)₂ (aq) → Ca²⁺ (aq) + 2NO₃⁻ (aq).

This reaction represents the formation of Ca(NO₃)₂ from its elements in their standard states. The enthalpy change, ΔH °f, is the standard enthalpy of formation and is defined as the enthalpy change when one mole of a compound is formed from its elements in their standard states at a constant pressure of 1 bar and a specified temperature (usually 298 K).

In this reaction, one mole of Ca(NO₃)₂ is formed from its elements, which are Ca²⁺ (aq) and 2NO₃⁻ (aq). The enthalpy change, ΔH °f, for this reaction is a measure of the energy released or absorbed during the formation of one mole of Ca(NO₃)₂ from its elements.