Question

determining enthalpy of formation which of these statements are true? choose three correct answers the δhf for cl2 (g) is 0 kj/mol. the δhf for he (l) is 0 kj/mol. the δhf for br2 (l) is 0 kj/mol. the δhf for hg (l) is 0 kj/mol. the δhf for n2 (l) is 0 kj/mol.

Explanation:

The standard enthalpy of formation ($\Delta H_f$) of an element in its standard state is 0 kJ/mol. Chlorine's standard state is $Cl_2(g)$, bromine's is $Br_2(l)$ and mercury's is $Hg(l)$. Helium's standard state is $He(g)$ and nitrogen's is $N_2(g)$. So, statements about $Cl_2(g)$, $Br_2(l)$ and $Hg(l)$ having $\Delta H_f = 0$ kJ/mol are correct based on the definition of standard - state elements.

Answer:

The $\Delta H_f$ for $Cl_2(g)$ is 0 kJ/mol, The $\Delta H_f$ for $Br_2(l)$ is 0 kJ/mol, The $\Delta H_f$ for $Hg(l)$ is 0 kJ/mol.