Calculate the net change in energy for the following reaction:
2na(s) + 2hcl(g) → 2nacl(s) + h2(g)
given the following information:
energy of sublimation of na(s) = 97 kj/mol
bond energy of hcl = 427 kj/mol
ionization energy of na(g) = 496 kj/mol
electron affinity of cl(g) = –349 kj/mol
lattice energy of nacl(s) = –778 kj/mol
bond energy of h2 = 432 kj/mol

-1078 kJ/mol.

Explanation:

Consider this reaction in three steps:

Sources of enthalpy changes in the first step:

That corresponds to an enthalpy change of

.

Sources of enthalpy changes in the second step:

That corresponds to an enthalpy change of

.

Sources of enthalpy changes in the third step:

That corresponds to an enthalpy change of

.

Take the sum of the enthalpy changes of the three steps to find the enthalpy change of the overall reaction:

.

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