Question

Which of these statements are true? Select all that apply.

The Delta.Hf for Br2(I) is 0 kJ/mol.

The Delta.Hf for He(I) is 0 kJ/mol.

The Delta.Hf for Hg(I) is 0 kJ/mol.

The Delta.Hf for Cl2(g) is 0 kJ/mol.

The Delta.Hf for N2(I) is 0 kJ/mol.

Answer 1

Delta Hf° = 0 for an element in its most stable form at standard conditions (1 bar, 25 °C).

Interpreting "I" as the letter l (liquid), the true statements are:
- Br2(l) — TRUE (bromine's standard state is liquid)
- Hg(l) — TRUE (mercury is liquid)
- Cl2(g) — TRUE (chlorine is a gas)

The false ones:
- He(l) — FALSE (helium's standard state is He(g), not liquid)
- N2(l) — FALSE (nitrogen's standard state is N2(g), not liquid)

If instead "I" was intended to mean gas, then He(g) and N2(g) would be TRUE.