Question

For which of the following reactions is ΔH∘rxn equal to ΔH∘f of the product(s)?

You do not need to look up any values to answer this question.

Check all that apply.

Hints

Check all that apply.

H2(g)+12O2(g)→H2O(g)

Na(s)+12Cl2(g)→NaCl(s)

2Na(s)+Cl2(g)→2NaCl(s)

H2O2(g)→12O2(g)+H2O(g)

Na(s)+12Cl2(l)→NaCl(s)

2H2(g)+O2(g)→2H2O(g)

Answer 1

in order to have Hf:

- Reactatnts must be in Elemental states

- Most stable allotropes

- STP conditions

- 1 mol of product must be formed

H2(g)+12O2(g)→H2O(g) --> correct, since 1 mol of product is formed form most stable allotropes

Na(s)+12Cl2(g)→NaCl(s) --> correct, since 1 mol of product is formed form most stable allotropes

2Na(s)+Cl2(g)→2NaCl(s) --> False, 2 mol of products are formed, we need only 1

H2O2(g)→12O2(g)+H2O(g) --> false, it must be formed from pure elements - REACTANTS

Na(s)+12Cl2(l)→NaCl(s) --> false, Cl2 is not liquid at STP

2H2(g)+O2(g)→2H2O(g) --> False, 2 mol of products are formed, we need only 1