Question

Which of the following is the formation reaction for Na2CO3 (s)? A. 4 Na(s) + 2 C(s, graphite) + 3 O2(g) → 2 Na2CO3(s) B. 2 Na(s) + C(s, graphite) + 3 O(g) → Na2CO3(s) C. 2 Na(g) + C(g) + 1.5 O2(g) → Na2CO3(s) D. 2 Na(s) + C(s, graphite) + 1.5 O2(g) → Na2CO3(s) E. Na2(s) + C(s, graphite) + 1.5 O2(g) → Na2CO3(s)

Answer 1

Heat of formation reaction:

- Must produce only 1 mol of Na2CO3(s)

- Must be formed from elements, i.e. Na, C, O only

- Must be pure elements, no compounds

- Must be in elemental state, i.e. STP and abundant allotrope

then:

A. 4 Na(s) + 2 C(s, graphite) + 3 O2(g) → 2 Na2CO3(s)

can't be since 2 mol of NA2CO3

B. 2 Na(s) + C(s, graphite) + 3 O(g) → Na2CO3(s)

can't be since O(g) is not found in nature, but O2(g) does

C. 2 Na(g) + C(g) + 1.5 O2(g) → Na2CO3(s)

metal Na is not likely to be found as a gas

D. 2 Na(s) + C(s, graphite) + 1.5 O2(g) → Na2CO3(s)

this is the best fit

E. Na2(s) + C(s, graphite) + 1.5 O2(g) → Na2CO3(s)

can't be, since Na2(s) is not likely to appear