Question

4a) Estimate ΔHrxn for the following chemical reaction using the bond enthalpies in the table found here. Report your answer to zero decimal places in standard notation (i.e. 123. kJ *For numbers ending in zero, be sure to include the decimal!*).

N2H4(g) + O2(g) → N2(g) + 2H2O(g)

b) Without doing any calculations, predict the sign of ΔSsys for each of the following processes:

(positive or negative) The decomposition of Na2CO3 into its constituent elements

(positive or negative) CH4(g) + H2O(l) → CO(g) + 3H2(g)

(positive or negative) PBr3(g) + 3H2O(l) → 1H3PO3(l) + 3HBr(g)

(positive or negative) The freezing of C4H8O2

c) Using the standard entropies below, calculate ΔS°rx (in J/K) for the following reaction.

Report your answer to two decimal places in standard notation (i.e. 123.45 J/K).

2H2O(l) + 2F2(g) → 4HF(g) + O2(g)

Compound		S° (J mol-1 K-1)
H2O (l)		69.91
F2 (g)		202.80
HF (g)		173.78
O2 (g)		205.70

Answer 1