Predict whether the following reactions will be exothermic or endothermic

a) n2(g)+ 3h2(g) --> 2nh3(g)
b) s(g) +o2(g) > so2(g)
c) 2h2o(g) > 2h2(g) + o2(g)
d) 2f(g) +f2(g)

bond
h-h 432 kj/mol
n-n(triple bond) 942 kj/mol
o=o 494 kj/mol
f-f 155 kj/mol
h-n 386 kj/mol
h-o 459 kj/mol
s=o 522 kj/mol

A) N2(g)+ 3H2(g) --> 2NH3(g)    exothermic

B) S(g) +O2(g) ---> SO2(g)    endothermic

C) 2H2O(g) >2H2(g) + O2(g)    endothermic

D) 2F(g) +F2(g)   endothermic

Explanation:

Hello,

By computing the energy difference between the products and reagents for each chemical reaction, one obtains:

A) N2(g)+ 3H2(g) --> 2NH3(g)

ΔrH=2*386 kJ/mol-942 kJ/mol-3*432 kJ/mol=-1466kJ/mol->exothermic

B) S(g) +O2(g) ---> SO2(g)

ΔrH=522 kJ/mol-494 kJ/mol=28kJ/mol->endothermic

C) 2H2O(g) >2H2(g) + O2(g)

ΔrH=2*432 kJ/mol+494 kJ/mol-2*459 kJ/mol=440kJ/mol->endothermic

D) 2F(g) --->F2(g)

ΔrH=155kJ/mol>endothermic

Best regards.