Question

7. Use the reaction enthalpies given below to determine AHºrxn for the following reaction: 8. Use the AHºf information provided to calculate AHºrxn for the following: P4(g) + 10 C12(g) + 4PC15(s) AHørxn = ? SO2Cl2(g) + 2 H2O(l) → 2 HCI(g) + H2804 Given: PC15(s) - PC13(g) + Cl2(g) P4(g) + 6 Cl2(g) - 4 PC13(g) AHørxn- +157 kJ Hºrxn=-1207 kJ AHºf (kJ/mol) SO2Cl2(g) H2O(1) HCl(g) H2S040) -364 -286 -92 -814 Voboty A) -2100. kJ B) -1835 kJ C) -1364 kJ D) -1050. kJ E) -1786 kJ A) -422 kJ B)-256 kJ C) +161 kJ D) -62 kJ E) +800. kJ

Answer 1

7)

Lets number the reaction as 0, 1, 2 from top to bottom

required reaction should be written in terms of other reaction

This is Hess Law

required reaction can be written as:

reaction 0 = -4 * (reaction 1) +1 * (reaction 2)

So, ΔHo rxn for required reaction will be:

ΔHo rxn = -4 * ΔHo rxn(reaction 1) +1 * ΔHo rxn(reaction 2)

= -4 * (157.0) +1 * (-1207.0)

= -1835 KJ

Answer: B

8)

Given:

Hof(SO2Cl2(g)) = -364.0 KJ/mol

Hof(H2O(l)) = -286.0 KJ/mol

Hof(HCl(g)) = -92.0 KJ/mol

Hof(H2SO4(l)) = -814.0 KJ/mol

Balanced chemical equation is:

SO2Cl2(g) + 2 H2O(l) ---> 2 HCl(g) + H2SO4(l)

ΔHo rxn = 2*Hof(HCl(g)) + 1*Hof(H2SO4(l)) - 1*Hof( SO2Cl2(g)) - 2*Hof(H2O(l))

ΔHo rxn = 2*(-92.0) + 1*(-814.0) - 1*(-364.0) - 2*(-286.0)

ΔHo rxn = -62 KJ

Answer: D