19. For the reaction 2 CO (g) + 2 NO (g) ® 2 CO 2(g) + N 2(g) , DH rxn = -746 kJ

Question

19. For the reaction 2 CO(g) + 2 NO(g) ® 2 CO2(g) + N2(g) , DHrxn = -746 kJ/mol. What is DH if 1.00 mol of CO2 reacts with a stoichiometrically appropriate amount of N2?

a. -746 kJ

b. +746 kJ

c. -373 kJ

d. +373 kJ

21. Calculate DH°rxn for CaCO3(s) + 2 HCl(g) ® CaCl2(s) + H2O(l) + CO2(g) given the following:

CaCO3(s) ® CaO(s) + CO2(g)                             DH°rxn = +175 kJ/mol

Ca(OH)2(s) ® H2O(l) + CaO(s)                         DH°rxn = +67 kJ/mol

Ca(OH)2(s) + 2 HCl(g) ® CaCl2(s) + 2 H2O(l)    DH°rxn = -198 kJ/mol

a. -90 kJ/mol

b. +44 kJ/mol

c. +90 kJ/mol

d. none of the above

22. 150.0 mL 0.200M HCl is mixed with 150.0 mL 0.200M NaOH in a coffee-cup calorimeter and react to form KBr and H2O (note that you are being given stoichiometrically-equivalent quantities). The solution temperature rises from 25.00°C to 27.10°C. What is DHrxn for HCl(aq) + NaOH(aq) ® NaCl(aq) + H2O(l)?

a. -2.633 kJ/mol

b. -13.17 kJ/mol

c. -87.77 kJ/mol

d. none of these

Explanation / Answer

19)

2 CO(g) + 2 NO(g) ® 2 CO2(g) + N2(g) , DHrxn = -746 kJ/mol

Lets reverse this reaction

2 CO2(g) + N2(g) ® 2 CO(g) + 2 NO(g) , DHrxn = 746 kJ/mol

In reaction when 2 mol of CO2, recats, DH = 746 KJ

So, for 1 mol of CO2, DH = 746 KJ / 2 = 373 KJ

Answer: d

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