Question

Heat Evolved During Combustion and Heat Capacity of a Gas at Constant Pressure

A.

Consider the following reaction:

2 C2H2(g) + 5 O2(g) 4 CO2(g) + 2H2O(l)

Use standard heats of formation from Zumdahl 'Chemical Principles' 8th ed. Appendix Four pp A19 - A21.

a) How much heat is evolved when 1.440×10¹ moles of C₂H₂(g) is burned in excess oxygen. Answer to 4 sig figs.

b) How much heat is evolved when 2.250×10² g of CO₂(g) is produced from the combustion of C₂H₂(g). Answer to 4 sig figs.

c) How much heat is evolved when 2.473×10² g of C₂H₂(g) is burned in excess oxygen. Answer to 4 sig figs.

B.

A system comprised of 1.567 moles of N₂O(g) cools from 190.0°C to 35.0°C at a constant pressure of 3.0 atm.
The molar heat capacity at constant pressure for N₂O(g) is 38.70 J K⁻¹ mol⁻¹.

a) Calculate q.

-9400 J

b) Calculate w.

2019 J

c) Calculate .

-7380 J

d) Calculate .

(cant figure this part out)

Answer 1

2C_2 H_4 (a) + SO_2 (a) rightarrow 4CO_2 (a) + 2H_2O (l) delta H_r times w = [4 times OH^dot_f CO_2 + 2 times OH^dot_f H_2O] - [2 times OH^dot_f C_2 H_2 + 5 times OH^dot_f O_2] = [(4 times -393.51) + 2 times (-285.83)] - [2 times 226.73 + 5 times 0.0] = -1574.04 - 571.66 - 453.46 delta H_r times w = -2599.16 KJ A/C to calculation 2 moles of C_2 H_2 using to produce = -2599.16 KJ 1.440 times 10 moles of C_2 H_2 busing to produce = ? -2599.16 times 1.44 times 10^1/2 = -18713.952 KJ Amount of energy produced = 187.1 times 10^2 KJ Mass of CO_2 = 2.250 times 10^2 g moles mass of CO_2 = 44g No. of moles of CO_2 = 2.250 times 10^2/44 = 5.1136 moles A/C to eq 4 mo9les of CO_2 = 2599.16 KJ 5.1136 moles of CO_2 = ? 2599.16 times 5.1136/4