Question

QUESTION 4 The combustion reaction for octane burning in oxygen is: 2 C8H18 ()25 O2(g)- 16 CO2(g) +18 H20(g) AH = -10869 kJ Suppose an oxygen bomb calorimeter is loaded with oxygen gas and excess octane. The oxygen gas has a volume of 480.0 mL, pressure of 8.28 atm, and an initial temperature of 22.1 °C The calorimeter has a heat capacity of 1.75 kJ/ °C Assuming the oxygen reacts completely, what is the final temperature of the calorimeter?

Answer 1

1st calculate mol of O2 reacting.

Given:

P = 8.28 atm

V = 480.0 mL

= (480.0/1000) L

= 0.48 L

T = 22.1 oC

= (22.1+273) K

= 295.1 K

find number of moles using:

P * V = n*R*T

8.28 atm * 0.48 L = n * 0.08206 atm.L/mol.K * 295.1 K

n = 0.1641 mol

From reaction,

Heat produced by 25 mol of O2 = 10869 KJ

So,

Heat produced by 0.1641 mol of O2 = 10869* 0.1641/25 = 71.344 KJ

Now use:

Q = Ccal * (Tf-Ti)

71.344 KJ = 1.75 KJ/oC * (Tf - 22.1)

Tf - 22.1 = 40.8

Tf = 62.9 oC

Answer: 62.9 oC