Abomb calorimeter has a heat capacity of 2.47 kj/k. when a 0.105-g sample of ethylene (c2h4) was burned in this calorimeter, the temperature increased by 2.14 k. calculate the energy of combustion for one mole of ethylene. a. –1.41 × 103 kj/mol b. –660 kj/mol c. –5.29 kj/mol d. –0.259 kj/mol e. –50.3 kj/mol

A. –1.41 × 10³ kJ/mol

Explanation:

According to the law of conservation of energy, the sum of the heat released by the combustion and the heat absorbed by the calorimeter is zero.

Qcal + Qcomb = 0

Qcomb = -Qcal  [1]

We can calculate the heat absorbed by the calorimeter using the following equation:

Qcal = Ccal × ΔT

where,

Ccal is the heat capacity

ΔT is the change in the temperature

From [1]

Qcomb = -Qcal = -Ccal × ΔT = -2.47 kJ/K × 2.14 K = -5.29 kJ

We know that the molar mass of ethylene is 28.05 g/mol. Then, the heat released per mole of ethylene is:

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.