Mothballs are composed primarily of naphthalene (C10H8). When 1.025 g of naphthalene burns in a bomb calorimeter, the temperature rises from 24.25 C to 32.33 C. (The Heat Capacity of the Calorimeter is 5.11 kJ/C.) Find DeltaE (in x 103 kJ) for the combustion of naphthalene.

-5.16 × 10³ kJ/mol

Explanation:

According to the law of conservation of energy, the sum of the heat released by the combustion of naphthalene (Qcomb) and the heat absorbed by the bomb calorimeter (Qcal) is zero.

Qcomb + Qcal = 0

Qcomb = -Qcal [1]

We can calculate the heat absorbed by the bomb calorimeter using the following expression:

Qcal = Ccal × ΔT

where,

Qcal = Ccal × ΔT = 5.11 kJ/°C × (32.33°C-24.25°C) = 41.3 kJ

From [1],

Qcomb = -41.3 kJ

41.3 kJ are released upon the combustion of 1.025 g of naphthalene (MW 128.17). The change in the internal energy (ΔE) is:

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answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e