Enthalpy Changes

Multiple Choice

A student carried out an experiment to determine the enthalpy change for the combustion of ethanol. The following results were obtained by the student. How much of the heat energy produced by the burning of ethanol went to the water?

• 100 X 4.18 X 20 J

• 150 X 4.18 X 20 J

• 0.57 X 4.18 X 20 J

• 100 X 4.18 X 41 J

Multiple Choice

1.20 g of ethanol is combusted releasing 35500 J of energy. What is the molar enthalpy change for the combustion of ethanol?

$$\Delta H\ =\ \frac{q}{n}$$

• A

• B

• C

• D

Multiple Choice

A student mixed 30.0 cm³ of 0.0250 mol dm^-3 KOH solution with 30.0 cm³ of 0.0250 mol dm^-3 HNO₃. The temperature rose by 0.5 °C. Assume no heat was lost in the surroundings. What is the molar enthalpy change for the reaction?

Multiple Choice

An iron block with a mass of 0.11 kg absorbs 504 J of heat energy. What is the temperature rise in K?

Specific heat capacity of iron = 0.448 J g^-1 K^-1

$$\Delta T\ =\ \frac{q}{mc}$$

• 1.02 X 10⁴

• 1.10

• 10.23

• 9.78 X 10^-2

Multiple Choice

In a calorimetric experiment 2.5 g of a fuel is burnt in oxygen. 30% of the energy released during combustion is absorbed by 500 g of water, the temperature which rises from 25°C to 68°C. The specific heat capacity of water is 4.2 J g^-1 K^-1.

What is the total energy released per gram of fuel burnt?

Multiple Choice

The reaction of HCl with NaOH produced an overall temperature increase of 24.4 K.

Given the following data, how much thermal energy was evolved during this reaction?

Initial Temperature of 25.0 cm³ HCl = 17.6

Initial Temperature of 25.0 cm³ NaOH = 18.5

Specific Heat Capacity of Water = 4.18 J g^-1 K_-1

$$q\ =\ mc\Delta T$$