1. Heat of combustion

Aim: To determine the heat of combustion of ethanol.

Requirements: Ethanol, Thin-walled can, thermometer, 100cm³ of water, wind shield, spirit lamp, chemical balance, clamp and stand.

Procedure:-

• Use the measuring cylinder to measure exactly 100cm3 of water and pour it into the clamped thin-walled can. Note the initial temperature.
• The spirit lamp is half filled with ethanol and tightly closed since it is highly volatile. The spirit lamp with ethanol is weighed and its mass taken. It is lit and immediately placed under the metal can such that much of the flame is in contact with the can. The flame is shielded from air currents using the wind shield. Stir the water with the thermometer to ensure that the heat is uniformly. Distributed while observing the temperature rise.
• When there is a reasonable rise in temperature of about 20° C, the final temperature is taken and the flame immediately put off. The alcohol burner and content is then reweighed and its final mass recorded

2. Heat of Neutralization

Aim: To measure the heat of neutralization of hydrochloric acid by sodium hydroxide.

Theory: Hydrochloric acid reacts with sodium hydroxide to evolve heat. It is this heat that is used to raise the temperature of the thermometer.

Procedure

• 100cm³ of molar hydrochloric acid is measured using a clean measuring cylinder and poured into a clean well-lagged polythene cup placed in an empty beaker.
• The temperature of the molar hydrochloric acid is recorded. The measuring cylinder and the thermometer are rinsed with distilled water and then with aqueous sodium hydroxide, 100cm³ of molar sodium hydroxide is measured with a measuring cylinder, its temperature taken and recorded and then quickly transferred into the hydrochloric acid in the polythene cup. The mixture is stirred gently with the thermometer taking the highest temperature of the mixture.