What instrument is used to determine the heating value of coal?

The instrument used to determine the heating value of coal is a calorimeter. A calorimeter is specifically designed to measure the heat energy released during a combustion reaction. In the context of coal, this typically involves burning a sample of coal within the calorimeter and measuring the heat produced. The resulting data allows engineers and researchers to calculate the coal's heating value, which is essential for assessing its efficiency and effectiveness as a fuel source.

In contrast, a thermometer measures temperature, but it does not provide information about the heating value of materials. A barometer primarily measures atmospheric pressure and has no relevance to heating values. A manometer, which measures the pressure of gases or liquids, is also not applicable for determining the calorific values of fuels. Thus, the calorimeter is the only instrument among the choices that is specifically suited to the task of measuring the heating value of coal.