A calorimeter constant (denoted ''C''_cal) is a constant that quantifies the

heat capacity Heat capacity or thermal capacity is a physical property of matter, defined as the amount of heat to be supplied to an object to produce a unit change in its temperature. The SI unit of heat capacity is joule per kelvin (J/K). Heat capacity is a ...

of a

calorimeter A calorimeter is a device used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal micro calorimeters, titration calorimeters ...

. It may be calculated by applying a known amount of

heat In thermodynamics, heat is energy in transfer between a thermodynamic system and its surroundings by such mechanisms as thermal conduction, electromagnetic radiation, and friction, which are microscopic in nature, involving sub-atomic, ato ...

to the calorimeter and measuring the calorimeter's corresponding change in

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

. In SI units, the calorimeter constant is then calculated by dividing the change in

enthalpy Enthalpy () is the sum of a thermodynamic system's internal energy and the product of its pressure and volume. It is a state function in thermodynamics used in many measurements in chemical, biological, and physical systems at a constant extern ...

(Δ''H'') in

joule The joule ( , or ; symbol: J) is the unit of energy in the International System of Units (SI). In terms of SI base units, one joule corresponds to one kilogram- metre squared per second squared One joule is equal to the amount of work d ...

s by the change in temperature (Δ''T'') in

kelvin The kelvin (symbol: K) is the base unit for temperature in the International System of Units (SI). The Kelvin scale is an absolute temperature scale that starts at the lowest possible temperature (absolute zero), taken to be 0 K. By de ...

s or degrees Celsius: :

C_\mathrm = \frac

The calorimeter constant is usually presented in units of joules per degree Celsius (J/°C) or joules per kelvin (J/K). Every calorimeter has a unique calorimeter constant.

Uses

The calorimeter constants are used in constant pressure calorimetry to calculate the amount of heat required to achieve a certain raise in the temperature of the calorimeter's contents.

Example

To determine the change in

in a neutralization reaction (Δ''H''_{neutralization}), a known amount of basic solution may be placed in a calorimeter, and the temperature of this solution alone recorded. Then, a known amount of acidic solution may be added and the change in temperature measured using a

thermometer A thermometer is a device that measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb ...

. The difference in temperature (Δ''T'', in units K or °C) may be calculated by subtracting the initial temperature from the final temperature. The enthalpy of neutralization Δ''H''_{neutralization} may then be calculated according to the following equation: :

\Delta = C_\mathrm \cdot \Delta

. Regardless of the specific

chemical process In a scientific sense, a chemical process is a method or means of somehow changing one or more chemicals or chemical compounds. Such a chemical process can occur by itself or be caused by an outside force, and involves a chemical reaction of som ...

, with a known calorimeter constant and a known change in temperature the heat added to the system may be calculated by multiplying the calorimeter constant by that change in temperature.

References

{{reflist Calorimetry Thermochemistry

Uses

Example

See also

References