Calorimetry

Date Performed: November 15, 2012

Calorimetry

M.J.M. VINUYA AND Z. LORENZO

INSTITUTE OF CHEMISTRY, COLLEGE OF SCIENCE

UNIVERSITY OF THE PHILIPPINES, DILIMAN, QUEZON CITY, PHILIPPINES

RECEIVED NOVEMBER 20, 2012

INTRODUCTION

HEAT IS DEFINED AS THE ENERGY TRANSFERRED BETWEEN A SYSTEM AND ITS SURROUNDING AS A RESULT OF TEMPERATURE DIFFERENCES.

Physical and chemical processes are usually accompanied by changes in temperature where heat may be generated or absorbed. The amount of heat exchanged by the system and the surrounding at constant temperature is called the heat of reaction (qrxn). When measured at constant pressure, the heat absorbed or evolved is equal to the enthalpy change (ΔH).

One common type of this reaction is combustion reaction where heat is released by the reaction. The said process is called exothermic reaction where heat is released, thus, giving a negative ΔH. If the reaction absorbs heat, it is known to be an endothermic reaction, giving a positive ΔH.

The ΔH of the reaction can be calculated by using the following formula:

ΔHrxn = Hf - Hi [1]

Where the enthalpy change of the reaction is the difference between the enthalpy of the final state (Hf) and enthalpy of the initial state (Hi).

The process of measuring the enthalpy change (ΔH) is called calorimetry. The said process is also done to measure the heats of reaction experimentally by using a device called calorimeter.

The system involved in this experiment us an isolated system since the calorimeter is preventing the exchange of heat (and matter) between the system and the surroundings. Hence, the heat exchanges is only limited to the reaction components and the calorimeter. Since there is no exchange of heat between the system and surroundings, the heat change of the system is zero.

qsystem = qreaction + qcal = 0 [2]

When a reaction occurs, the chemical energy is converted to thermal energy, making the temperature...