problems involving heat flow and temperature changes

It has been seen that energy change occurring during the reaction at constant temperature and constant volume is given by internal energy change. However, most of the reactions in the laboratory are carried out in open beakers or test tubes, etc. In such cases, the rea..

When we heat a solid, we add energy to the system increasing the vibration of the particles. Eventually these particles break free from their binding forces and melt. The normal melting point of a crystal is the temperature at which it melts under one atmospheric pressure. Incre..

R is the internal energy of the reactants. If the internal energy of the products is less than the internal energy of the reactants, the D E would be negative. On the other hand, when the internal energy of the products is more than the internal energy of the reactants, then D E would be positi..

Gibbs Free Energy Change and Work - We have learnt that of D G is a measure of the spontaneity of a chemical reaction. It can be shown that the free energy of a process is equal to maximum possible work that can be derived from the process as given below: From first law of thermodynamics,..

A liquid may be made to boil at any desired temperature by changing the external pressure. For example, a liquid may be made to boil at higher temperature by increasing the pressure on its surface, as is done in a pressure cooker. It may be made to boil at a lower ..

The criterion for a chemical change is the production of one or more new substances. Therefore, certain conditions should be met in order to bring about a chemical change. The necessary conditions are: 1) A minimum amount of energy needed to initiate a reaction, called the activ..

Calorimetry is the measurement of the amount of heat evolved or absorbed in a chemical reaction, change of state, or formation of a solution. We know that heat flows from a hot substance to a cold substance. In Calorimetry, a hot substance and a cold substanc..

> The quantity dT/dx, is called the temperature gradient. The minus sign indicates that dT/dx is negative along the direction of the heat flow. The unit of thermal conductivity can be easily worked out using equation (1) or equation (2). The SI unit is Js -1 m -1 K -1 ..

In a physical change the shape, size, appearance or state of a substance may alter, but it is a temporary change, which is usually reversible. There is no new substance formed, no change in the mass of the substance and no energy changes are involved..

Measurement of Enthalpy of Reactions - The heat changes in chemical reactions are measured with the help of calorimeters. Depending upon the requirements of experiments different types of calorimeters are used. In general, reactions taking place at constant volume and invol..