What is enthalpy in simple words? Answering this question is the objective of today’s post. Remember, in the previous post, we talked about internal energy and how it can change by either heat or work. Rearranging this equation … Read more
The terms endothermic and exothermic are used to describe the heat transfer during different processes including chemical reactions. In general, the focus in this chapter is going to be on heat transfer because thermochemistry is the study of heat change … Read more
Having a library of values for standard enthalpies of formation allows calculating the enthalpy of reaction without doing calorimetric analysis. There are two approaches to doing this. 1) The Direct Approach If the enthalpies of formations for all the components … Read more
In the previous post that a calorimeter is a device for measuring the heat flow, and for reactions under constant pressure, the calorimeter measures the enthalpy of the reaction (ΔH). Now, a bomb calorimeter is an equipment that measures ΔE … Read more
A calorimeter is a device for measuring heat flow. One application of calorimetry is measuring the enthalpy of a reaction. So, how does heat become enthalpy? Remember, the formula for enthalpy change is: ΔH = ΔE + ΔPV … Read more
In the previous post, we talked about heat capacity, specific heat, and the formula for the relationship between these and the change in temperature. Below are some additional practice examples of heat capacity problems. When solving a problem … Read more
In the previous post, we talked about the Hess’s law and how it can be used for measuring the enthalpy change (ΔH) for a reaction without making calorimetric measurements. In short, the Hess’s law is based on the fact that enthalpy is … Read more
In this set of practice questions, we will summarize the main concepts of thermochemistry such as the relationship between internal energy, work and heat, exothermic and endothermic process, heat capacity, constant pressure calorimetry, constant-volume calorimetry, the enthalpy, the standard enthalpies … Read more
Hess’s law allows measuring the enthalpy change (ΔH) for a reaction without making calorimetric measurements. To do this, we need the enthalpies of some other reactions. For example, Using the given data for reactions (1) and (2), calculate the ΔH for … Read more
Standard enthalpy of formation (or heat of formation), ΔHof , is the enthalpy change when 1 mol of the substance is formed from its constituent elements in their standard states. For example, the formation of 1 mol ammonia from H2 … Read more
