Lab Report On Enthalpy Change

The purpose of this lab is to figure out the mass percentage of copper in a penny. Furthermore, by doing this lab we will practice using a spectrophotometer and review the names of equipment such as volumetric glassware, pipets, and volumetric flasks.

The main objective of this experiment is to differentiate between a physical change and a chemical change.

This information has massively help to answer by explain the difference between endothermic and exothermic in common language which also helped me know why an exothermic reaction can be used to heat food but an endothermic reaction cannot.

In order to measure the heats of reactions, add the reactants into the calorimeter and measure the difference between the initial and final temperature. The temperature difference helps us calculate the heat released or absorbed by the reaction. The equation for calorimetry is q=mc(ΔT). ΔT is the temperature change, m is the mass, c is the specific heat capacity of the solution, and q is the heat transfer. Given that the experiment is operated under constant pressure in the lab, the temperature change is due to the enthalpy of the reaction, therefore the heat of the reaction can be calculated.

This reaction is exothermic, meaning it releases heat when reactants are converted into products. The negative change in enthalpy (∆H° = -36,757 J) for this reaction indicates that the reaction is losing heat to its surroundings.

Examine a piece of nichrome wire. On the data sheet, record the color and the luster of the metal. Use a forceps to hold the wire in the flame of your burner for about two minutes (recall where the hottest part of the flame is located). Describe the appearance of the wire while held in the hottest part of the flame. Allow the wire to cool and reexamine it. From your observations, determine if there was a physical or a chemical change. Give specific reasons for your conclusions. Save the nichrome wire for step #2.

The first trial that contained 10 mL of NaOH and 10 mL of CH3COOH produced a ΔHrxn of -13.11 kJ/m. The second trial, which contained 15 mL of NaOH and 5 mL of CH3COOH resulted in a ΔHrxn of -7.864 kJ/m. Based on the literature value of NaOH CH3COOH, -57.5 kJ/m, we were off by 44.39 kJ/m in the first trial, and 49.64 kJ/m in the second trial.

Enthalpy (H)- The sum of the internal energy and the pressure – volume product of a system H= E + PV.

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Endothermic and Exothermic reactions release or absorb energy, the graph above shows the way in which the chemical energy changes.

The literature value for the enthalpy change of the last reaction which was provided by our teacher is -97 kJ mol-1. Agreeing this value, our result can be considered accurate.

We will be using 6 different fuels to heat up 100ml of water, and find out the changes of the temperature. We will measure the temperatures of the water before and after the experiment. We will burn heat the water for exactly 2 minutes, and check the changes in temperature. The change in temperature will allow us to work out the energy given off the fuel by using this formula:

Introduction: The theory behind this experiment is the heat of a reaction (∆E) plus the work (W) done by a reaction is equal to

Purpose: To measure the heats of reaction for three related exothermic reactions and to verify Hess’s Law of Heat Summation.

Introduction: Every chemical change is accompanied by a change in energy usually in the form of heat. If heat is evolved, the reaction is exothermic, and if heat is absorbed, the reaction is endothermic. The energy change of a reaction that occurs at constant pressure is called the heat of reaction or the enthalpy of reaction (ΔHr). This quantity of heat is measured experimentally by allowing the reaction to occur in a calorimeter. In this experiment you will determine the heat of neutralization when an acid and a base react to form 1 mole of water. In a perfect calorimeter, heat is exchanged only between the reaction and the calorimeters water. Technically, some heat may may be absorbed the calorimeter. All calorimeters exchange some heat with its environment. This amount of heat is called the calorimeters heat capacity (the amount of of heat required to raise its temperature 1∘Celsius). We are going to “pretend” that our calorimeter is the perfect calorimeter.