Question

In need of a numbered, styrofoam cup calorimetry laboratory procedure. This experiment will utilize redox chemical process.

Basic materials include:

Styrofoam cups

Digital thermometers

Cardboard

3M HCL, H2SO4, C2H4O2, NAOH, NH4Cl

Mg, Al, Zn, Fe, Cu

Answer 1

Some of the measurements you need to make in this experiment require additional steps not necessarily described in this handout. Use what you learned from previous labs to proceed correctly.

The calorimeter you will use in this experiment looks similar to the figure below:

Thermometer

Cardboard top

Two stacked

styrofoam cups

On the report sheet, fill the information requested by following the steps below.

Part A: Heat of solvation of calcium chloride (CaCl₂)

1. Place about 50 mL of water into the coffee cup calorimeter. You need to record the exact mass of the water. Describe on the report sheet how you determined the mass of the water.

2. Record the temperature of the water in ?C. Make sure the temperature stays constant over a few minutes; if not, take an average temperature.

3. Measure between 1.5 and 2 grams of CaCl₂ and record the exact mass. Describe on the report sheet how you determined the mass of the calcium chloride.

4. Add all the CaCl₂ to the calorimeter, cover with the lid, quickly swirl the solution to mix and observe the temperature. Record the highest temperature reached.

5. Calculate the amount of heat received or lost by the solution using the formula given on the first page. The mass of the solution is the mass of the water plus the mass of the calcium chloride. The specific heat of the solution is assumed to be the same as that of water.

6. Is the solvation of calcium chloride exothermic or endothermic?

7. Calculate the moles of calcium chloride by dividing the mass of our sample by the molar mass of calcium chloride.

8. Calculate the heat of solvation of calcium chloride by dividing the amount of heat obtained above by the number of moles of calcium chloride.

Part B: Heat of Neutralization

1. Place exactly 50.0 mL of 1.00 M NaOH into the coffee cup calorimeter. Describe on the report sheet how you determined the volume of NaOH.

2. Record the temperature of the solution in ?C. Make sure the temperature stays constant over a few minutes; if not, take an average temperature.

3. Place exactly 50.0 mL of 1.00 M HCl into a beaker. Describe on the report sheet how you determined the volume of HCl.

4. Wipe off the thermometer and measure the temperature of the 1.00 M HCl. It should be the same as the temperature of the NaOH solution. If not, take the average of the two temperatures as the initial temperature.

5. Quickly add the 1.00 M HCl from the beaker to the 1.00 M NaOH in the calorimeter. Stir gently with the thermometer. Record the highest temperature reached.

6. Calculate the amount of heat received or lost by the solution using the formula given on the first page. The mass of the solution is the sum of the masses of the two solutions. To determine the mass of a solution knowing its volume, assume that the density of the solution is 1.00 g/mL. The specific heat of the solution is assumed to be the same as that of water.

7. Is the neutralization reaction exothermic or endothermic?

CALORIMETRY

Calorimetry represents the study of heat flow. Heat is a form of energy that will pass spontaneously from an object with a higher temperature to one with a lower temperature, provided they are in contact. Given sufficient time, the two objects will reach the same temperature. Heat flow is ordinarily measured in a device called a calorimeter. A simple calorimeter consists of a container with insulated walls that is filled with water and a thermometer to measure temperature changes within the calorimeter. The insulation ensures that virtually no heat will be exchanged between the contents of the calorimeter and the surroundings. Within the calorimeter, chemical reactions are allowed to occur resulting in a transfer of heat either from the reaction to the water, resulting in an increase in the water temperature (exothermic reaction), or from the water to the reaction, resulting in a decrease in the water temperature (endothermic reaction). Since the walls of the calorimeter are (in theory) well insulated, changes in water temperature can be attributed to the heat that is evolved or consumed by the reaction. Of course, a small amount of heat does flow into and out of the calorimeter, but for the purpose of this lab we will neglect that amount.

When heat flows into a substance the temperature of that substance will increase. When heat is lost, the temperature will decrease. The quantity of heat, Q, required to cause a temperature change, ?T, in a substance is proportional to its mass, m, times the temperature change, as shown in the following equation: Q = m c ?T

The proportionality constant is called the specific heat, c, of that substance which can be considered the amount of heat required to raise the temperature of one gram of the substance by one degree Celsius. Heat is normally measured in units of joules (J). To raise the temperature of one gram of water by one Celsius degree, 4.18 J of heat must be added to the water. The specific heat of water is therefore 4.18 J/g?C. Ordinarily, heat flow into or out of a substance is measured by the temperature change of a known amount of water inside the calorimeter. The difference in temperature, ?T, represents the difference between the final temperature and the initial temperature of the substance (T_final