This concludes all of the calculations that were involved in all of the experiments. Next, we obtain a polystyrene cup to use as our calorimeter and fill it with 100 g of water. Accurately find the mass of a sample of solid ammonium nitrate of approximately 15 grams. The purpose of these three labs were to observe the nature of heat and reactions, which the experiments do rather nicely. The cup is placed within a 250-mL beaker to keep it in a sustained environment. Include the heat term in each equation.
This is otherwise known as the Law of Conservation of Energy. Students who served as a manager or computer operator will work as lab techs for this activity. Discuss Hess's law in terms of the law of conservation of energy and in terms of the three parts of this experiment. The main concept is to observe the change in enthalpy that results from the various reactions between strong and weak acids and bases. These holes could have let heat escape as the reaction was taking place which would have lowered the final temperature value.
Stir the mixture with the thermometer and record the highest temperature reached. Projects have included work on spinels, oxide superconductors and rock-forming minerals. See the introduction for helpful information and equations. This is called the molar heat of solution. C calculate the molar heat capacity Cm of water 4. The result gave us something like this: 23. In recent years, our research has expanded to materials with less well-defined structure stability fields and thermochemical properties.
You should use the above questions to guide your results and discussion, but there should be more to these sections than just answering the questions and they show flow logically as you discuss the lab and the results. In the solution, the ions have water molecules to take the places of their oppositely charged counterparts; and water molecules find ions more attractive then even other water molecules. For the results that were inaccurate, the source of error was most likely to due a miscalculation on my part, possibly in the calculation of the theoretical values, or the experimental for that matter. A lot of gas is forming. Carefully pour the MgO in and record the highest temperature that the reaction produces. Write the chemical equations for both of the reactions in this experiment. Add the sodium hydroxide solution to the acid solution in the styrofoam cup.
Turn the stirrer on slow. The format for finding the number of moles looked like the following: 2. Read through the procedure and look carefully at the data tables provided for you at the end of this lab. If you submit a paper version, you will need to show these calculations for one of the the trials. Since the percent error is a very small value it is evident that the experiment was a success, however this does not mean that it was perfect. Another discrepancy that may have occurred during the experiment was that the magnesium strip may have reacted with the oxygen in the air before it was poured into the calorimeter.
One error that may have caused a lower enthalpy of change value than expected could have been that heat escaped from the calorimeter used during the experiment. From your data, calculate the following for each part of the experiment. Ion-dipole forces are formed when the slightly positive hydrogen atoms are attracted to the negative ions, and the slightly negative oxygen atoms are attracted to the positive ions. Once again, the loss of heat would have resulted in a lower enthalpy value. The method for determining it is like so: 98. The mass of the cup with the water in it were recorded to find the exact mass of the water added. Then, when time was up, we used Graphical Analysis to print the resulting temperature vs.
Heat of formation is the change in enthalpy or energy that results when 1 mole of a compound is formed from its elements at standard state. Aluminum could also be tucked in the space between the lid and the calorimeter to once again lock the heat in. This means that heat was being produced immediately and the lid was not on the calorimeter to keep the heat from escaping. The temperature of the water and the calorimeter, originally at 22. So as the magnesium was being carried from the measuring area to the workstation or while it was sitting on the counter top or being poured in, it could have reacted with the oxygen in the atmosphere and combusted. In order to achieve maximum accuracy, we must know exactly how much heat will be lost, so that the results of the next two experiments will be as correct as possible. If you are submitting the report electronically, you may place formulas in spreadsheet cells instead.
Repeat steps 2-4, but replace the 200 mL of water with 200 mL of 0. The procedure is the same as the one used in the last experiment, except that the time interval is set to 4 minutes. Stir carefully with a thermometer until a constant temperature is reached. Reaction 1: The dissolving of solid sodium hydroxide in water. Objectives: To measure experimentally the amount of heat involved in the dissolving of ammonium nitrate and of sodium acetate in water. Consider the fact that dissolving is actually a two-step process. Write the net ionic equation for the reaction between solutions of potassium hydroxide and sulphuric acid.
Show how the 3 reactions adds and their enthalpy add to attain the desired reaction and H value. Experimental In order to do any calculation for energy, we first had to find the calorimeter constant. For every reaction, there were two different trials to improve the accuracy of our results. Dispose of solutions according to your teacher's instructions. Follow your instructor's directions for submitting this lab report. The rest of the numbers can be observed in Table 3-2.
Thermochemistry and Hess's Law Thermochemistry and Hess's Law Purpose To measure the enthalpy change of two different reactions in the laboratory. Use the appropriate function or formula to determine the minimum and maximum temperatures reached in each trial. If the molar mass of water is 18. Place the solid sodium hydroxide into the water in the cups. In this experiment, you will measure and compare the quantity of heat involved in three reactions.