Question

procedure
part 1: determining δh of reaction (2)

1. read the procedure for part 1. prepare a data table to record mass and temperature data.
2. set up the simple calorimeter. using a graduated cylinder, add 100 ml of 1.00 mol/l hcl(aq) to the calorimeter.
3. record the initial temperature, t_initial, of the hcl(aq), to the nearest tenth of a degree.
4. find the mass of no more than 0.80 g of mgo(s) powder. record the exact mass.
5. add the mgo(s) powder to the calorimeter containing the hcl(aq). swirl the solution gently, recording the highest temperature, t_final, reached.
6. dispose of the reaction solution as directed by your teacher.

part 2: determining δh of reaction (3)

1. read the procedure for part 2. prepare a data table to record mass and temperature data.
2. using a graduated cylinder, add 100 ml of 1.00 mol/l hcl(aq) to the calorimeter.
3. record the initial temperature, t_initial, of the hcl(aq) to the nearest tenth of a degree.
4. if you are using magnesium ribbon (as opposed to turnings), sand the ribbon. accurately determine the mass of no more than 0.50 g of magnesium. record the exact mass.
5. add the mg(s) to the calorimeter containing the hcl(aq). swirl the solution gently, recording the highest temperature, t_final, reached.
6. dispose of the solution as directed by your teacher.

analyze and interpret

1. determine the enthalpy of reactions for reactions (2) and (3). list any assumptions you make and explain why they are valid assumptions.
2. write thermochemical equations for reactions (2) and (3) using δh notation. ensure the signs you use are correct.
3. algebraically combine equations (2), (3), and (4), and their corresponding δh values, to arrive at equation (1) and the molar enthalpy of combustion of magnesium.
4. draw an enthalpy diagram to represent the combining of equations (2), (3), and (4) to obtain equation (1) and the molar enthalpy of combustion of magnesium.
5. compare your result with the accepted value of δh_comb for magnesium. calculate your percent error.
6. suggest some sources of error in the procedure. in what ways could you improve the procedure?

conclude and communicate

1. explain how you used hess’s law to determine δh for the combustion of magnesium. state the result you obtained for the thermochemical equation that corresponds to chemical equation (1).

extend further
inquiry design an investigation to test hess’s law by using the following equations:
(1) naoh(s) → naoh(aq)
(2) naoh(s) + hcl(aq) → nacl(aq) + h₂o(ℓ)
(3) naoh(aq) + hcl(aq) → nacl(aq) + h₂o(ℓ)
assume you have a simple calorimeter, naoh(s), 1.00 mol/l hcl(aq), 1.00 mol/l naoh(aq), and standard laboratory equipment. write a step-by-step procedure for the investigation. then outline a plan for analyzing your data. be sure to include appropriate safety precautions. if time permits, obtain your teacher’s approval and carry out the investigation.
research burning magnesium not only creates a very bright light but it also burns at a very high temperature. research ways in which people have used the bright light and high temperatures in the past and currently.

Explanation:

The problem involves determining enthalpy changes of reactions, using Hess's law, and calorimetry, which falls under the subfield of Chemistry (a subfield of Natural Science) as it deals with chemical reactions, thermochemistry, and experimental procedures related to chemical energy changes.

Answer:

Natural Science - Chemistry