CHEM 110 Lecture Notes - Lecture 5: Magnesium Oxide, Joule, Magnesium

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ochrebat842

11 May 2018

School

Simon Fraser University

Department

Chemistry

Course

CHEM 110

Professor

Stephen Collis

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Experiment B2: The Determination of an Enthalpy Change that Cannot Be Measured Directly

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Report Form:

A. Determination of the Heat Capacity of the Calorimeter

Trial 1

Time

Temperature (°C)

Before Mixing Cold

20°C

Before Mixing Hot

41°C

After mixing

0.15s

31°C

0.30s

28°C

0.45s

28°C

60.0s

28°C

1min 15s

28°C

1min 30s

28°C

1min 45s

27.5°C

2min

28°C

2min 15s

28.5°C

2min 30s

28.5°C

2min 45s

28.5°C

3min

28°C

Trial 2

Time

Temperature (°C)

Before Mixing Cold

14°C

Before Mixing Hot

44°C

After mixing

0.15s

31°C

0.30s

29°C

0.45s

27°C

60.0s

27°C

1min 15s

27°C

1min 30s

26.5°C

1min 45s

26.5°C

2min

27°C

2min 15s

26.5°C

2min 30s

26.5°C

2min 45s

26°C

3min

26.5°C

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Graphs

Trial 1:

Trial 2:

Part B: Determination of the Enthalpy of Formation of Magnesium Oxide

Magnesium Reaction

Trial 1 Mass of Mg = 0.12g

Mol of Mg = 0.0049mol

Trial 2 Mass of Mg = 0.12g

Mol of Mg = 0.0049mol

025 50 75 100 125 150 175 200

Temperature(°C)

025 50 75 100 125 150 175 200

TEMPERAT U RE ( °C)

Temperature(°C)

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Document Summary

Experiment b2: the determination of an enthalpy change that cannot be measured directly. Report form: determination of the heat capacity of the calorimeter. T e m pe r at u r e ( c ) Part b: determination of the enthalpy of formation of magnesium oxide. 0. 0062mol (1mol h2o(l))(-285. 8kj/mol)-(1mol h2(g))(0kj/mol)+( mol o2(g))(0kj/mol) (-285. 5kj/mol)-(0kj/mol) Hf(reaction)= -285. 5kj/mol (aq) mg2+ (aq) + h2 (g: mg(s) + 2h+ T = 31. 7 c -21. 7 c = 10 c x = 0. 25g mg. 0. 12/24. 31 g/mol = 0. 0049 mol mg q = mc t q = 100 g hcl x 4. 18 j/g c x 10 c q = 4180 j 4. 180 kj. 4. 180/0. 0049= -503. 07 kj/mol (aq) (aq) h2o (l) + mg2: mgo(s) + 2h+ T = 30. 2 c -22. 1 c = 8. 1 c. 1. 040 g mgo/ 40. 31 = 0. 0258 mol mgo q = mc t q = 100 g hcl x 4. 184 j/g c x 8. 1 c q = 3389. 04 j or 3. 38904 kj.

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