CHM271 EXP Datasheet EXP 1 PDF

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CHM271 LABORATORY MARCH 2021 - AUGUST 2021INSTRUCTIONS TO STUDENTS:Complete the datasheet for the following experiment. DATASHEET EXPERIMENT 1: THERMOCHEMISTRY – HESS’S LAW Table: Mass and Temperature of SubstancesMagnesium (Mg) Magnesium oxide (MgO) Mass, m (g) 0 1.Initial temperature (°C) 27 27.Fi...

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CHM2 7 1LABORATORY

MARCH2 0 2 1-AUGUST2 0 2 1

INSTRUCTIONS TO STUDENTS: Complete the datasheet for the following experiment. DATASHEET EXPERIMENT 1: THERMOCHEMISTRY – HESS’S LAW Table: Mass and Temperature of Substances Magnesium (Mg)

Magnesium oxide (MgO)

Mass, m (g)

0.60

1.00

Initial temperature (°C)

27.0

27.0

Final temperature (°C) (HCl + Mg or MgO)

74.0

51.0

Temperature change (∆T)

47.0

24.0

Volume of acid is used = 30.0 mL Mass of acid, ma = 30.0 g (assume density of acid is 1g mL-1)

Questions 1) Calculate ∆� 2 and ∆�3 1) ∆Q2 = [ (m x c x ∆T) / 1000] kJ

2) ∆Q3 = [ (m x c x ∆T) / 1000] kJ

= (30 x 4.2 x 47.0) /1000

= (30 x 4.2 x 24.0) / 1000

= 5.922 kJ

= 3.024 kJ

∆H2 = ∆Q1 / n

∆H3 = ∆Q3 / n

= 5.922 / (0.60/24.31)

= 3.024 / [1.00/(24.31+16.00)]

= 5.922 / 0.025

= 3.024 / 0.025

= 236.88 kJ mol

-1

= 120.96 kJ mol-1

2) State whether the reaction is endothermic or exothermic = exothermic 3) Calculate ∆�1, the standard enthalpy of formation of magnesium oxide. Give that the enthalpy of formation of water (value of ∆�4) is − 286 ��� ��-1 ∆�1 = ∆�2∆+ (- ∆

∆ ) + ∆4

3

= 236.88 + (-120.96) + (-286.00) = -170.08 kJ mol-1...