Determination of the Heat of Formation of Calcium and Calcium Carbonate

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Chemistry

Laboratory report 6 –

Determination of the Heat of Formation of Calcium and Calcium Carbonate

Name: Suen Wing Sze

Name of partner: Sher Wai Kei

Date: 5/11/2008

Title of the experiment: Determination of the heat of formation of calcium and calcium carbonate

Aims: To determinate the amount of heat energy liberated when calcium reacts with dilute hydrochloric acid and when calcium carbonate reacts with dilute hydrochloric acid.

Introduction: 1.  Heat of formation is the enthalpy change of the reaction when one mole of substance is formed from its constituent elements in the standard states under standard conditions.

2.  Ca(s) + C(graphite) + O2(g) → CaCO3(aq)

3.  Standard conditions of thermochemistry are defined as :

(a) elements or compounds in their normal physical states,

(b) a pressure of 1 atm (101325 Nm-2), and

    (c) a temperature of 25 (298 K).

Reaction of calcium with dilute hydrochloric acid

Procedure:

  1. Approximately excess 1g of calcium metal had been weighed out. The weighing was then being recorded (two decimal places is sufficient accuracy).
  2. Measuring cylinder had been used to measure out 100cm3 of approximately 1M hydrochloric acid and place it in a vacuum flask.
  3. The temperature of the acid had been determined and recorded.
  4. Then the weighted portion of calcium was added and the solution had been stirred thoroughly with a stirrer until all the metal had been reacted.
  5. The maximum temperature attained by the solution had been record.
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Data:

Discussion:

4.  Ca(s) + 2H+(aq) → Ca2+(aq) + H2(g)

5.  Heat of formation of calcium chloride will be evolved.

6.  E = mcT

= (100)(4.2)(28.5)

= 11970 J  

 The heat evolved in the reaction between calcium and acid is 11.970 kJ.

Number of mole of calcium used =  

                           = 0.02569 mol

Heat would have been evolved by one mole of calcium atoms

=

=  465.94 kJ mol-1

  1. In the calculation, only the mass of calcium is the limiting factors. The concentration and ...

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