Determination of the Heat of Formation of Calcium Carbonate

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Experiment 6
Determination of the Heat of Formation of Calcium Carbonate

Name: Leung Dik Ka (14)

Name of partner: Lee Wai Chi (13)

Date: 5/11/2008

Title of the experiment: Determination of the Heat of Formation of Calcium Carbonate

Aims: To determinate the heat of formation of calcium carbonate by finding the temperature change in two reaction.


Introduction 
Heat of formation is the enthalpy change when one mole of product is formed from its constituent elements under standard conditions. The equation for the formation of calcium carbonate from its elements under standard conditions is
Ca
(s)+C (graphite)+O2 (g) →CaCO3(s).
The standard conditions are defined as elements or compounds in their normal physical states, under a pressure of 1 atm (101 325 Nm-2) and a temperature of 250C (298 K).

 
Procedure
A) Reaction of Calcium with dilute hydrochloric acid
1
.1g of calcium metal was weighed out approximately. The weighing was recorded.
2.100cm
3 of 1M hydrochloric acid was measured out by a measuring cylinder and
  was placed in a vacuum flask .
3. The temperature of the acid was determined and recorded.
4.The weighed portion of calcium was added and stirred thoroughly with the
  thermometer until all the metal had reacted.
5. The maximum temperature attained by the solution was recorded.

B) Reaction of calcium carbonate with hydrochloric acid
1.2g of dry, powdered calcium carbonate was weighed out into a clean plastic
  beaker.
2.100cm3 of 1M hydrochloric acid was measured out by a measuring cylinder and
  was placed in a vacuum flask.
3. The temperature of the acid was determined and recorded.
4.The weighed portion of calcium was added and stirred thoroughly with the
  thermometer until all the metal had reacted.
5. The maximum temperature attained by the solution was recorded.

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Result
A) Reaction of Calcium with dilute hydrochloric acid:

The ionic reaction for the reaction is Ca(s)+2H+(aq) →Ca2+ (aq) +H2 (g)


Assuming that the solution in the plastic beaker has the same soecific heat as water, the heat of formation of CaCl2 (aq) was released in the reaction between the calcium and the acid.

Assume that the density of the solution is the same as that of water, i.e. 1 g cm-3
Mass of the hydrochloric acid = 100 cm
3 × 1 g cm-3 = 100 g = 0.1 kg
Heat given out = 0.1
× 4200 ×25
           = 10.5 kJ
Number of moles of Ca = 1.00 ...

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