Determination of the Relative Atomic Mass of Calcium
In this experiment, I will determine the relative atomic mass of
calcium by two different methods.
v By measuring the volume of hydrogen produced.
v By titrating the lithium hydroxide produced.
Method 1
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v 0.10g of calcium used.
v 100cm3 of distilled water used.
Results
Method 1
Mass of Calcium (g)
Total volume of gas produced (cm3)
0.10
37
v Starting point of water in cylinder = 238cm3
v Ending point, after reaction complete, of water in cylinder= 201cm3
v (238 - 201 = 37) Deduction of 37cm3, therefore 37cm3 of hydrogen gas
produced.
1 mol of gas occupies 24000 cm3 at room temperature and pressure.
Ca (s) + 2H2O (l) à Ca(OH)2 (aq) + H2 (g)
v Number of moles of hydrogen = volume of hydrogen / 24000
= 37/24000 = 0.0015416 mol
= 0.001542 mol (4sf)
v Number of moles of calcium = 0.001542 (ratio 1:1 with hydrogen)
v Relative atomic mass of calcium = Mass of calcium / Moles
= 0.10 / 0.001542 = 64.85084
= 64.85 (4sf)
Method 2
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v 25.0cm3 of alkaline solution used.
v Amount of acid used:
Starting Amount of HCl used (cm3)
Amount of acid used till reaction complete- Test 1 (cm3)
Test 2 (cm3)
Test 3 (cm3)
Average (cm3)
100
9.00
8.20
8.20
8.47
Results
Ca(OH)2 (aq) + 2HCL (aq) à CaCl2 (aq) + 2H2O (l)
v Moles of hydrochloric acid used in titration = volume *
concentration
= 0.1 * (8.47/1000) = 0.0.000847
= 0.0008470 mol ( 4sf)
v Moles of Ca(OH)2 = the number of moles of HCl / 2 (as the ratio is 2
: 1) = 0.0008470 / 2 = 0.0004235 mol (4sf)
v Moles of Ca(OH)2 present in 100cm3 of alkaline solution = 0.
Number of moles of〖 K_2 CrO〗_4, mol = (4.0 ×〖10〗^(-2) mol L^(-1))(5.0×〖10〗^(-2) L)= 2.0×〖10〗^(-3) mol
10cm3 of 1 molar solution. I will use 3 of each solution to ensure that
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The amount of hydrochloric acid. 3. The concentration of the hydrochloric acid. 4. The surface area of the calcium carbonate.
The aim is to find out if changing the concentration of the hydrochloric acid solution has an effect on the time taken for the reaction. The reaction that will take place is: Hydrochloric acid + Calcium Carbonate + Calcium Chloride + Water + Carbon dioxide 2HCl (aq) + CaCo3 (s) CaCL2 (aq) + H2O + CO2 (g). Collision theory - Collisions between reactant particles are needed. for the reaction to take place in order to form a product.
Moles Volume HCl Volume Water 2 M 10 cm 3 0 cm 3 1.5 M 7.5 cm 3 2.5 cm 3 1 M 5 cm 3 5 cm 3 0.5 M 2.5 cm 3 7.5 cm 3
NaOH * 1mol HCl/1mol NaOH=.00925mol HCl. .00925mol HCl/.005L =.185 M HCl.
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* In method (1), due to the oil that lithium is stored in, not only