Unit 1 Worksheet 1 Nature of matter and chemical change
1. State the equation (including state symbols) for the following reactions:
i. The addition of dilute hydrochloric acid to solid calcium carbonate to give aqueous calcium
chloride, carbon dioxide and water.
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ii. The reaction between ammonia gas and oxygen gas to give nitrogen(II) oxide gas and water.
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2. State the ionic equation for the following reactions.
i. BaCl2(aq) + 2AgNO3(aq) → Ba(NO3)2(aq) + 2AgCl(s)
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ii. Na2CO3(aq) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + H2O(l)
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3. Outline how the following mixtures could be separated into their individual components.
i. A saturated solution of sodium chloride
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ii. A mixture of hexane and octane
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iii. An ink that contains two coloured dyes.
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4. The diagram below shows a cooling curve for stearic acid.
i. Determine the melting point of stearic acid.
ii. Explain why the temperature remains constant between B and C.
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5. The metal tungsten, W, can be prepared by reducing powdered tungsten(VI) oxide using hydrogen
gas at 850 oC. The equation for the reaction is:
WO3(s) + 3H2(g) → W(s) + 3H2O(g)
Calculate the atom economy for this reaction.
Answers
1. i. 2HCl(aq) + CaCO3(s) → CaCl2(aq) + CO2(g) + H2O(l)
ii. 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(l)
2. i. Cl–(aq) + Ag+(aq) → AgCl(s)
ii. CO32–(aq) + 2H+(aq) → CO2(g) + H2O(l)
3. i. Distillation (to remove all the water)
ii. Fractional distillation (as hexane boils at 68 oC and octane boils at 125 oC).
iii. Paper chromatography (or thin layer chromatography).
4. i. 70 oC (where the straight line extrapolated from BC crosses the temperature axis).
ii. The stearic acid is changing state. As the liquid condenses to the solid heat is given out which
counteracts the cooling. The temperature only starts to decrease again when all the liquid has turned
into solid at point C.
5. WO3(s) + 3H2(g) → W(s) + 3H2O(g)
Ar (W) = 183.84; Mr (H2O) = 18.02
Total mass of products = 183.84 + (3 x 18.02) = 237.9 g
Atom economy = 183.84/237.9 x 100 = 77.3%