Magnesium reacts with hydrochloric acid to make magnesium chloride and hydrogen gas

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Russell Kennedy
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1 Experiment 1: Magnesium and Hydrochloric acid Magnesium reacts with hydrochloric acid to make magnesium chloride and hydrogen gas Equation: Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g) gas syringe 50 cm 3 dilute hydrochloric acid In two experiments, two equal masses of magnesium ribbon were allowed to react with two 50 cm 3 portions of dilute hydrochloric acid. The gas produced was collected in a gas syringe (as shown opposite) so that its volume could be measured. magnesium ribbon In first experiment, the temperature of the acid was 20 C; in the second experiment the temperature was 50 C The results are shown in the table below. Volume of gas collected Time (cm 3 ) (minutes) Experiment at 50 C Experiment at 20 C Describe the differences between the two sets of results 3. How do you explain the differences between the two sets of results? 4. If the experiment was repeated at 35 C how would it affect: a) the rate of the reaction; b) the total amount of gas produced?

2 Experiment 2: Hydrogen peroxide and Manganese oxide When hydrogen peroxide (H2O2) is left to stand in a clear glass container, it slowly decomposes to produce oxygen and water Equation: H2O2(aq) H2O(l) + O2(g) Manganese oxide (MnO2) acts a catalyst for this reaction: it speeds up the reaction but is not used up in the reaction itself delivery tube bung measuring cylinder 25 cm 3 hydrogen peroxide solution lump of manganese oxide trough water 25cm 3 of hydrogen peroxide solution was placed in a boiling tube fitted with a delivery tube. Any oxygen produced was collected over water in an up-turned measuring cylinder. The experiment was carried out with just hydrogen peroxide. It was then repeated, adding a solid lump of manganese dioxide. Finally, the manganese dioxide was removed, ground into a fine powder in a pestle and mortar: the experiment was then repeated using the powdered manganese oxide. The results produced are shown in the table below 1. Plot a suitable graph of the results 2. Describe the effects of grinding up the manganese oxide 3. How do you explain the effect of grinding up the manganese oxide? 4. Explain why it is possible to reuse the lump of manganese oxide

3 Time (seconds) Volume of oxygen produced (cm 3 ) No MnO2 0.5g of added powdered 0.5g lump of MnO2 added MnO2 added

4 Experiment 3: Calcium carbonate and sulphuric acid Calcium carbonate (CaCO 3) reacts with sulphuric acid to make calcium sulphate, water and carbon dioxide Equation: CaCO 3(s) + H 2SO 4(aq) CaSO 4(aq) + H 2O (l) + CO 2(g) conical flask 25 cm 3 sulphuric acid cotton wool 10g of marble chips A conical flask containing 25.0cm 3 of dilute sulphuric acid was placed on an electronic balance 10.0g of marble chips - which are composed of calcium carbonate were added, and the neck of the flask was stoppered with cotton wool. g The mass of the flask and its contents were measured at the start of the reaction and at two minute intervals. The results are shown in the table below Time (minutes) Mass of flask and contents Describe the trend shown in the rate of the reaction 3. Explain changes in the rate of reaction 4. How much carbon dioxide is produced during this experiment? How long does it take for this mass of carbon dioxide to be produced? How long does it take to produce half the total mass?

5 Experiment 4: Sodium thiosulphate and hydrochloric acid Sodium thiosulphate (Na2S2O3) reacts with hydrochloric acid to produce sulphur and sulphur dioxide. The sulphur is a solid which forms a yellow suspension 1 : the reaction mixture turns cloudy and then opaque. Equation: Na2S2O3(aq) + 2HCl(aq) 2NaCl(aq) + SO2(g) + H2O(l) START Top View END 50 cm 3 of sodium thiosulphate solution Solid sulphur is deposited obscuring X underneath flask 10 cm 3 hydrochloric acid 50 cm 3 of 0.1M sodium thiosulphate solution was placed in a conical flask. A cross was drawn on a piece of paper and placed underneath the flask 10cm 3 of 1M hydrochloric acid was added and the flask swirled to mix. The time taken for the cross to disappear was recorded. 1 A suspension is a mixture of fine solid particles floating in a liquid

6 The experiment was repeated with different concentrations of sodium thiosulphate The results are shown in the table below Concentration of Na2S2O3 (M) Time taken for X to disappear (s) Describe the trend shown in your graph 3. How do you explain the effect of thiosulphate concentration on the rate of the reaction? 4. Add a line to your graph showing how you would expect the results to change if you used 0.5M instead of 1.0M hydrochloric acid

7 Experiment 5: Calcium carbonate and hydrochloric acid Calcium carbonate (CaCO 3) reacts with hydrochloric acid to make calcium chloride, water and carbon dioxide Equation: CaCO 3(s) + HCl (aq) CaCl 2(aq) + H 2O (l) + CO 2(g) delivery tube 25 cm 3 of hydrochloric acid were placed in a boiling tube. bung 25cm 3 hydrochloric acid indigestion tablet water An indigestion tablet made of calcium carbonate was added, and the boiling tube fitted with a bung and delivery tube the other end of the delivery tube was placed in a boiling tube of water. The number of bubbles produced in 1 minute were recorded The experiment was repeated several times, with the tablet being broken into different numbers pieces each time The results are shown in the table below How many pieces the tablet was broken into Number of bubbles produced in 1 minute 1 (Whole) Describe the trend shown in your graph 3. How do you explain the effect of breaking up the indigestion tablet on the rate of the reaction? 4. Suggest a reason why there is little difference between the results when the tablet is broken into 5 pieces compared with when it is broken into 6 pieces

Composition of Air. Air is a mixture of different gases. Gas % Nitrogen 78% Oxygen 21% Argon 1% Carbon Dioxide 0.04%

Composition of Air. Air is a mixture of different gases. Gas % Nitrogen 78% Oxygen 21% Argon 1% Carbon Dioxide 0.04% The Atmosphere Composition of Air Air is a mixture of different gases Gas % Nitrogen 78% Oxygen 21% Argon 1% Carbon Dioxide 0.04% Water Vapour Varies day to day Experiment to show 1/5 of air is oxygen