6. Chemical reactions
A section of Chemistry, 5070
Listing 10 of 377 questions
Cerium is a metal with a relative atomic mass of 140. Cerium powder reacts with sulfuric acid. 2Ce+ 3H2SO4Ce2(SO4)3+ 3H2Describe and explain, using ideas about collisions between particles, how the rate of this reaction changes when the concentration of sulfuric acid is decreased. All other conditions stay the same. Describe and explain how the rate of this reaction changes when large pieces of cerium are used instead of cerium powder. All other conditions stay the same. The reaction of cerium with sulfuric acid is exothermic. Complete the energy profile diagram to show the enthalpy change for this reaction. progress of reaction energy Calculate the maximum volume of hydrogen, in dm3, formed when 12.6 g of cerium reacts with excess sulfuric acid at room temperature and pressure. [Ar: Ce, 140] volume dm3 The formula of cerium carbonate is Ce2(CO3)3. Calculate the percentage by mass of cerium in cerium carbonate. %
5070_w18_qp_21
THEORY
2018
Paper 2, Variant 1
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This question is about compounds containing chlorine. The equation shows the reaction of aqueous methanol with hydrochloric acid. CH3OH+ HCl CH3Cl + H2OThe progress of this reaction can be followed by taking small samples of the reaction mixture every hour and determining the concentration of hydrochloric acid. Describe a practical method by which the concentration of hydrochloric acid can be determined in a sample. The graph shows how the concentration of hydrochloric acid changes as the reaction proceeds. 0.20 0.40 time in hours concentration of HCl in mol / dm3 0.60 0.80 1.00 1.20 1.40 1.60 1.80 A B C D Deduce the concentration of hydrochloric acid four hours from the start of the experiment. mol / dm3 At which point on the graph, A, B, C or D, is the rate of reaction fastest? Give a reason for your answer by referring to the graph. Describe and explain, using ideas about collisions between particles, how the rate of a reaction changes when the temperature is decreased. All other conditions stay the same. Describe the effect of hydrochloric acid on Universal Indicator paper. Name a metal chloride that is insoluble in water. Chlorofluorocarbons (CFCs) diffuse into the atmosphere. Describe the effect of CFCs on the atmosphere and explain why this is a problem. effect explanation
5070_w19_qp_21
THEORY
2019
Paper 2, Variant 1
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The equation shows the reaction of calcium carbonate with hydrochloric acid. CaCO3+ 2HCl CaCl 2+ CO2+ H2OThe rate of this reaction can be determined by measuring the decrease in mass of the reaction mixture. Describe one other method of following the progress of this reaction. Describe and explain, using ideas about collisions between particles, how the rate of reaction changes when the same mass of calcium carbonate is used in smaller pieces. All other conditions stay the same. Describe and explain, using ideas about collisions between particles, how the rate of reaction changes when the temperature is increased. All other conditions stay the same. Calculate the minimum mass of calcium carbonate, in grams, needed to produce 16.8 cm3 of carbon dioxide at room temperature and pressure. Give your answer to three significant figures. mass of calcium carbonate g Describe a test for carbon dioxide. test observation Calcium hydroxide can be used to control the pH of the soil. Explain how calcium hydroxide controls the pH of the soil.
5070_w19_qp_22
THEORY
2019
Paper 2, Variant 2
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A drop of black ink is placed at the bottom of a beaker of water. After a time, the colour of the ink spreads throughout the water. Explain this observation in terms of the kinetic particle theory. In the past, ink was made from a mixture containing iron(ions and tannic acid. Describe a test for iron(ions. test observations The ink darkens when used on paper. This is because iron(ions are oxidised to iron(ions. Write the ionic equation for this reaction. After a time, the ink fades because of a hydrolysis reaction which is catalysed by acids. State how a catalyst increases the rate of a chemical reaction. Paper is made of cellulose. Cellulose is a complex carbohydrate . Name one other complex carbohydrate . Describe how complex carbohydrates can be hydrolysed to simple sugars.
5070_w20_qp_22
THEORY
2020
Paper 2, Variant 2
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377