5070_s20_qp_22
A paper of Chemistry, 5070
Questions:
10
Year:
2020
Paper:
2
Variant:
2
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1
Choose from the following chlorides to answer the questions. aluminium chloride ammonium chloride calcium chloride hydrogen chloride iron(chloride silver chloride sodium chloride Each chloride may be used once, more than once or not at all. Which chloride: contains a cation with a 2+ charge reacts with warm aqueous sodium hydroxide to form a gas which turns damp red litmus paper blue is insoluble in water has a molecule which has only 18 protons is a coloured solid at room temperature and pressure?
12. Experimental techniques and chemical analysis  →  12.5. Identification of ions and gases
10. Chemistry of the environment  →  10.1. Water
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2
Hydrogen reacts with oxygen as shown in the equation. 2H2+ O22H2OA sample containing 1.00 mol of hydrogen, H2, is completely combusted. This sample releases 286 kJ of heat energy. Calculate the heat energy released when 25.0 g of hydrogen is completely combusted. heat energy released kJ Use ideas about bond breaking and bond forming to explain why this reaction is exothermic. The reaction shown also represents the overall process that occurs within a hydrogen-oxygen fuel cell. Describe one advantage of using a hydrogen-oxygen fuel cell to power a motor vehicle rather than burning gasoline. Complete the equations for the two electrode reactions that happen in a hydrogen-oxygen fuel cell. H2 + 2e− O2 + 4H+ + 4e−
4. Electrochemistry  →  4.2. Hydrogen–oxygen fuel cells
5. Chemical energetics  →  5.1. Exothermic and endothermic reactions
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3
The table shows some properties of five esters. name structure relative molecular mass melting point / °C boiling point / °C methyl methanoate HCOOCH3 −100 methyl ethanoate CH3COOCH3 −98 methyl propanoate CH3CH2COOCH3 −88 methyl butanoate CH3CH2CH2COOCH3 −95 methyl pentanoate CH3CH2CH2CH2COOCH3 These esters are part of a homologous series. State the relative molecular mass of methyl pentanoate. Predict the boiling point of methyl pentanoate °C Explain why it is not possible to predict the melting point of methyl pentanoate. At 35 °C methyl methanoate is a gas. Explain how the data in the table shows this. Methyl pentanoate is used to flavour food. Suggest one other use for esters. Methyl propanoate is prepared by the reaction between propanoic acid and methanol. CH3CH2CO2H + CH3OH CH3CH2COOCH3 + H2O The forward reaction is exothermic. Calculate the maximum mass of methyl propanoate that can be made from 11.0 g of propanoic acid and excess methanol. Give the answer to three significant figures. mass of methyl propanoate g The temperature of the reaction mixture is increased. State and explain, in terms of particles, what happens to the rate of the forward reaction. The temperature of the reaction mixture is increased. State and explain what happens to the position of the equilibrium.
11. Organic chemistry  →  11.3. Fuels
6. Chemical reactions  →  6.3. Reversible reactions and equilibrium
12. Experimental techniques and chemical analysis  →  12.4. Separation and purification
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4
Part of the reactivity series is shown. magnesium more reactive aluminium zinc chromium iron less reactive Predict the names of the products formed when chromium reacts with dilute hydrochloric acid. Powdered zinc is added to aqueous chromium(ions, Cr3+. Construct an ionic equation, with state symbols, for this reaction. Explain why aluminium does not react with water. Hydrogen peroxide, an oxidising agent, is added to aqueous potassium iodide in a test-tube. Describe the colour change seen in the test-tube. Chromium is extracted by the reaction of aluminium with chromium(oxide, Cr2O3. Write the equation for this reaction. Suggest a compound that can reduce chromium(oxide to chromium metal. State one advantage of recycling metals.
9. Metals  →  9.4. Reactivity series
9. Metals  →  9.6. Extraction of metals
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5
Sulfuric acid, H2SO4, reacts with sodium hydroxide, NaOH, as shown. H2SO4+ 2NaOHNa2SO4+ 2H2OA sample of 25.0 cm3 of 0.0500 mol / dm3 H2SO4 is placed in a beaker. NaOHis added slowly, from a burette, to the H2SO4 in the beaker. A pH probe is used to measure the pH of the solution in the beaker until a total of 40.0 cm3 of NaOHis added. The graph shows how the pH of the solution in the beaker changes. pH volume of NaOHadded / cm3 Explain, in terms of the ions present, why the pH of the solution in the beaker changes from 1.0 to 13.0. Use the graph to state the volume of NaOHthat just neutralises all of the H2SO4. volume of NaOHcm3 Use your answer to to calculate the concentration, in mol / dm3, of the NaOH. concentration of NaOHmol / dm3
7. Acids, bases and salts  →  7.1. The characteristic properties of acids and bases
3. Stoichiometry  →  3.3. The mole and the Avogadro constant
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6
The structures of two alcohols are shown. H C C H H H H O H H C C H H H H C C O H H H H H ethanol alcohol B What is the name of alcohol B? Draw the structure of one other alcohol which is an isomer of B. Show all of the atoms and all of the bonds. Ethanoic acid is produced by the oxidation of ethanol. State the reagent for this reaction. Ethanol is a simple molecular compound. Explain why liquid ethanol does not conduct electricity. Ethanol can be dehydrated to form ethene, C2H4. Describe, using a dot-and-cross diagram, the bonding in a molecule of ethene. Only include the outer shell electrons.
11. Organic chemistry  →  11.6. Alcohols
2. Atoms, elements and compounds  →  2.5. Simple molecules and covalent bonds
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7
This question is about some of the oxides of the elements in Period 3. State the electronic configuration of the negative ion in sodium oxide, Na2O. Magnesium oxide is an insoluble base that can be used to prepare pure magnesium sulfate crystals. Describe the essential practical details for the preparation of pure magnesium sulfate crystals from magnesium oxide. An oxide of phosphorus contains 43.7% by mass of phosphorus. Show that the empirical formula for this oxide is P2O5. A sample of this oxide has a mass of 2.56 g. The sample contains 0.00901 mol of the oxide. Calculate the relative molecular mass and hence the molecular formula for this oxide of phosphorus. relative molecular mass molecular formula State the structure and bonding in silicon dioxide, SiO2.
3. Stoichiometry  →  3.2. Relative masses of atoms and molecules
2. Atoms, elements and compounds  →  2.2. Atomic structure and the Periodic Table
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8
Copper is a transition element. State two properties that are typical of the compounds of a transition element. Aqueous copper(sulfate reacts with aqueous potassium iodide. The ionic equation for this reaction is shown. 2Cu2++ 4I−2CuI+ I2Explain how this equation shows that the reaction involves oxidation. Anhydrous copper(sulfate decomposes when heated strongly. CuSO4CuO+ SO3A sample of 6.40 g of CuSO4 is heated until all of the sample has thermally decomposed. Calculate the volume of sulfur trioxide formed, in dm3, measured at room temperature and pressure. volume of sulfur trioxide dm3 Iron reacts with aqueous copper(sulfate to make aqueous iron(sulfate and copper. Construct the ionic equation for this reaction. Suggest one observation that would be seen during this reaction. Describe a chemical test that can be used to distinguish between aqueous solutions of iron(sulfate and copper(sulfate. chemical test result with iron(sulfate result with copper(sulfate
4. Electrochemistry  →  4.1. Electrolysis
9. Metals  →  9.4. Reactivity series
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9
Sulfur dioxide is a colourless gas which can be found in air. State one environmental problem caused by the presence of sulfur dioxide in air. When heated in air iron pyrite, FeS2, reacts with oxygen. Sulfur dioxide and iron(oxide, Fe2O3, are the products of this reaction. Construct the equation for this reaction. Give one use for sulfur dioxide. Liquid sulfur dioxide is stored in cylinders. When the cylinder is opened the liquid quickly changes into a gas. Use the kinetic particle theory to describe the changes in movement and arrangement of the particles when liquid sulfur dioxide becomes a gas. Sulfur dioxide has a low melting point. Suggest, in terms of structure and bonding, why sulfur dioxide has a low melting point. Describe the chemical test for sulfur dioxide. test observation
6. Chemical reactions  →  6.3. Reversible reactions and equilibrium
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10
Fractional distillation and cracking are important processes in the conversion of petroleum (crude oil) into useful hydrocarbons. Fractional distillation separates petroleum (crude oil) into fractions such as bitumen and naphtha. Which physical property allows the petroleum (crude oil) to be separated into fractions? Describe the separation of petroleum (crude oil) by fractional distillation. Give one use of the bitumen fraction. The naphtha fraction is used as a chemical feedstock. One of the hydrocarbons in naphtha has the molecular formula C10H22. Use the general formula for an alkane to show that C10H22 is an alkane. In an experiment C10H22 is cracked to form products A, B and C. Product A gives a squeaky pop when ignited with a burning splint. Identify product A. Product B has a relative molecular mass of 98 and decolourises aqueous bromine. Suggest the molecular formula for B. Explain your answer. molecular formula explanation Product C can be polymerised to give the polymer shown. H H C C H CH3 n Draw the structure of product C.
11. Organic chemistry  →  11.3. Fuels
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