0620_m18_qp_42
A paper of Chemistry, 0620
Questions:
5
Year:
2018
Paper:
4
Variant:
2
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1
This question is about gases. The following substances are gases at room temperature. letter A B C D E F G H substance SO2 Ar CO Cl 2 NH3 CO2 CH4 C3H8 Identify, by letter: a gas which combines with water to form acid rain two gases which exist as diatomic molecules a gas which bleaches damp litmus paper a gas which is used as an inert atmosphere in lamps two gases which are found in clean dry air two gases which are found in refinery gas. NF3 has covalent bonds. What is a covalent bond? Complete the dot-and-cross diagram to show the electron arrangement in a molecule of NF3. Show outer shell electrons only. N F F F  Air is a mixture. Nitrogen and oxygen are the two most common gases in air. What is meant by the term mixture? State the percentage of oxygen, to the nearest whole number, in clean dry air. Describe the steps in the industrial process which enables nitrogen and oxygen to be separated from clean dry air. Use scientific terms in your answer. Which physical property of nitrogen and oxygen allows them to be separated? 
10. Chemistry of the environment  →  10.3. Air quality and climate
1. States of matter  →  1.1. Solids, liquids and gases
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2
Sodiumchloride is a typical ionic compound. The diagram shows part of a lattice of sodiumchloride. Complete the diagram to show the ions present. Use ‘+’ for Na+ ions and ‘–’ for Cl – ions. One ion has been completed for you. +  How many electrons does a chloride ion have? Identify an element which has atoms with the same number of electrons as a sodium ion. Electrolysis of concentrated aqueous sodiumchloride is an important industrial process. What is meant by the term electrolysis? Name the products of the electrolysis of concentrated aqueous sodiumchloride.  Write an ionic half-equation for the reaction at the cathode. Include state symbols. Silver chloride can be made by reacting aqueous sodiumchloride with aqueous silvernitrate. The other product of the reaction is sodiumnitrate. The chemical equation for the reaction is shown. NaCl + AgNO3AgCl + NaNO3A student attempted to make the maximum amount of sodiumnitrate crystals. The process involved three steps. step 1 The student added aqueous sodiumchloride to aqueous silvernitrate and stirred. Neither reagent was in excess. step 2 The student filtered the mixture. The student then washed the residue and added the washings to the filtrate. step 3 The student obtained sodiumnitrate crystals from the filtrate. Describe what the student observed in step1. Why was the residue washed in step2? Give the names of the two processes which occurred in step3.  The student started with 20 cm3 of 0.20 mol / dm3 NaCl . ● ● Determine the amount of NaCl used.  amount of NaCl used = mol The yield of NaNO3 crystals was 90%. ● ● Calculate the mass of NaNO3 crystals made.  mass of NaNO3 crystals = g  Write a chemical equation for the action of heat on sodiumnitrate crystals. 
4. Electrochemistry  →  4.1. Electrolysis
9. Metals  →  9.4. Reactivity series
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3
Limestone rock is mainly calciumcarbonate, CaCO3. The ‘limestone cycle’ is shown. Each step is numbered. limestone calcium carbonate CaCO3limewater calcium hydroxide Ca(OH)2slaked lime calcium hydroxide Ca(OH)2lime step 2 add limited water step 4 add CO2 step 3 add an excess of water step 1 heat Complete the box to give the chemical name and formula of lime. Which step involves a physical change? What type of reaction is step1? Suggest how step2 could be reversed. Write a chemical equation for step4. Explain why step4 is a neutralisation reaction. Refer to the substances reacting in your answer. Dolomite is a similar rock to limestone. Dolomite contains magnesiumcarbonate, MgCO3. Write a chemical equation for the reaction between magnesiumcarbonate and dilute nitricacid. Forsterite is another rock which contains a magnesium compound. A sample of forsterite has the following composition by mass: Mg, 2.73 g; Si, 1.58 g; O, 3.60 g. Calculate the empirical formula of forsterite.  empirical formula = 
12. Experimental techniques and chemical analysis  →  12.5. Identification of ions and gases
9. Metals  →  9.4. Reactivity series
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4
Ammonia is an important chemical. Ammonia is a base. In chemistry, what is meant by the term base? Write a word equation to show ammonia behaving as a base. Ammonia reacts with chlorine. The chemical equation is shown. 2NH3+ 3Cl 2N2+ 6HCl Calculate the volume of chlorine, measured at room temperature and pressure, needed to react completely with 0.68 g of ammonia.  volume of chlorine = cm3 The chemical equation can be represented as shown. H H H + + Cl Cl N N N Cl H Use the bond energies in the table to determine the energy change, ΔH, for the reaction between ammonia and chlorine. bond bond energy in kJ / mol N–H Cl –Cl N≡N H–Cl ● ● energy needed to break bonds  kJ ● ● energy released when bonds are formed  kJ ● ● energy change, ΔH, for the reaction between ammonia and chlorine  kJ  Is the reaction endothermic or exothermic? Explain your answer. Ammonia reacts with oxygen at high temperatures in the presence of a suitable catalyst to form nitricoxide, NO. 4NH3+ 5O24NO+ 6H2OExplain how this chemical equation shows ammonia acting as a reducing agent. Suggest a suitable catalyst for the reaction from the list of metals. Give a reason for your answer. aluminium calcium platinum potassium sodium suitable catalyst reason  
6. Chemical reactions  →  6.3. Reversible reactions and equilibrium
11. Organic chemistry  →  11.5. Alkenes
5. Chemical energetics  →  5.1. Exothermic and endothermic reactions
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5
Alcohols are a ‘family’ of organic molecules which have the same general formula. What is the name given to any ‘family’ of organic molecules which have the same general formula and similar chemical properties? Give the general formula of alcohols. Propan-1-ol can be made from propene. Name the reagent and give the conditions needed to convert propene into propan-1-ol. reagent conditions  Write a chemical equation for the complete combustion of propan-1-ol. A simple sugar can be represented as shown. O O H H Simple sugars can be polymerised to make more complex carbohydrates. Complete the diagram to show part of a carbohydrate polymer made from the simple sugar shown.  Name the chemical process which occurs when a carbohydrate polymer is broken down into simple sugars. What conditions are needed for this process to occur? Chromatography can be used to identify simple sugars in a mixture. A student analysed a mixture of simple sugars by chromatography. All the simple sugars in the mixture were colourless. What is the name given to the type of substance used to identify the positions of the simple sugars on the chromatogram? The student calculated the Rf value of a spot on the chromatogram. Complete the expression for the Rf value of the spot. Rf =  How could a student identify a simple sugar from its Rf value? Sometimes not all the substances in a mixture can be identified from the chromatogram produced. Explain why this may happen. 
11. Organic chemistry  →  11.2. Naming organic compounds
2. Atoms, elements and compounds  →  2.5. Simple molecules and covalent bonds
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