6.3. Reversible reactions and equilibrium
A subsection of Chemistry, 0620, through 6. Chemical reactions
Listing 10 of 390 questions
Chalcopyrite, FeCuS2, is used in the manufacture of sulfuricacid in the Contact process. In the first stage of the process, chalcopyrite reacts with oxygen in the air to produce sulfurdioxide, SO2, iron(oxide and copper(oxide. Complete the chemical equation for the reaction of FeCuS2 with oxygen. 4FeCuS2 + 13O2 → + +  Sulfurdioxide is then converted to sulfurtrioxide. 2SO2 + O2 2SO3 The reaction is exothermic. It is also an equilibrium. State two features of an equilibrium.  State the temperature and pressure used in this reaction. Include units. ● temperature ● pressure  Name the catalyst used. Explain why a catalyst is used. Describe and explain, in terms of equilibrium, what happens when the temperature is increased. Concentrated sulfuricacid is a dehydrating agent. When glucose is dehydrated, carbon and one other product are formed. Complete the equation to show the dehydration of glucose, C6H12O6. C6H12O6 → C +  
0620_w21_qp_41
THEORY
2021
Paper 4, Variant 1
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Table3.1 shows the average concentrations, in ng / 1000 cm3, of air pollutants in four different years. Table 3.1 year concentration of air pollutant in ng / 1000 cm3 ammonia hydrocarbons oxides of nitrogen particulates sulfur dioxide 10.6 12.0 15.3 30.1 20.5 11.2 13.0 21.6 28.2 20.0 14.3 15.2 23.5 26.5 25.0 15.5 9.0 14.0 25.2 18.2 Name the pollutant that has the lowest concentration in 2019. Name the pollutant that shows a continuous decrease in concentration from 2019 to 2022. Calculate the average mass, in ng, of sulfurdioxide in a 250 cm3 sample of polluted air in 2020.  mass = ng State one source of sulfurdioxide in the atmosphere. State one adverse effect of sulfur dioxide in the atmosphere. Choose the compound used to remove sulfur dioxide in flue gas desulfurisation. Tick (✓) one box. aluminium chloride calcium oxide methane sulfuric acid  Hydrochloricacid reacts with sodium sulfite. The products are sodium chloride, sulfur dioxide and a liquid which turns anhydrous cobalt(chloride pink. Complete the symbol equation for this reaction. Na2SO3 + HCl → 2NaCl + SO2 +  Name the acidified solution used to test for sulfurdioxide gas and state the observations. acidified solution observations  Ammonia forms an alkaline solution in water. Give the formula of the ion that is present in all alkaline solutions. Choose from the list the pH value for an alkaline solution. Draw a circle around your chosen answer. pH 1 pH 4 pH 7 pH 13 
0620_w23_qp_31
THEORY
2023
Paper 3, Variant 1
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Vanadium is a transition element. It has more than one oxidation state. The element and its compounds are often used as catalysts. Complete the electron distribution of vanadium by inserting one number. 2 + 8 + + 2 Predict three physical properties of vanadium which are typical of transition elements. 1. 2. 3. Vanadium(oxide is used to catalyse the exothermic reaction between sulfur dioxide and oxygen in the Contact Process. 2SO2 + O2 2SO3 The rate of this reaction can be increased either by using a catalyst or by increasing the temperature. Explain why a catalyst is used and not a higher temperature. The oxidation states of vanadium in its compounds are V(+5), V(+4), V(+3) and V(+2). The vanadium(ion can behave as a reductant or an oxidant. Indicate on the following equation which reactant is the oxidant. 2V3+ + Zn → 2V2+ + Zn2+ Which change in the following equation is oxidation? Explain your choice. V3+ + Fe3+ → V4+ + Fe2+
0620_s12_qp_31
THEORY
2012
Paper 3, Variant 1
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