6.3. Reversible reactions and equilibrium
A subsection of Chemistry, 0620, through 6. Chemical reactions
Listing 10 of 390 questions
Sulfuric acid is made industrially by a four-step process. step 1 Sulfur is burned in air to produce sulfurdioxide. step 2 Sulfur dioxide is converted into sulfurtrioxide. step 3 Sulfur trioxide is reacted with concentrated sulfuricacid to produce oleum. step 4 Oleum is reacted with water to produce concentrated sulfuricacid. Some sulfur is obtained by mining. Name one other major source of sulfur. What is the name of the process by which sulfuricacid is made industrially? Describe the conversion of sulfurdioxide into sulfurtrioxide in step2. In your answer, include: ● a chemical equation for the reaction ● the essential reaction conditions. When concentrated sulfuricacid is added to glucose, C6H12O6, a black solid is produced. The concentrated sulfuricacid acts as a dehydrating agent. What is removed from the glucose in this reaction? Name the black solid produced in this reaction. The gas hydrogensulfide, H2S, is produced when concentrated sulfuricacid is added to solid potassiumiodide. The reaction involves oxidation. Define the term oxidation in terms of electron transfer. Complete the dot-and-cross diagram to show the electron arrangement in a molecule of hydrogensulfide. Show outer shell electrons only. H H S Hydrogensulfide has a simple molecular structure. Explain why hydrogensulfide has a low boiling point. Dilute sulfuricacid reacts with aqueous sodiumhydrogencarbonate in a neutralisation reaction. H2SO4+ 2NaHCO3Na2SO4+ 2H2O+ 2CO2In a titration, 0.200 mol / dm3 aqueous sodium hydrogencarbonate was used to neutralise 20.0 cm3 of dilute sulfuricacid of concentration 0.150 mol / dm3. Calculate the number of moles of dilute sulfuricacid used in the titration. mol Calculate the number of moles of sodiumhydrogencarbonate needed to neutralise the dilute sulfuric acid. mol Calculate the volume, in cm3, of 0.200 mol / dm3 aqueous sodium hydrogencarbonate needed to neutralise the dilute sulfuricacid. cm3
0620_w18_qp_41
THEORY
2018
Paper 4, Variant 1
View
Sulfur is an important element. Explain how burning fossil fuels containing sulfur leads to the formation of acid rain. Sulfuricacid is manufactured by the Contact process. One step in the Contact process involves a reversible reaction in which sulfur trioxide, SO3, is formed. Write a chemical equation for this reversible reaction. Include the correct symbol to show that the reaction is reversible. State the conditions and name the catalyst used in this reversible reaction. temperature pressure catalyst  Describe how the sulfurtrioxide formed is converted into sulfuricacid in the next steps of the Contact process. Dilute sulfuricacid is used to make salts known as sulfates. A method consisting of three steps is used to make zincsulfate from zinccarbonate. step 1 Add an excess of zinccarbonate to 20 cm3 of 0.4 mol / dm3 dilute sulfuricacid until the reaction is complete. step 2 Filter the mixture. step 3 Heat the filtrate until a saturated solution forms and then allow it to crystallise. Name a suitable piece of apparatus for measuring 20 cm3 of dilute sulfuricacid in step1. State two observations which would show that the reaction is complete in step1.  Why is it important to add an excess of zinccarbonate in step1? What is meant by the term saturated solution in step3? The equation for the reaction is shown. ZnCO3+ H2SO4ZnSO4( ) + H2O+ CO2Complete the equation by inserting the state symbol for zincsulfate. Name another zinc compound which could be used to make zinc sulfate from dilute sulfuricacid using this method. Suggest why this method would not work to make bariumsulfate from bariumcarbonate and dilute sulfuricacid. In a titration, a student added 25.0 cm3 of 0.200 mol / dm3 aqueous sodium hydroxide to a conicalflask. The student then added a few drops of methylorange to the solution in the conicalflask. Dilute sulfuricacid was then added from a burette to the conical flask. The volume of dilute sulfuricacid needed to neutralise the aqueous sodiumhydroxide was 20.0 cm3. 2NaOH + H2SO4 Na2SO4 + 2H2O What was the colour of the methyl orange in the aqueous sodiumhydroxide? Determine the concentration of the dilute sulfuricacid in g / dm3. ● Calculate the number of moles of aqueous sodiumhydroxide added to the conical flask.  mol ● Calculate the number of moles of dilute sulfuricacid added from the burette.  mol ● Calculate the concentration of the dilute sulfuricacid in mol / dm3.  mol / dm3 ● Calculate the concentration of the dilute sulfuricacid in g / dm3.  g / dm3  Iron(sulfate decomposes when heated strongly. 2FeSO4Fe2O3+ SO2+ SO315.20 g of FeSO4was heated and formed 4.80 g of Fe2O3. [Mr, FeSO4 = 152; Mr, Fe2O3 = 160] Calculate the percentage yield for this reaction.  % 
0620_w18_qp_42
THEORY
2018
Paper 4, Variant 2
View
Sulfur exists as a number of different isotopes. What is meant by the term isotopes? A sulfide ion has the symbol shown. 34S 2– How many neutrons are contained in this sulfide ion? How is a sulfide ion, S2–, formed from a sulfur atom? Which element forms an ion with a 2+ charge that has the same number of electrons as a S2– ion? The manufacture of sulfuricacid by the Contact process occurs in four stages. stage 1 Molten sulfur is burned in air to produce sulfur dioxide gas. stage 2 Sulfurdioxide is reacted with oxygen to form sulfurtrioxide. stage 3 Sulfurtrioxide is combined with concentrated sulfuricacid to form oleum, H2S2O7. stage 4 Oleum is added to water to form sulfuricacid. Complete the chemical equation for stage1 by adding the appropriate state symbols. S( ) + O2( ) SO2( ) Name the catalyst used in stage2 and state the temperature used. catalyst temperature °C  Write chemical equations for the reactions in stage3 and stage4. stage3 stage4  Sulfurdioxide is a toxic gas. State one environmental reason why sulfur dioxide should not be released into the atmosphere. Describe the test for sulfurdioxide. test observations  Sulfurdioxide reacts with aqueous sodiumsulfite to produce a compound with the following composition by mass: 29.1% Na, 40.5% S and 30.4% O. Calculate the empirical formula of this compound.  empirical formula = 
0620_w19_qp_41
THEORY
2019
Paper 4, Variant 1
View
Questions Discovered
390