6. Chemical reactions
A section of Chemistry, 0620
Listing 10 of 905 questions
The diagram shows the changes of state when sulfur is heated. solid sulfur A liquid sulfur sulfur vapour B Give the names of the changes of state labelled A and B. A B Describe the arrangement and motion of the particles in sulfur vapour. arrangement motion Give one use of sulfur. Some compounds of sulfur are found in coal. Explain why the presence of sulfur in coal has an adverse effect on human health when the coal is burnt. One of the compounds of sulfur in coal is thiophene. The structure of thiophene is shown. C C C C S H H H H Determine the formula of thiophene. Thiophene can be made in the laboratory by heating ethyne, C2H2, with hydrogen sulfide, H2S, in the presence of a catalyst. What is the purpose of the catalyst? When 2.6 g of ethyne react with excess hydrogen sulfide, 4.2 g of thiophene are formed. Calculate the mass of thiophene formed when 15.6 g of ethyne react with excess hydrogen sulfide.
0620_w16_qp_31
THEORY
2016
Paper 3, Variant 1
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Sulfuric acid can be manufactured from the raw materials sulfur, air and water. The process can be divided into four stages. stage 1 converting sulfur into sulfur dioxide stage 2 converting sulfur dioxide into sulfur trioxide stage 3 converting sulfur trioxide into oleum, H2S2O7 stage 4 converting oleum into sulfuric acid stage 1 Describe how sulfur is converted into sulfur dioxide. Write a chemical equation for the conversion of sulfur into sulfur dioxide. stage 2 Sulfur dioxide is converted into sulfur trioxide according to the following equation. 2SO2 + O2 2SO3 The reaction is carried out at a temperature of 450 °C and a pressure of 1–2atmospheres using a catalyst. The energy change, ∆H, for the reaction is –196 kJ / mol. What is the meaning of the symbol ? Name the catalyst used in this reaction. Why is a catalyst used? If a temperature higher than 450 °C were used, what would happen to the amount of sulfurtrioxide produced? Give a reason for your answer. Suggest a reason why a temperature lower than 450 °C is not used. If a pressure higher than 1–2 atmospheres were used, what would happen to the amount of sulfur trioxide produced? Give a reason for your answer. stage 3 What is added to sulfur trioxide to convert it into oleum? Write a chemical equation for the conversion of sulfur trioxide into oleum. stage 4 What is added to oleum to convert it into sulfuric acid? Write a chemical equation for the conversion of oleum into sulfuric acid. Give one use of sulfuric acid. Sulfuric acid reacts with a hydrocarbon called benzene to produce benzenesulfonic acid, C6H5SO3H. Benzenesulfonic acid is a strong acid which ionises to produce hydrogen ions, H+, and benzenesulfonate ions, C6H5SO3 –. What is meant by the term strong acid? Describe how to show that a 1 mol / dm3 solution of benzenesulfonic acid is a strong acid. Write a chemical equation for the reaction between benzenesulfonic acid and sodiumcarbonate, Na2CO3.
0620_w16_qp_43
THEORY
2016
Paper 4, Variant 3
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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
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