11.4. The reactions of chlorine
A subsection of Chemistry, 9701, through 11. Group 17
Listing 10 of 290 questions
Use Potassium manganate(can be used to estimate the percentage of hydrogen peroxide in household bleach. The following unbalanced equation represents the reaction between them. MnO– 4 + H2O2 + H+ Mn2+ + H2O + O2 Balance this equation by putting the appropriate numbers in the spaces above. Use data from the Data Booklet to calculate the E o cell for the reaction. When 0.020 mol dm–3 KMnO4was added from a burette into an acidified 25.0 cm3 sample of H2O2, 15.0 cm3 of KMnO4 was required to reach the end-point. Describe what you would see during this titration, and also at the end-point. Calculate the concentration of H2O2 in the sample.
9701_w07_qp_4
THEORY
2007
Paper 4, Variant 0
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Use 10 Read the following article about the use of bacteria in mining, and then answer the questions that follow it. The discovery that bacteria could ʻmineʼ metals for us was made in Spain. The Rio Tinto mine, in the southwest corner of Spain, was originally mined for copper by the Romans some 2,000 years ago. In 1752, some mining engineers looked over the mine to see if it could possibly be re-opened. They noticed streams of a blue-green liquid running from spoil heaps of the processed rock that lay around the mine. When this blue-green liquid ran over iron, it coated the iron with a brown film. The brown film was metallic copper. There was still some copper left in the spoil heaps. At the time, everybody thought that the copper was being dissolved in the liquid through a simple chemical reaction. But in 1947, US scientists discovered that the copper was being ʻminedʼ by a bacterium called Thiobacillus ferrooxidans. The bacterium Thiobacillus ferrooxidans lives off the chemical energy trapped in metal sulphides. In the ore, the copper exists as copper sulphide. The bacteria gain energy by converting the copper sulphide to copper sulphate, which is then excreted. At the same time, they absorb the difference in energy in the chemical bonds. These bacteria can also obtain energy in similar reactions with ores of zinc, lead and uranium. Use the Data Booklet to explain why the blue-green liquid coated the iron with copper. Write an equation for the reaction. Suggest two reasons why this method of extracting copper might be useful for ore containing only a small percentage of copper. Suggest one disadvantage of using bacteria rather than traditional mining and smelting methods. Examiner’s Use In conventional copper mining, the ore will typically contain 0.5 – 2.0% copper, which gives an idea of what a valuable resource copper is. The ore from a particular mine contains 0.75% copper, and 150 000 tonnes of ore are mined each year. From this ore about 60% of the copper is extracted, and the remainder is left in the ‘spoil heaps’ of processed ore. What mass of copper is extracted each year? If the use of bacteria can recover a further 17% of copper from the spoil heaps, what is the extra mass of copper produced? Suggest why bacteria are unlikely to be used in the extraction of aluminium. Metals like copper and zinc from abandoned mines can contaminate ground-water. Suggest one way of removing these contaminants.
9701_w07_qp_4
THEORY
2007
Paper 4, Variant 0
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11 One of the greatest challenges facing scientists today is the development of effective drugs to treat different forms of cancer. Drugs can be introduced into the body by injection or by mouth. Taking drugs by injection avoids the drug being broken down in the digestive system. State two other advantages of giving drugs by injection. The drug Ultiva has been developed to treat ovarian cancer, and is usually given by injection. H3C OCH3 OCH3 O O O N N Ultiva Study the structure of Ultiva and draw a circle around two different functional groups that could be broken down in the digestive system. One way of avoiding the breakdown of drugs in the body is to use a specially designed nanoparticle which encloses the drug. If the nanoparticles are made of a particular sort of polymer, they absorb water at the slightly acidic pH inside some cells, increasing their diameter from around 100 nm to around 1000 nm. This spreads out the polymer chains allowing release of the drug. Other than absorbing water, suggest a property this polymer would need to possess for its use in drug delivery. Why would this method of release not work if the nanoparticles were taken by mouth? Polymers may be formed by two different types of chemical reaction. Name the two types of reaction and write an equation to illustrate each reaction type. name equation name equation The breakdown of polymers, such as carbohydrates and proteins in the body is important for digestion. What type of reaction is generally involved?
9701_w10_qp_43
THEORY
2010
Paper 4, Variant 3
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Oseltamivir is an antiviral drug that slows the spread of the infl uenza (fl u) virus. O HN O O O NH2 oseltamivir Circle two bonds, each in a different functional group, that could be easily hydrolysed in the body. Oseltamivir is a chiral drug. This drug is usually taken as a single optical isomer rather than as a mixture of isomers. Suggest one benefi t of taking a drug in this way. Oseltamivir is a competitive inhibitor of an enzyme produced by the fl u virus. Explain the meaning of the term competitive inhibitor and state how its action could be overcome. ATP plays an important role in metabolic reactions in living organisms. NH2 N N N CH2O P H H N H O HO H OH O P O P O– O– O– O O O O– ATP What is the function of ATP in living organisms?
9701_w14_qp_41
THEORY
2014
Paper 4, Variant 1
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Oseltamivir is an antiviral drug that slows the spread of the infl uenza (fl u) virus. O HN O O O NH2 oseltamivir Circle two bonds, each in a different functional group, that could be easily hydrolysed in the body. Oseltamivir is a chiral drug. This drug is usually taken as a single optical isomer rather than as a mixture of isomers. Suggest one benefi t of taking a drug in this way. Oseltamivir is a competitive inhibitor of an enzyme produced by the fl u virus. Explain the meaning of the term competitive inhibitor and state how its action could be overcome. ATP plays an important role in metabolic reactions in living organisms. NH2 N N N CH2O P H H N H O HO H OH O P O P O– O– O– O O O O– ATP What is the function of ATP in living organisms?
9701_w14_qp_42
THEORY
2014
Paper 4, Variant 2
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Solution Y is hydrochloric acid, HCl . Solution Z is aqueous 4-chlorobutanoic acid, Cl (CH2)3CO2H. The pKa of Cl (CH2)3CO2His 4.52. The pH of both solutions is 4.00. Write an expression for the Ka of Cl (CH2)3CO2H. Ka =  Write a mathematical expression to describe the relationship between Ka and pKa. Calculate [H+] in solutions Y and Z.  [H+] = mol dm–3 Calculate the ratio dissolved in solution Y [Cl (CH2)3CO2H] dissolved in solution Z .  dissolved in solution Y [Cl (CH2)3CO2H] dissolved in solution Z = A buffer solution of pH5.00 is produced by adding sodiumpropanoate to 5.00 g of propanoicacid in 100 cm3 of distilledwater. Calculate the mass of sodiumpropanoate that must be used to produce this buffer solution. The Ka of propanoicacid is 1.35 × 10–5 mol dm–3. [Mr: propanoic acid, 74.0; sodium propanoate, 96.0]  mass of sodium propanoate = g Some dilute sulfuricacid is mixed with a small sample of the buffer solution described in . The final pH of the mixture is close to 1. Explain this observation.
9701_w21_qp_41
THEORY
2021
Paper 4, Variant 1
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Solution Y is hydrochloric acid, HCl . Solution Z is aqueous 4-chlorobutanoic acid, Cl (CH2)3CO2H. The pKa of Cl (CH2)3CO2His 4.52. The pH of both solutions is 4.00. Write an expression for the Ka of Cl (CH2)3CO2H. Ka =  Write a mathematical expression to describe the relationship between Ka and pKa. Calculate [H+] in solutions Y and Z.  [H+] = mol dm–3 Calculate the ratio dissolved in solution Y [Cl (CH2)3CO2H] dissolved in solution Z .  dissolved in solution Y [Cl (CH2)3CO2H] dissolved in solution Z = A buffer solution of pH5.00 is produced by adding sodiumpropanoate to 5.00 g of propanoicacid in 100 cm3 of distilledwater. Calculate the mass of sodiumpropanoate that must be used to produce this buffer solution. The Ka of propanoicacid is 1.35 × 10–5 mol dm–3. [Mr: propanoic acid, 74.0; sodium propanoate, 96.0]  mass of sodium propanoate = g Some dilute sulfuricacid is mixed with a small sample of the buffer solution described in . The final pH of the mixture is close to 1. Explain this observation.
9701_w21_qp_43
THEORY
2021
Paper 4, Variant 3
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