10. Group 2
A section of Chemistry, 9701
Listing 10 of 275 questions
Nanotechnology is a fast-developing area of science based on the ability to manipulate materials of very small dimensions. On the scale shown in metres, mark the upper and lower limits of the range of sizes for nanoparticles. 10–6 10–7 10–8 10–9 10–10 10–11 10–12 One of the most commonly recognised nanoparticles is the ‘buckyball’, a spherical form of carbon containing 60 carbon atoms. It has been referred to as the third allotrope of carbon. Diamond and graphite are two other allotropes of carbon. Suggest what is meant by the term allotrope. Nanoparticles are used to deliver drugs within cells. Suggest what property of nanoparticles enables them to be used in this way. Explain your answer. Copper is an important metal that has been used for thousands of years. The problem today is that most of the ores rich in copper compounds have been used up. A century ago ores containing >2% of copper by mass would have been worked; today’s mines have to operate at much lower percentages, down to 0.5% of copper by mass. By what type of reaction is the copper present in the ore converted to copper metal? One of the main ores of copper contains the mineral chalcopyrite, CuFeS2. Calculate the percentage of copper by mass in chalcopyrite. If the ore contains 2% of chalcopyrite by mass, calculate the mass of copper which can be produced from each tonne of ore. Certain bacteria are able to extract copper from the ‘spoil’ heaps of previously mined copper ore. These bacteria are sprayed onto the spoil heaps in an aqueous solution and the resulting solution containing iron(sulfate and copper(sulfate is collected in tanks. Suggest how the copper could be recovered as metal.
9701_s11_qp_42
THEORY
2011
Paper 4, Variant 2
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Nanotechnology is a fast-developing area of science based on the ability to manipulate materials of very small dimensions. On the scale shown in metres, mark the upper and lower limits of the range of sizes for nanoparticles. 10–6 10–7 10–8 10–9 10–10 10–11 10–12 One of the most commonly recognised nanoparticles is the ‘buckyball’, a spherical form of carbon containing 60 carbon atoms. It has been referred to as the third allotrope of carbon. Diamond and graphite are two other allotropes of carbon. Suggest what is meant by the term allotrope. Nanoparticles are used to deliver drugs within cells. Suggest what property of nanoparticles enables them to be used in this way. Explain your answer. Copper is an important metal that has been used for thousands of years. The problem today is that most of the ores rich in copper compounds have been used up. A century ago ores containing >2% of copper by mass would have been worked; today’s mines have to operate at much lower percentages, down to 0.5% of copper by mass. By what type of reaction is the copper present in the ore converted to copper metal? One of the main ores of copper contains the mineral chalcopyrite, CuFeS2. Calculate the percentage of copper by mass in chalcopyrite. If the ore contains 2% of chalcopyrite by mass, calculate the mass of copper which can be produced from each tonne of ore. Certain bacteria are able to extract copper from the ‘spoil’ heaps of previously mined copper ore. These bacteria are sprayed onto the spoil heaps in an aqueous solution and the resulting solution containing iron(sulfate and copper(sulfate is collected in tanks. Suggest how the copper could be recovered as metal.
9701_s11_qp_43
THEORY
2011
Paper 4, Variant 3
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Silver bromide, AgBr, is widely used in photography. In a photographic film, AgBr crystals are precipitated into a gelatine base as ‘grains’ of diameter about 1 × 10–6m. Calculate the approximate number of silver ions contained in a grain of AgBr of mass 2.5 × 10–12g. AgBr is only sparingly soluble in water. The [Ag+] in a saturated solution of AgBr can be estimated by measuring the Ecell of the following cell. In the spaces below, identify what the four letters A – D in the above diagram represent. A C B D Predict how the potential of the right hand electrode might vary as [Ag+] is decreased. In its saturated solution, = 7.1 × 10–7mol dm–3. Write an expression for the solubility product of AgBr, and calculate its value, including units. salt bridge H2, 1 atm, 298 K [Ag+] = x mol dm–3 A B C D Use Write a chemical equation representing the lattice energy of AgBr. Use the following data to calculate a value for the lattice energy of AgBr. first ionisation energy of silver = +731 kJ mol–1 electron affinity of bromine = –325 kJ mol–1 enthalpy change of atomisation of silver = +285 kJ mol–1 enthalpy change of atomisation of bromine = +112 kJ mol–1 enthalpy change of formation of AgBr= –100 kJ mol–1 How might the lattice energy of AgCl compare to that of AgBr? Explain your answer. In photography a bromide ion absorbs a photon and releases an electron which reduces a silver ion to a silver atom. Br– →Br + e– Ag+ + e– →Ag Predict whether it would require more energy or less energy to initiate this process in a AgCl emulsion, compared to a AgBr emulsion. Explain your answer. Examiner’s Use
9701_w05_qp_4
THEORY
2005
Paper 4, Variant 0
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