10.1. Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
A subsection of Chemistry, 9701, through 10. Group 2
Listing 10 of 275 questions
The Group IV oxides CO2 and SiO2 differ widely in their physical properties. Describe these differences and explain them in terms of their structure and bonding. What are the properties of a ceramic material? Why is silicon(oxide very suitable as a component of ceramics? Lead(oxide reacts with both acids and bases. What is the name given to oxides that have this property? Write a balanced equation for the reaction between PbO and NaOH. Tin forms an oxide, A, that contains the metal in both oxidation states II and IV. The formula of A can be found by the following method. • A sample of A was dissolved in H2SO4, producing solution B, which was a mixture of tin(sulfate and tin(sulfate. • A 25.0 cm3 sample of solution B was titrated with 0.0200 mol dm–3 KMnO4. 13.5 cm3 of KMnO4 was required to reach the end-point. • Another 25.0 cm3 sample of solution B was stirred with an excess of powdered zinc. This converted all the tin into tin(. The excess of zinc powder was filtered off and the filtrate was titrated with 0.0200 mol dm-3 KMnO4, as before. This time 20.3 cm3 of KMnO4 was required to reach the end-point. The equation for the reaction occurring during the titration is as follows. 2MnO4 – + 16H+ + 5Sn2+ 2Mn2+ + 8H2O + 5Sn4+ Write a balanced equation for the reaction between Zn and Sn4+. Use the Data Booklet to calculate the E o- values for the reactions between • Zn and Sn4+, • MnO4 – and Sn2+ Use the results of the two titrations to calculate • the number of moles of Sn2+ in the first titration sample, • the number of moles of Sn2+ in the second titration sample. Use the results of your calculation in to deduce the Sn2+/ Sn4+ ratio in the oxide A, and hence suggest the formula of A. A major use of tin is to make ‘tin plate’, which is composed of thin sheets of mild steel electroplated with tin, for use in the manufacture of food and drinks cans. A tin coating of 1.0 3 10–5 m thickness is often used. Calculate the volume of tin needed to coat a sheet of steel 1.0 m 3 1.0 m to this thickness, on one side only. Calculate the number of moles of tin that this volume represents. [The density of tin is 7.3 g cm–3.] The solution used for electroplating contains Sn2+ ions. Calculate the quantity of electricity in coulombs needed to deposit the amount of tin you calculated in .
9701_w09_qp_41
THEORY
2009
Paper 4, Variant 1
View
Describe and explain qualitatively the trend in the solubilities of the sulfates of the Group II elements. The major ore of barium is barytes, BaSO4. This is very unreactive, and so other barium compounds are usually made from the sulfide, BaS. This is obtained by heating the crushed ore with carbon, and extracting the BaS with water. BaSO4+ 4CBaS+ 4COWhen 250 g of ore was heated in the absence of air with an excess of carbon, it was found that the CO produced took up a volume of 140 dm3 at 450 K and 1 atm. Calculate the number of moles of CO produced. Calculate the number of moles of BaSO4 in the 250 g sample of the ore. Calculate the percentage by mass of BaSO4 in the ore. Use the following data and data from the Data Booklet to construct a Born-Haber cycle and calculate the lattice energy of BaS. standard enthalpy change of formation of BaS–460 kJ mol–1 standard enthalpy change of atomisation of Ba+180 kJ mol–1 standard enthalpy change of atomisation of S+279 kJ mol–1 electron affinity of the sulfur atom –200 kJ mol–1 electron affinity of the S– ion +640 kJ mol–1 lattice energy = kJ mol–1 Explain whether the magnitude of the lattice energy of BaS is likely to be greater or less than that of BaO.
9701_w09_qp_42
THEORY
2009
Paper 4, Variant 2
View
The element magnesium, Mg, proton number 12, is a metal which is used in many alloys which are strong and light. Magnesium has several naturally occurring isotopes. What is meant by the term isotope? Complete the table below for two of the isotopes of magnesium. isotope number of protons number of neutrons number of electrons 24Mg 26Mg A sample of magnesium had the following isotopic composition: 24Mg, 78.60%; 25Mg, 10.11%; 26Mg, 11.29%. Calculate the relative atomic mass, Ar, of magnesium in the sample. Express your answer to an appropriate number of significant figures. Antimony, Sb, proton number 51, is another element which is used in alloys. Magnesium and antimony each react when heated separately in chlorine. Construct a balanced equation for the reaction between magnesium and chlorine. When a 2.45 g sample of antimony was heated in chlorine under suitable conditions, 4.57 g of a chloride A were formed. Calculate the amount, in moles, of antimony atoms that reacted. Calculate the amount, in moles, of chlorine atoms that reacted. Use your answers to and to determine the empirical formula of A. The empirical and molecular formulae of A are the same. Construct a balanced equation for the reaction between antimony and chlorine. The chloride A melts at 73.4 °C while magnesium chloride melts at 714 °C. What type of bonding is present in magnesium chloride? Suggest what type of bonding is present in A.
9701_w10_qp_23
THEORY
2010
Paper 2, Variant 3
View
The most typical oxides of tin and lead are SnO, SnO2, PbO and PbO2. The following two generalisations can be made about the oxides of the elements in Group IV. • As the metallic character of the elements increases down the Group, the oxides become more basic. • The oxides of the elements in their higher oxidation states are more acidic than the oxides of the elements in their lower oxidation states. Use these generalisations to suggest which of the above oxides of tin or lead is most likely to react with each of the following reagents. In each case write a balanced equation for the reaction. with NaOHformula of oxide equation with HClformula of oxide equation ‘Red lead’ is used as a pigment, and as a metal primer paint to prevent the corrosion of steel. It is an oxide of lead that contains 9.30% oxygen by mass. Calculate to 3 significant figures the number of moles of oxygen and lead contained in a 100.0 g sample of red lead. Hence calculate its empirical formula. empirical formula: Lead(chloride is slightly soluble in water. PbCl2Pb2++ 2Cl–Ksp = 2.0 × 10–5 Write an expression for the solubility product, Ksp for lead(chloride and state its units. Ksp = units Calculate [Pb2+] in a saturated solution of PbCl2. An excess of PbCl2is stirred with 0.50 mol dm–3 NaCl until equilibrium has been established. The excess PbCl2is then filtered off. Assuming [Cl–] remains at 0.50 mol dm–3 throughout, calculate the [Pb2+] in the remaining solution. Suggest an explanation for the difference between this value and the value that you calculated in .
9701_w10_qp_41
THEORY
2010
Paper 4, Variant 1
View
The most typical oxides of tin and lead are SnO, SnO2, PbO and PbO2. The following two generalisations can be made about the oxides of the elements in Group IV. • As the metallic character of the elements increases down the Group, the oxides become more basic. • The oxides of the elements in their higher oxidation states are more acidic than the oxides of the elements in their lower oxidation states. Use these generalisations to suggest which of the above oxides of tin or lead is most likely to react with each of the following reagents. In each case write a balanced equation for the reaction. with NaOHformula of oxide equation with HClformula of oxide equation ‘Red lead’ is used as a pigment, and as a metal primer paint to prevent the corrosion of steel. It is an oxide of lead that contains 9.30% oxygen by mass. Calculate to 3 significant figures the number of moles of oxygen and lead contained in a 100.0 g sample of red lead. Hence calculate its empirical formula. empirical formula: Lead(chloride is slightly soluble in water. PbCl2Pb2++ 2Cl–Ksp = 2.0 × 10–5 Write an expression for the solubility product, Ksp for lead(chloride and state its units. Ksp = units Calculate [Pb2+] in a saturated solution of PbCl2. An excess of PbCl2is stirred with 0.50 mol dm–3 NaCl until equilibrium has been established. The excess PbCl2is then filtered off. Assuming [Cl–] remains at 0.50 mol dm–3 throughout, calculate the [Pb2+] in the remaining solution. Suggest an explanation for the difference between this value and the value that you calculated in .
9701_w10_qp_42
THEORY
2010
Paper 4, Variant 2
View
Explain why complexes of transition elements are often coloured. When water is added to white anhydrous CuSO4, the solid dissolves to give a blue solution. The solution changes to a yellow-green colour when concentrated NH4Cl is added to it. Concentrating the solution produces green crystals of an ammonium salt with the empirical formula CuN2H8Cl4. Explain these observations, showing your reasoning. Copper can be recovered from low-grade ores by ‘leaching’ the ore with dilute H2SO4, which converts the copper compounds in the ore into CuSO4. The concentration of copper in the leach solution can be estimated by adding an excess of aqueous potassium iodide, and titrating the iodine produced with standard Na2S2O3. 2Cu2+ + 4I– 2CuI + I2 I2 + 2S2O3 2– 2I– + S4O6 2– When an excess of KIwas added to a 50.0 cm3 sample of leach solution, and the resulting mixture titrated, 19.5 cm3 of 0.0200 mol dm–3 Na2S2O3were required to discharge the iodine colour. Calculate the [Cu2+], and hence the percentage by mass of copper, in the leach solution. percentage of copper = %
9701_w10_qp_43
THEORY
2010
Paper 4, Variant 3
View
Questions Discovered
275