10. Group 2
A section of Chemistry, 9701
Listing 10 of 275 questions
The Group 2 elements Mg to Ba are all silvery‑white reactive metals. Draw a labelled diagram to show the bonding and structure of the Group 2 metals at room temperature. Explain why Mg has a higher electrical conductivity than Na. Write an equation for the reaction of magnesium with cold water. Identify a single reagent that can be used to distinguish separate samples of dilute Mg(NO3)2and dilute Ba(NO3)2. Explain your answer. reagent explanation Describe what is observed when SrI2reacts with concentrated sulfuric acid. Compound X, an anhydrous Group 2 bromide, is dissolved in water and titrated against aqueous silver nitrate. A solution containing 0.250 g of X requires 33.65 cm3 of 0.0500 mol dm–3 AgNO3for complete reaction. Identify X. Show your working. X =
9701_m23_qp_22
THEORY
2023
Paper 2, Variant 2
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The most common zinc mineral contains zinc(sulfide, ZnS. Complete the electrons in boxes diagram in to show the electronic configuration of a zinc(ion. 3d 4s 4p Complete to show the Born–Haber diagram for the ionic solid ZnS. Include state symbols of relevant species. Zn2++ S+ 2e– ZnSZn2++ S–+ e– Zn2++ S2–IE2 IE1 ΔHf ΔHlatt ΔHat(S) EA2 EA1 ΔHat(Zn) Describe the trend in the first electron affinity of the Group 16 elements S to Te. Explain your answer. Explain why the lattice energy, ∆Hlatt, of ZnO is more exothermic than that of ZnS. Zinc metal can be obtained in a two-step process as shown. step 1 2ZnS+ 3O22ZnO+ 2SO2step 2 ZnO+ CZn+ COThe reactions are carried out at 800 °C. Predict the sign of the entropy change, ∆S o , of the reaction in step 1. Explain your answer. Use the data in Table 1.1 to calculate ∆S o of the reaction shown in step 2. Table 1.1 chemical ZnOCZnCOS o / J K–1 mol–1 43.7 5.7 50.8 197.7 ∆S o = J K–1 mol–1 An equation for the direct reduction of ZnS by carbon is shown. 2ZnS+ C2Zn+ CS2∆H o = +733 kJ mol–1 ∆S o = +218 J K–1 mol–1 This reaction is not feasible at 800 °C. Calculate ∆G o for this reaction at 800 °C. ∆G o = kJ mol–1 Zn(NO3)2 undergoes thermal decomposition when heated. The reaction is similar to the thermal decomposition of Group 2 nitrates. Construct an equation for the thermal decomposition of Zn(NO3)2. The radii of some Group 2 cations and Zn2+ are shown in Table 1.2. Table 1.2 cation Mg2+ Ca2+ Sr2+ Ba2+ Zn2+ radius / pm State and explain the trend in thermal stability of the Group 2 nitrates down the group. Use Table 1.2 to suggest which Group 2 nitrates are less thermally stable than zinc nitrate.
9701_m23_qp_42
THEORY
2023
Paper 4, Variant 2
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Bismuth is an element in Group 15 of the Periodic Table. Bismuth has metallic bonding. Draw a labelled diagram to show the metallic bonding in bismuth. Bismuth reduces water to form bismuth oxide, Bi2O3. A colourless gas that ignites with a squeaky pop also forms. Construct an equation for the reduction of water by bismuth. Bi2O3 is a yellow insoluble solid that melts at 1090 K. The molten compound conducts electricity. Deduce the structure and bonding of Bi2O3. Explain your answer. Bi2O3 can be used to form NaBiO3, as shown in equation 1. equation 1 Na2O + Bi2O3 + O2 2NaBiO3 Deduce the oxidation number of Bi in Bi2O3 and in NaBiO3. oxidation number of Bi: in Bi2O3 in NaBiO3 Identify the reducing agent in equation 1. NaBiO3 is an oxidising agent with similar properties to KMnO4. shows an example of the use of NaBiO3 as an oxidising agent. OH OH NaBiO3 O O H + X Y Z Explain the term oxidising agent. Compound X forms when methylbut-2-ene reacts with KMnO4. State the essential conditions for this reaction. Complete Table 1.1 to show what is observed when compounds Y and Z react separately with the named reagents. Table 1.1 reagent observation with Y observation with Z Na2CO3no reaction alkaline I22,4-dinitrophenylhydrazine (2,4-DNPH) Tollens’ reagent Construct an equation for the reaction of Z with NaBH4. Use to represent an atom of hydrogen from the reducing agent. NaBiO3 can be used to determine the concentration of Mn2+. The ionic equation for the reaction is shown in equation 2. equation 2 2Mn2+ + 5BiO3 – + 14H+ 2MnO4 – + 5Bi3+ + 7H2O A student uses the following procedure in an experiment. • Add 100.0 cm3 of a saturated solution of Mn2+to a volumetric flask. • Add distilled water to the flask to make a 1.00 dm3 diluted solution. • Titrate a 25.00 cm3 sample of the diluted solution with 0.100 mol dm–3 NaBiO3. The 25.00 cm3 sample of the diluted solution of Mn2+reacts completely with exactly 21.50 cm3 of 0.100 mol dm–3 NaBiO3. Calculate the concentration, in mol dm–3, of Mn2+in the saturated solution. Show your working. concentration of Mn2+in the saturated solution = mol dm–3
9701_m24_qp_22
THEORY
2024
Paper 2, Variant 2
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Magnesium is the eighth most common element in the Earth’s crust. The metal is widely used in alloys which are light and strong. Some reactions of magnesium and its compounds are shown in the reaction scheme below. Identify, by name or formula, compounds A to F. A B C D E F H2+ ACdil. H2SO4 Na2CO3heat in air heat NaOHdil. HNO3 heat MgDFdil. HCl heat evaporate BEF+ H2Construct balanced equations for the following reactions. magnesium to compound A compound C to compound D compound F to compound D Suggest a balanced equation for the effect of heat on compound E.
9701_s05_qp_2
THEORY
2005
Paper 2, Variant 0
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Monuments made of marble or limestone, such as the Taj Mahal in India and the Mayan temples in Mexico, are suffering erosion by acid rain. The carbonate stone is converted by the acid rain into the relatively more soluble sulphate. CaCO3+ H2SO4→CaSO4+ H2O+ CO2acid rain Write an expression for the solubility product, Ksp, of CaSO4, stating its units. The Ksp of CaSO4 has a numerical value of 3 x 10–5. Use your expression in to calculate in a saturated solution. Hence calculate the maximum loss in mass of a small statue if 100 dm3 of acid rain falls on it. Assume the statue is made of pure calcium carbonate, and that the acid rain becomes saturated with CaSO4. The life of such monuments is now being extended by treating them with a mixture of urea and barium hydroxide solutions. After soaking into the pores of the carbonate rock, the urea gradually decomposes to ammonia and carbon dioxide. The carbon dioxide then reacts with the barium hydroxide to form barium carbonate. (NH2)2CO+ H2O⎯→ 2NH3+ CO2Ba(OH)2+ CO2⎯→ BaCO3+ H2OAcid rain then converts the barium carbonate to its sulphate. BaCO3+ H2SO4⎯→ BaSO4+ H2O+ CO2Barium sulphate is much less soluble than calcium sulphate. A saturated solution contains [Ba2+] = 9.0 x 10–6mol dm–3. Explain why barium sulphate is less soluble than calcium sulphate. Use [T Write an expression for the Ksp of barium sulphate and use the data to calculate its value. Explain what is meant by the term lattice energy. Predict, with a reason, how the lattice energy of BaSO4 might compare with that of MgSO4.
9701_s06_qp_4
THEORY
2006
Paper 4, Variant 0
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Questions Discovered
275