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CIE Nov 2017 v3 Paper 4 Q2
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![(a) The table lists values of solubility products, Ksp, of some Group 2 carbonates. PMT solubility product in water at 298 K, Ksp / mol2 dm6 MgCO3 CaCO3 SrCO3 1.0105 5.0109 1.11010 Use the data in the table to describe the trend in the solubility of the Group 2 carbonates down the group.[1] (b) (i) Write an equation to show the equilibrium for the solubility product for MgCO3. Include state symbols.[1] (ii) With reference to your equation in (i), suggest what is observed when a few cm3 of concentrated Na2CO3(aq) are added to a saturated solution of MgCO3. Explain your answer.[2] (c) Use the data in the table to calculate the solubility of MgCO3 in water at 298 K, in g dm3. solubility of MgCO3 =g dm3 [2]UCLES 2017 9701/43/O/N/17<br />
PMT (d) (i) Magnesium nitrate decomposes at a lower temperature than barium nitrate. Explain why.[2] (ii) A sample of barium nitrate was heated strongly until no further change occurred. A white solid was formed. Write an equation for the action of heat on barium nitrate.[1] (iii) When water was added to the white solid produced in (d)(ii), an alkaline solution was produced. Adding sulfuric acid to this solution produced a white precipitate. Write equations to explain these observations.[2] [Total: 11]UCLES 2017 9701/43/O/N/17 [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/November_2017_v3_QP_-_Paper_4_CIE_Chemistry_A-level_2-0.jpg)
![9701/43 Question 1(d) m = 2 and n = 0 Cambridge International AS/A LevelMark Scheme PUBLISHED Answer PMT October/November 2017 Marks 1 Question 2(a) 2(b)(i) it / solubility decreases down the group and Ksp decreases MgCO3(s)Mg2+(aq) + CO3 2(aq) Answer 2(b)(ii) (white) solid appears / precipitation (of MgCO3) as [CO3 2] increases shifting equilibrium to the LHS (precipitating out MgCO3) 2(c) 2(d)(i) 2(d)(ii) 2(d)(iii) mol dm3 solubility = 1.010-5 = 3.16103 solubility= 3.210384.3 = 0.27 g dm3 Mg2+ ion is smaller than Ba2+ ion or ionic radii increase down group ora (Mg2+) distorts / polarises / the anion / nitrate group / nitrate ion / NO3 (1) / NO3 ion more easily (than Ba2+) ora Ba(NO3)2BaO + 2NO2 + O2 BaO + H2OBa(OH)2 Ba(OH)2 + H2SO4BaSO4 + 2H2O Marks 1 1 1 1 1 1 1 1 1 1 1UCLES 2017 Page 3 of 13<br />](https://learnah.org/wp-content/uploads/2018/08/November_2017_v3_MS_-_Paper_4_CIE_Chemistry_A-level_2.jpg)