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CIE Jun 2016 v3 Paper 4 Q1
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![Answer all the questions in the spaces provided. PMT (a) Limewater is a saturated solution of Ca(OH)2 in water. It is used to test for the presence of CO2 in a gaseous mixture. (i) Write an equation for the reaction between limewater and CO2.[1] A saturated solution of Ba(OH)2 can be used instead of Ca(OH)2 to test for CO2. A saturated solution of Mg(OH)2 cannot be used for this test. (ii) Explain why a saturated solution of Ba(OH)2 can be used to test for CO2.[1] (iii) Explain why a saturated solution of Mg(OH)2 cannot be used to test for CO2.[2] (b) Describe and explain the trend in the thermal stabilities of the carbonates down Group 2.[3] (c) Nickel carbonate, NiCO3, decomposes on heating. Use the Data Booklet to explain whether NiCO3 will decompose more or less readily than CaCO3.[2] [Total: 9]UCLES 2016 9701/43/M/J/16<br />](https://learnah.org/wp-content/uploads/2018/08/June_2016_v3_QP_-_Paper_4_CIE_Chemistry_A-level_1.jpg)
![Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A LevelMay/June 2016 9701 43 PMT Answer Marks [1] [1] [1] [1] [1] [1] [1] [1] [1] [Total: 9] [1] [1] [1] [1] [1] [1] Question (a) (i) Ca(OH)2 + CO2CaCO3 + H2O (ii) Ba(OH)2 is soluble, OR BaCO3 is insoluble (iii) Mg(OH)2 is insoluble / not very soluble will not form ppt. of MgCO3 (b) carbonates are more stable down the group due to increase in cationic size / radius (causing) less polarisation of CO3 2 ion (c) radius of Ni 2+ = 0.070 nm; radius of Ca 2+ = 0.099 nm so NiCO3 decomposes more readily than CaCO3 (a) (i) Co: 3s 3p 3d 4s Co 2+ 3s 3p 3d (ii) solution starts pink turns blue pink is [Co(H2O)6] blue is [CoCl 2 4] 2+ this complex is tetrahedralCambridge International Examinations 2016<br />](https://learnah.org/wp-content/uploads/2018/08/June_2016_v3_MS_-_Paper_4_CIE_Chemistry_A-level_1.jpg)
