Chemical bonding - student copy

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Nov 24, 2024

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YISHUN INNOVA JUNIOR COLLEGE 2021 JC2 H2 CHEMISTRY CHEMICAL BONDING (FOUNDATION) NYJC/2020/I/3 1 In which pair do the species have different shapes from each other? A BeCl 2 and CO 2 B BH 4 and NH 4 + C OF 2 and SCl 2 D PH 3 and SO 3 NYJC/2020/I/4 2 Liquids X and Y do not react with one another. They have identical boiling points. When a particular volume of X is shaken with a similar volume of Y , they form a liquid mixture Z . The average intermolecular forces in liquid Z are stronger than the average of the forces in X and the forces in Y . Which deductions from this information are correct? 1 The mixing of X and Y is exothermic. 2 The vapour pressure of liquid Z will be less than that of either liquid X or liquid Y at the same temperature. 3 The boiling point of liquid Z will be lower than that of either liquid X or liquid Y at the same pressure. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only SAJC/2020/I/5 3 Which species contain a dative (co-ordinate) bond?
1 CO 2 CO 3 2− 3 N 2 H 4 4 N 2 O 4 A 2, 3 and 4 B 1 and 2 only C 1 and 4 only D 3 and 4 only SAJC/2020/I/18 4 Which bond angles are present in sulfonamide? 1 105° 2 107° 3 109.5° 4 120° A 2, 3 and 4 B 2 and 3 only
C 1 and 3 only D 1 only TJC/2020/I/7 5 Which of the following cannot be explained by hydrogen bonding? A The difference in the boiling points between water and ammonia. B The difference in volatility between pentan-2-ol and octan-2-ol. C The difference in boiling point between 2-nitrophenol and 4-nitrophenol. D The difference in the relative molecular mass of ethanoic acid molecules in benzene and in water. NYJC/2020/I/4 6 Element E has a high melting point of 1287 °C and conducts electricity. The chloride of E has a melting point of 399 o C, does not conduct electricity in solid or liquid state, and is soluble in benzene. Which of the following could be element E ? A Beryllium B Carbon C Copper D Lithium ACJC/2020/II/1c 7 (c) A diagonal relationship is said to exist between certain pairs of diagonally adjacent elements in the second and third Periods. The elements and their compounds in these pairs are observed to share similar properties. An example of such a pair is beryllium and aluminium. (i) Draw the dot-and-cross diagram for A l C l 3 and state the C l A l C l bond angle.
Dot-and-cross diagram of A l C l 3 [1] Bond angle: ………………………………. [1] (ii) Unlike A l C l 3 which dimerises to form A l 2 C l 6 , BeC l 2 polymerises and exists as long chains in the solid state. Draw a section of one chain with three BeC l 2 monomers, showing clearly the bonding within the chain. [1] (iii) With a small amount of water, BeC l 2 hydrolyses in the same manner as A l C l 3 . Write an equation for the hydrolysis of BeC l 2 . DHS/2020/II/3d 8 (d) The bond angle in CO 2 is 180 º. The bond angle in SO 2 is approximately 120 º. Explain the difference in the two bond angles given above. [1] EJC/2020/II/1a-c 9 (a) Nitrogen can form a few hydrides such as NH 3 and N 2 H 4 . The boiling points of these two hydrides are given in Table 1.1. Table 1.1 compound boiling point / ºC NH 3 33 N 2 H 4 114 Provide two explanations for why N 2 H 4 has a higher boiling point than NH 3. [2]
(b) When NH 3 is reacted with BF 3 in the gaseous phase, a white solid of NH 3 BF 3 is formed. (i) Draw a dot-and-cross diagram to show the bonding within NH 3 BF 3 and state the shape about the nitrogen atom. [2] (ii) State the type of reaction that NH 3 has undergone with BF 3 , and explain why it is possible. [2] (c) Both NH 3 and PH 3 have trigonal pyramidal shape, but the bond angles in NH 3 are 107º while those in PH 3 are 94º. By considering the electronegativities of the central atoms, suggest why this is so. [2] HCI/2020/II/5b 10 (b) Sidewalks in many cities are paved with Noxer blocks, which are cement mortar coated with TiO 2 to a thickness of 5 to 7 mm. The photocatalytic properties of TiO 2 enables it to remove pollutants from the air, particularly nitrogen dioxide, NO 2 , and nitrogen monoxide, NO, both of which are radicals. (i) Draw a dot-and-cross diagram to show the bonding in NO 2 . [1] (ii) The bond angle in NO2 is experimentally observed to be 135 o . Apply the principles of the VSEPR theory to account for this observation. [2] NYJC/2020/II/1c 11 (c) Lead(II) ethanoate, Pb(CH 3 COO) 2 , also known as sugar of lead is a white crystalline solid which is soluble in water and has a sweet taste. Ancient Romans used sweeteners that contained lead(II) ethanoate to sweeten wine or preserve fruit. Lead(II) ethanoate is no longer used in the production of sweeteners because of its recognised toxicity. Draw simple diagrams to show how a water molecule can be attached to a lead(II) cation, and to an ethanoate anion. Label each diagram to show the type of interaction involved. [3]
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