O-LevelChemistryMetals & Reactivity5070/22 · Oct/Nov 2014 · Q212 Marks

The table shows some properties of the Group I metals. metal | density in g/cm³ | melting point /°C | boiling point /°C ---|---|---|--- lithium | 0.53 | 181 | 1342 sodium | 0.97 | 98 | 883 potassium | 0.86 | 63 | rubidium | 1.53 | 39 | 686 caesium | 1.88 | 29 | 669

(a)(i)Describe the general trend in the density of the Group I metals.[1]
(a)(ii)Predict the boiling point of potassium.[1]
(a)(iii)What is the physical state of caesium at 35°C? Explain your answer.[1]
(b)(i)Describe the trend in reactivity of the Group I metals with water.[1]
(b)(ii)Construct the equation for the reaction of rubidium with water.[1]
(b)(iii)The reaction of rubidium with water is exothermic. What is meant by the term exothermic?[1]
(c)Sodium and calcium form ionic hydrides containing the hydride ion, H¯. Sodium and calcium hydrides react with water to form the hydroxide and hydrogen. NaH + H₂O → NaOH + H2 CaH2 + 2H₂O → Ca(OH)2 + 2H2 Deduce the general ionic equation for these reactions.[1]
(d)(i)Sodium is a soft metal with little catalytic activity. Nickel is a hard metal which is often used as a catalyst. Describe two other differences in the physical properties of sodium and nickel.[2]
(d)(ii)State one industrial use of nickel as a catalyst.[1]
(d)(iii)Explain why an alloy of nickel and copper is less malleable than copper alone.[2]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2014). The mark or mark type is shown in brackets.

[1] A2 (a) (i) (density generally) increases down the group (1)
[1] A2 (a) (ii) allow between 710 – 860 (°C) (1) (actual value = 760°C)
[1] A2 (a) (iii) liquid (no mark on its own) melting point is below 35 (°C) AND boiling point is above 35(°C) (1)
[1] A2 (b) (i) more reactive down the group/less reactive up the group (1)
[1] A2 (b) (ii) 2Rb + 2H2O → 2RbOH + H2 (1)
[1] A2 (b) (iii) reaction which releases heat/releases energy/products have lower energy than reactants/reaction in which ∆H is negative/temperature (of surroundings) increases (1)
[1] A2 (c) H¯ + H2O → OH⁻ + H2 (1)
[1] A2 (d) (i) sodium has low density/nickel has high density (1)
[1] A2 (d) (i) sodium has low melting point / nickel has high melting point/sodium has low boiling point/nickel has high boiling point (1)
[1] A2 (d) (ii) any suitable use e.g. manufacture of margarine/other stated hydrogenation reactions e.g. cyclohexane from benzene/sorbitol from glucose/amines from nitro-compounds/amines from nitriles/alkanes from alkenes/alkanes from alkynes (1)
[1] A2 (d) (iii) nickel ions are different size to copper ions (1)
[1] A2 (d) (iii) idea of disruption of layers in metallic structure/layers cannot slide as easily (1) NOTE: there MUST be some idea of layers/rows or sheets sliding not just atoms sliding

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