O-LevelChemistryMetals & Reactivity5070/22 · Oct/Nov 2019 · Q58 Marks

The table shows some properties of four Group I elements. element | melting point /°C | relative thermal conductivity | atomic radius /nm ---|---|---|--- lithium | 181 | 84 | 0.157 sodium | | 142 | 0.191 potassium | 63 | | 0.235 rubidium | 39 | 58 |

(a)(i)Complete the table by estimating: • the melting point of sodium • the atomic radius of rubidium.[2]
(a)(ii)Use the information in the table to suggest why it is difficult to predict the relative thermal conductivity of potassium.[1]
(b)(i)Sodium reacts with oxygen to produce sodium oxide, Na2O. Construct the equation for this reaction.[1]
(b)(ii)What type of oxide, acidic or basic, is sodium oxide? Give a reason for your answer. type of oxide: reason:[1]
(c)Explain, in terms of ease of formation of ions, why copper does not react with aqueous sodium sulfate.[1]
(d)Hydrated sodium iodate(V) has the formula NaIO3.xH2O. It has a relative formula mass of 288. Calculate the value of x in this formula. X =[2]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.

[1] melting point of sodium: values between 70 °C and 170 °C (inclusive)
[1] atomic radius of rubidium: values between 0.240 nm and 0.320 nm (inclusive)
[1] there is no trend / the values go up and down
[1] 4Na + O2→ 2Na2O
[1] basic oxide AND because sodium is on the left of the Periodic Table / basic oxide AND because sodium is a metal
[1] copper does not form ions as easily as sodium / sodium forms ions more easily than copper
[2] x = 5
[1] if 2 marks not scored 1 mark for: molar mass of NaIO3 = 198

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