A-LevelChemistryChemical periodicity9701/23 · May/June 2021 · Q311 Marks

Separate samples of R, S, T and U are added to cold water. The identity of each sample is unknown. However, each sample is known to be pure and can only be one of Ba(OH)2, NaCl, P4O10 or SiCl4. [Table with state at room temperature, observations on addition of sample to water]

(a)(i)Use the observations in the table to identify each sample as one of Ba(OH)2, NaCl, P4O10 and SiCl4. Write your answers in the table. [Table with R, S, T, U][4]
(a)(ii)Identify the formula of the white solid made when sample T reacts with water.[1]
(a)(iii)Name the solution formed when sample U reacts with water.[1]
(b)(i)Magnesium oxide and aluminium oxide have properties typical of ceramic materials. Name one physical property typical of ceramic materials.[1]
(b)(ii)Give the formula of another Period 3 oxide which behaves as a ceramic material.[1]
(c)Tungsten oxide, WxOy, is used to give colour to ceramic materials. A sample of WxOy contains 79.29% tungsten by mass. Calculate the empirical formula of WxOy. Show your working. empirical formula =[3]

Mark scheme

Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.

[4] 3(a)(i) M1 Ba(OH)2 OR barium hydroxide
[1] M2 NaCl OR sodium chloride
[1] M3 SiCl4 OR silicon(IV) chloride
[1] M4 P4O10 OR phosphorus(V) oxide
[1] 3(a)(ii) SiO2
[1] 3(a)(iii) phosphoric acid / phosphoric(V)acid
[1] 3(b)(i) any one physical property typical of ceramic materials from: • strong / retain strength (over certain temperatures / conditions) • non-conductors of electricity / electrical insulators • high melting points
[1] 3(b)(ii) SiO2
[1] 3(c) M1 % of O 100 - 79.29 (= 20.71)
[1] M2 express W and O as mol by /183.8 and /16 respectively
[1] M3 divide each by smallest number to give empirical formula WO3

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