Compounds of the alkali metals
3 marks · EasySodium chloride, potassium bromide, and lithium iodide are all compounds of Group 1 metals.
State the usual colour of sodium chloride.
Which one of these compounds is most likely to be soluble in water?
Explain why most Group 1 metal compounds form colourless solutions.
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(a) White · must show Correctly states white
(b) All are soluble, but sodium chloride is highly soluble in water. · must show Correct choice: sodium chloride
(c) Because Group 1 metal ions are colourless, so their solutions are colourless unless the negative ion is coloured. · must show States metal ions are colourless
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Marking points
B1 (a) · 1 mark · States the usual colour of sodium chloride is white.
B1 (b) · 1 mark · Correctly names a Group 1 compound as soluble (any of the three is correct, but sodium chloride preferred).
B1 (c) · 1 mark · Gives a correct reason: Group 1 ions are colourless.
Worked solution
a) The usual colour of sodium chloride is white. b) All three compounds are soluble in water, but sodium chloride is a common example of a highly soluble Group 1 compound. c) Most Group 1 compounds form colourless solutions because Group 1 metal ions are colourless, so unless the negative ion is coloured, the solution remains colourless.