Compounds of the alkali metals
3 marks · EasyA student observes three alkali metals exposed to air. The table shows her results.
| Metal | Time for surface to become dull / min |
|---|---|
| Lithium | 8 |
| Sodium | 4 |
| Potassium | 1 |
Which metal reacts fastest with air?
Which metal reacts slowest with air?
State the trend in reactivity of these metals with air.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Potassium · must show Potassium is fastest
(b) Lithium · must show Lithium is slowest
(c) Reactivity increases going down the group (potassium is most reactive, lithium is least). · must show States correct trend
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Marking points
B1 (a) · 1 mark · Identifies potassium as the most reactive/fastest.
B1 (b) · 1 mark · Identifies lithium as the least reactive/slowest.
B1 (c) · 1 mark · States that reactivity increases down the group.
Worked solution
a) Potassium is the fastest to react with air, as its surface becomes dull in only 1 minute. b) Lithium is the slowest, as it takes 8 minutes to become dull. c) The trend is: reactivity increases going down the group.