From the list given below, select the word(s) required to correctly complete blanks (i) to (ii) in the following passage. The words from the list are to be used only once. Write the answers as (a) (i), (ii), (iii). Do not copy the passage.
[ammonia, ammonium, carbonate, carbon dioxide, hydrogen, hydronium, hydroxide, precipitate, salt, water):
(i) A solution M turns blue litmus red, so it must contain (i) ....................... ions, another solution O turns red litmus blue and hence, must contain (ii) ..................... ions.
(ii) When solutions M and O are mixed together, the products will be (iii) .......... and (iv) ·····················
(iii) If a piece of magnesium was put into a solution M, (v) ..................... gas would be evolved.

Explanation

(v) Hydrogen