You are to determine the concentration of a solution of tetraoxosulphate (VI) acid by titrating it with sodium trioxocarbonate (IV) as the standard solution. Name a suitable indicator for the titration.

a)
i. A suitable indicator for the titration of a strong acid ($\text{H}_2\text{SO}_4$) with a weak base ($\text{Na}_2\text{CO}_3$) is one that changes color in the acidic pH range.

$$\boxed{\text{Methyl orange}}$$

ii. State the colour of your chosen indicator:
I. In the base:

$$\boxed{\text{Yellow}}$$

II. At the end point during titration:

$$\boxed{\text{Orange}}$$

iii. Why was the indicator used?
The indicator was used to visually determine the end point of the titration. Methyl orange is suitable because its color change range (pH 3.1-4.4) matches the acidic pH at which the equivalence point of a strong acid-weak base titration occurs.