Generated by claude-sonnet-4-6 · 2026-06-15 06:46 · grounding rag
Model Answer
(i) Compound X is Plaster of Paris.
Chemical formula: $\text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O}$
(ii) Baking soda contains only sodium hydrogen carbonate ($\text{NaHCO}_3$), whereas baking powder contains sodium hydrogen carbonate along with a mild edible acid (such as tartaric acid).
Explanation
- For (i), Plaster of Paris is made from gypsum ($\text{CaSO}_4 \cdot 2\text{H}_2\text{O}$) by heating; its formula with the ½ water of crystallisation must be written correctly.
- For (ii), the key distinction is that baking powder = baking soda + mild acid (+ starch). Examiners expect you to name the extra component; just saying "it has more ingredients" is insufficient.