Science (086) — AI-generated practice question

Baking soda (NaHCO₃) decomposes on heating to release CO₂ gas:

$$2\text{NaHCO}_3 \xrightarrow{\Delta} \text{Na}_2\text{CO}_3 + \text{H}_2\text{O} + \text{CO}_2\uparrow$$

This CO₂ makes the cake rise, giving it a light, fluffy texture.

Washing soda (Na₂CO₃·10H₂O) is sodium carbonate, a strongly alkaline salt. It does not decompose on baking to release CO₂. Without CO₂ gas being produced, no air bubbles are formed in the batter, so the cake does not rise and remains flat and dense.

Source: Chapter 2, Uses of Salts / Baking Soda and Washing Soda

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• Examiners want you to name both compounds correctly (NaHCO₃ and Na₂CO₃), state the decomposition equation for baking soda, and clearly link CO₂ production to the cake rising.
• The key contrast: baking soda → releases CO₂ on heating; washing soda → no such decomposition, so no leavening action.
• Writing the chemical equation earns a dedicated mark; don't skip it.