Science — AI-generated practice question

(a) Preparation of Sodium Hydrogencarbonate (Baking Soda):

Baking soda is prepared from sodium chloride (common salt) by passing carbon dioxide and ammonia gas through a concentrated solution of sodium chloride (brine). The chemical equation is:

$$\text{NaCl} + \text{H}_2\text{O} + \text{CO}_2 + \text{NH}_3 \rightarrow \text{NH}_4\text{Cl} + \text{NaHCO}_3$$

Ammonium chloride remains dissolved while sodium hydrogencarbonate, being less soluble, precipitates out and is collected.

(b) Three Uses of Baking Soda:

1. Used in making baking powder (mixture with tartaric acid); releases CO₂ to make cakes/bread soft and spongy.
2. Used as an antacid to neutralise excess acid in the stomach.
3. Used in soda-acid fire extinguishers.

(c) Baking Soda as Antacid:

The stomach produces hydrochloric acid during digestion. When excess acid is secreted, it causes indigestion/acidity. Baking soda (NaHCO₃) is a mild, non-corrosive basic salt. Being alkaline, it neutralises the excess acid in the stomach, providing relief from acidity.

Source: Chapter 2, Section 2.4.3

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• Part (a) is typically 2 marks — include the equation and one line on the process.
• Part (b) is 2 marks — list exactly three uses; the textbook gives three, so write all three.
• Part (c) is 1 mark — key phrase is "alkaline/basic nature neutralises excess acid". Keep it to 2–3 lines.
• Do not confuse "antacid" (neutralises acid) with "acid" — baking soda is basic, not acidic.
• The equation in part (a) must be written exactly as given in the textbook.