3 marksShort AnswerSection A

The pH of a salt used to make tasty and crispy pakoras is 14. Identify the salt and write a chemical equation for its formation. List its two uses.

Q: The pH of a salt used to make tasty and crispy pakoras is 14. Identify the salt and write a chemical equation for its formation. List its two uses.

The salt used to make tasty and crispy pakoras is **baking soda**, which is chemically known as **sodium hydrogencarbonate** ($NaHCO_3$). *(Note: While the question mentions a pH of 14, baking soda is actually a mild, non-corrosive basic salt with a pH of around 8 to 9. A pH of 14 represents a highly corrosive strong alkali like sodium hydroxide).* **Chemical Equation for its Formation:** Sodium hydrogencarbonate is produced using sodium chloride ($NaCl$) as one of the raw materials (Solvay process): $$NaCl + H_2O + CO_2 + NH_3 \rightarrow NH_4Cl + NaHCO_3$$ **Two Uses of Sodium Hydrogencarbonate ($NaHCO_3$):** 1. **As an Antacid:** Being alkaline, it neutralizes excess acid in the stomach and provides relief from acidity. 2. **In Baking:** It is used as an ingredient in baking powder, which decomposes on heating to release carbon dioxide ($CO_2$) gas, making cakes, bread, and pakoras light, spongy, and crispy.

Acids, Bases and Salts

Sodium Hydrogencarbonate (Baking Soda)

Official Answer

The salt used to make tasty and crispy pakoras is baking soda, which is chemically known as sodium hydrogencarbonate ( $NaHCO_3$ ).

(Note: While the question mentions a pH of 14, baking soda is actually a mild, non-corrosive basic salt with a pH of around 8 to 9. A pH of 14 represents a highly corrosive strong alkali like sodium hydroxide).

Chemical Equation for its Formation:

Sodium hydrogencarbonate is produced using sodium chloride ( $NaCl$ ) as one of the raw materials (Solvay process):

$NaCl + H_2O + CO_2 + NH_3 \rightarrow NH_4Cl + NaHCO_3$

Two Uses of Sodium Hydrogencarbonate ( $NaHCO_3$ ):

As an Antacid: Being alkaline, it neutralizes excess acid in the stomach and provides relief from acidity.
In Baking: It is used as an ingredient in baking powder, which decomposes on heating to release carbon dioxide ( $CO_2$ ) gas, making cakes, bread, and pakoras light, spongy, and crispy.

sodium hydrogencarbonateNaHCO3baking sodaNaCl + H2O + CO2 + NH3antacidbaking powder

Marking Scheme

11 mark
21 mark
31 mark

Hint

The salt used in kitchens for crispy pakoras is baking soda ( $NaHCO_3$ ). It is prepared using brine, ammonia, and carbon dioxide.

Quick Oral Answer

The salt is sodium hydrogencarbonate ( $NaHCO_3$ ), commonly called baking soda. It is prepared by reacting sodium chloride, water, carbon dioxide, and ammonia. It is used as an antacid and in baking.

Analysis & Explanation

Identification: Baking soda ( $NaHCO_3$ ) is widely used in Indian kitchens to make crispy pakoras. It is a mild basic salt. The mention of pH 14 in the question is a common technical error in some exam papers, as pH 14 corresponds to a highly corrosive strong base like $NaOH$ , whereas baking soda is safe to consume and has a much lower basic pH (around 8-9).
Preparation: It is manufactured by reacting cold and concentrated sodium chloride solution (brine) with ammonia ( $NH_3$ ) and carbon dioxide ( $CO_2$ ).
Action of Heat: When heated during cooking, it decomposes to release carbon dioxide gas which causes the batter to rise and become airy:

$2NaHCO_3 \xrightarrow{\text{Heat}} Na_2CO_3 + H_2O + CO_2$

Common Mistakes

1Confusing baking soda ( $NaHCO_3$ ) with washing soda ( $Na_2CO_3$ ).
2Writing the formula of sodium hydrogencarbonate incorrectly.
3Accepting pH 14 literally without noting that baking soda is a mild base (eating a substance with pH 14 would cause severe chemical burns).

Interesting Facts

Baking soda is also used in soda-acid fire extinguishers because it releases carbon dioxide gas when it reacts with acid, which helps smother fires.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2018?

This question carries 3 marks in the CBSE Class 10 Science 2018 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Acids, Bases and Salts" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Sodium Hydrogencarbonate (Baking Soda)" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2018 paper?

This is a Short Answer question from Section A in the CBSE Class 10 Science 2018 paper.