Question

Baking powder contains sodium hydrogen carbonate, and
A. Tartaric acid
B. Sodium carbonate
C. Calcium chloride
D. Acetic acid.

Answer 1

Hint: The backing soda has a weak acid in its composition. The weak acid is utilized to neutralize the basic salts.

Step by step answer: Baking soda is a mixture of bases such as carbonate or bicarbonate, weak acid, and buffer.
The chemical formula of baking powder is ${\text{NaHC}}{{\text{O}}_{\text{3}}}$.
When the baking powder is heated with the food, sodium hydrogen carbonate releases gas in the form of bubbles. This gas increases the volume of the dough. So, the baking powder is used to give the volume to the dough.
The sodium hydrogen carbonate decomposes as follows:
${\text{2NaHC}}{{\text{O}}_{\text{3}}}\,\mathop \to \limits^\Delta {\text{N}}{{\text{a}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}\,{\text{ + }}\,{\text{C}}{{\text{O}}_{\text{2}}}\, + \,{{\text{H}}_2}{\text{O}}$

The decomposition of sodium hydrogen carbonate on heating produces sodium carbonate, carbon dioxide, and water.
To neutralize the sodium carbonate, a weak acid such as tartaric acid is added to the sodium hydrogen carbonate.

So, option (A), is correct.
Sodium carbonate is produced by the decomposition of sodium hydrogen carbonate; it is not added to the baking powder, so option (B) is incorrect.

The calcium chloride and acetic acid do not react as well as the tartaric acid reacts with sodium carbonate so they are not added with the sodium hydrogen carbonate in baking powder. So, option (C) and (D) are incorrect.
If the tartaric acid is not added to the baking powder, the test of food will be bitter due to the presence of sodium carbonate.

Therefore, option (A) tartaric acid is correct.

Note: Both, tartaric acid and acetic acid are weak acids and both give the same reaction with sodium hydrogen carbonate even only the tartaric acid is added in baking powder. The acid added in a baking powder can be slow or fast reacting. The slow-reacting acid only reacts when the baking powder is heated whereas the fast-reacting acid reacts at room temperature that is why some dough gains volume on heating whereas some dough gains volume in sunlight.