Question

Vinegar is present in acetic acid. Curd contains ……….acid.
A.Lactic acid
B.Tartaric acid
C.Citric acid
D.None of these

Answer 1

Hint: Acids are the substances which are sour in taste and give hydrogen ions in the solution.
The acids turn blue litmus paper red and have no effect on red litmus paper. The acid present in curd is converted from lactose sugar by the Lactobacillus bacterium.

Complete step-by-step answer:
Acetic acid is available in the vinegar. The curd contains lactic acid. The curd is prepared by the activity of the Lactobacillus bacterium. The organism converts the lactose sugar to lactic acid. This lowers the pH of the milk and the milk gets transformed to the curd. There is the coagulation of the proteins due to acidic pH. Lactic acid enhances the acidic level.
Hence, the correct option is A.

Additional Information:
-An acid reacts with a base to form salt & water.
-They produce ${ H }^{ + }$ ions on dissociation in an aqueous medium.
-Acids are proton donors
-Acids have pH in the range of 1-6 .
-Acids are strong electrolytes.
-Lactic acid is produced due to the anaerobic respiration. During heavy exercise, an ample amount of oxygen is required. When the body is unable to fulfill the oxygen requirement, the body derives the energy through anaerobic respiration in which pyruvic acid is converted into lactic acid.
-Lactic acid fermentation is a type of anaerobic respiration in which pyruvic acid is converted into lactic acid with the production of ATPs.It occurs in bacteria and muscle cells of animals.

Note: The possibility to make a mistake is that you may choose option C. As citric acid is present in lemons, oranges i.e, in sour fruits and curd is also sour but in it, lactic acid is present not citric acid.