Test: Introduction to Acids & Bases - UPSC MCQ

The acid present in curd is lactic acid. Curd forms due to the chemical reaction between lactic acid bacteria and milk protein casein. The increased acidity causes the milk proteins (casein) to tangle into solid masses or curds.

Blue litmus paper turns red under acidic conditions. It will turn red when it comes into contact with an acid. If it comes into contact with a substance that is basic or neutral, it will remain blue.

Acids like acetic acid (CH₃COOH) dissociate partially or incompletely, releasing only some of their hydrogen atoms into the solution. Hence it is a weak acid.

Option A: Lactic acid is found in curd
Option B: Citric acid is found in Oranges
Option C: Oxalic acid is found in tomatoes
Option D: Acetic acid is found in vinegar

Thus, option D is correct.

Limewater is the common name for a dilute aqueous solution of calcium hydroxide.
Calcium hydroxide, Ca(OH)₂, is sparsely soluble at room temperature in water (1.5 g/L at 25 °C). It is basic in nature with a pH of 12.4.

KOH (aq), or Potassium Hydroxide, is a strong base. When added to water, it dissociates completely to give mobile ions, including the hydroxide ion which is responsible for the alkaline properties of the substance.

Gypsum: CaSO4₄.2H​₂O
Plaster of paris: CaSO₄​.0.5H₂​O.

The difference in number of water molecules is = 2 - 0.5 = 1.5 = 3/2

Sulfuric acid is inorganic because it doesn't contain carbon atoms bonded to oxygen, nitrogen and hydrogen atoms. 

Option A: Lemon juice in its natural state is acidic with a pH of about 2, but once metabolized it actually becomes alkaline with a pH well above 7. So, outside the body, anyone can see that lemon juice is very acidic.

Option B: Tomatoes are on the low end of acidic foods. An alkaline diet is not that you can not have any foods that are acidic but a balance of both alkaline and acidic.

Option C: Milk is actually pretty close to neutral with a pH of 6.8 (slightly acidic). It can become acidic if bacteria break down the milk sugar and produce lactic acid. This is what causes milk to sour.

Thus, option D is correct.

The acid that is present in tamarind is tartaric acid, which is a white crystalline organic acid.

If we add water to acid, the reaction would become highly exothermic and lots of heat would be generated which would splash​ on your face and cause severe burns.

Thus, Option C is correct.

Acids dissociate in water to give H⁺ ions and not OH^-. OH- ions are released on dissociation of bases in water.

Most acids release H⁺ ions in water, which combines with water molecules to produce hydronium (H₃O⁺) ions.
Example: HCl(g) + H₂O(l) → Cl⁻(aq) + H₃O⁺(aq)

A base is bitter in taste and soapy to touch. A weak base does not dissociate completely into its ions in aqueous solutions.

Acid is defined as the substance which dissociates and releases H⁺ ions in their aqueous states.
HCl (aq.) gives H⁺ (aq.) in aqueous solution.
But molecules like alcohol, glucose, and Urea do not produce H⁺ ions and thus are not considered acids.

CuSO₄.5H₂O is a hydrated salt. An example of acid salt is NaHCO₃.

HCL is an acid so it won't have any effect on red litmus paper

Calcium Hydroxide (not carbonate) is commonly referred to as slaked lime.

An element which is common to all acids is Hydrogen because acids dissociate into H⁺ ions.

An oxy acid is an acid that contains an oxygen atom bonded to a hydrogen atom and at least one other element.
General structure: X-O-H