Question

12.
If 10 mL of H2SO4 is mixed with 10 mL of Mg(OH)2 of the same
concentration, the resultant solution will give the following colour with
universal indicator :
(A) Red
(B) Yellow
(C) Green
(D) Blue
​

Answer 1

Blue Colour is Obtained

Explanation:

• Magnesium Hydroxide, when treated with Sulphuric Acid, forms a reaction, named Neutralization Reaction.  

• Salt along with Water comes as a by-product when there is reaction between Base & Acid. (Neutralization Reaction)  

In this reaction, magnesium hydroxide, which is a base, reacts with sulfuric acid to form magnesium sulphate, which is a salt, and two molecules of $H_2O$.

• The reaction can be represented in the form of an equation:-

$Mg(OH)_2 + H_2SO_4$ → $MgSO_4 + 2H_2O$

Answer 2

The resultant solution will give (C) green with universal indicator.

Explanation:

• Magnesium sulfate react with sulfuric acid to produce magnesium hydrosulfate which is a neutral salt.
• Mg(OH)₂ + H₂SO₄ → 2Mg(HSO₄)
• The universal indicator is used to identify the strength of the pH of a solution.
• The color of the indicator changes with respect to the acidic and basic value of the solution.
• When the pH is strong acidic then the color becomes red; when the pH is weak acidic then the color becomes orange; the pH is neutral salt then the color becomes green; the pH is weak alkali then the color becomes blue; and the pH is strong alkali then the color becomes purple.
• Thus, the color of the universal indicator changed into green in this reaction.