Q19.137CP - Chemistry: Molecular Nature Of Matter And Change

Question

Litmus is an organic dye extracted from lichens. It is red below$\mathbf{\text{pH 4.5}}$ and blue above $\mathbf{\text{pH 8.3}}$. One drop of either$\mathbf{\text{0.1 M HCl ( pH1}}$) or a$\mathbf{\text{pH3}}$ buffer changes blue litmus paper to red, but a drop of $\mathbf{\text{0.001 M HCl}}$(also$\mathbf{\text{pH3}}$) does not. Explain.

Step-by-Step Solution

Answer

The color of litmus remained unchanged.

 

Step 1: Definition of Concept

Capacity: The amount of heat energy required to raise the temperature of a body by a certain amount is known as heat capacity. The amount of heat in joules required to raise the temperature 1 Kelvin is known as heat capacity (symbol: C) in SI units.

Step 2:Explain the given statement

The color of Litmus is red below $\text{pH4.5}$and its color will change to blue with the change of pH. At the above$\text{8.3pH}$ it shows blue color.

When either 1 drop of$\text{0.1MHCl}$ which has $\text{pH1}$or one drop of a solution with$\text{pH3}$ add to the litmus paper, its color changed from blue to red. But when a drop of $\text{0.001MHCl}$  which has $\text{pH3}$add, it color did not change from blue to red. It remains blue.

Because when add 1 drop of $\text{0.1MHCl}$which has$\text{pH1}$ or one drop of a solution with $\text{pH3}$add to the litmus paper its pH come close to 3 and at below $\text{4.5pH}$it has red color. While when a drop of $\text{0.001M HCl}$which has$\text{pH3}$ add to the litmus, the pH of litmus will not come below. $\text{4.5pH}$

Therefore,   the color of litmus remained unchanged.