Question

The solution of $ N{a_2}C{O_3} $ has $ pH $
(A) Greater than 7
(B) Less than 7
(C) Equal to 7
(D) Equal to zero.

Answer 1

Hint: $ pH $ is defined as the negative logarithm to the base 10 of concentration of hydrogen ions in the solution. $ pH $ is calculated to know about the nature of the solution whether it is acidic, basic or neutral.

Complete step by step answer:
Value $ pH $ varies from 0 to 14. Lesser the value of $ pH $ , more the solution will be acidic. At $ pH $ =7 the solution is neutral and as we move towards the larger value, the solution will be more basic.
Here, we need to find $ pH $ of $ N{a_2}C{O_3} $ that is commonly known as Sodium carbonate. When this salt is dissolved in water, it undergoes hydrolysis as follows:
 $ N{a_2}C{O_3} + {H_2}O \to 2NaOH + {H_2}C{O_3} $
As we can see, on reacting with water the products formed are Sodium Hydroxide and Carbonic Acid. Sodium hydroxide is a base of an alkali metal that is sodium and is known for its strong basic nature. On the other hand, Carbonic Acid is one of the weak acids composed of a carbonate ion and two hydrogen ions.
The solution has a weak acid and strong base as its final products. Thus the basic nature will be dominating over the acidic one. The resultant solution will be the basic one and as discussed earlier, the basic solutions have pH greater than 7. This means that concentration of hydroxide ions will be greater than hydrogen ions inside the solution.
So our correct answer is the option A. greater than 7.

Note:
When $ pH $ is equal to 7, the solution is neutral. When $ pH $ is less than 7, the solution is acidic. When $ pH $ is greater than 7, the solution is basic. As the value of approaches zero (minimum), the solution becomes highly acidic. As the value of approaches 14(maximum), the solution becomes highly basic.