Question

A solution of sodium carbonate in water has a pH value:
(A) >7
(B) <7
(C) 7
(D) Equal to zero

Answer 1

We will first write down the reaction. Based on the observation whether the product is acidic or basic we will mention its pH. Sodium carbonate is formed from a weak acid and strong base.

Complete step by step answer
We already know pH is a measure of how acidic/basic water is. The range goes from 0 - 14, with 7 being neutral. pH of less than 7 indicates acidity, whereas a pH of greater than 7 indicates a base. pH is really a measure of the relative amount of free hydrogen and hydroxyl ions in the water.
We will first write down the reaction:
Since, $N{{a}_{2}}C{{O}_{3}}$ is a salt formed from weak acid and salt strong base.
$CO_{3}^{2-}+{{H}_{2}}O\to {{H}_{2}}C{{O}_{3}}+9O{{H}^{-}}$
So, the solution is releasing $O{{H}^{-}}$ ions,
Thus, it is basic in nature. The pH value should be greater than 7.
We need to select the correct option.
The correct option is A.

Note
In chemistry, pH, 'power of hydrogen' is a scale used to specify the acidity or basicity of an aqueous solution. Acidic solutions (solutions with higher concentrations of hydronium ions) are measured to have lower pH values than basic or alkaline solutions. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic. Mostly measured pH values will lie in the range 0 to 14, though negative pH values and values above 14 are entirely possible. Since pH is a logarithmic scale, a difference of one pH unit is equivalent to a tenfold difference in hydrogen ion concentration. If pure water is exposed to air it becomes mildly acidic.