Question

How do you make a saturated solution of sodium bicarbonate?

Answer 1

Hint The solubility of a substance depends on the temperature. The saturated substances are those that cannot dissolve further addition of the solute.

Complete step by step solution:
So in the question, it is asked how we will make the saturated solution of sodium bicarbonate. Before going into the solution part of the question, we should first discuss the solution, solute, solvent and saturated solution.
From the lower classes we are studying about various solutions. The solutions are those homogenous mixtures which are made up of two or more substances. Generally we refer to the solutions in the liquid phase but the solute and solvents are also present in other phases.
The solute are those substances which get dissolved in the dissolving medium to form the solution, we generally refer to those substances in solid phase as the solute.
Solvent is the medium in which the solute is getting dissolved to form the solution.
Now let’s discuss the saturated solution. We generally say the saturated solution as the solutions which cannot dissolve further solutes in them, but actually the saturated solution is a system which is in equilibrium state i.e. When a solution is said to be saturated when the solute is dissolved in solution and the solute that precipitates out from the solution is happening at the same rate.
Here we are concerned about making a saturated solution. Actually we cannot say the exact weight or amount of sodium carbonate which is required for making the saturated solution since the saturation varies when the volume of the solvent changes .
But we could say approximately that, an amount of about 6-8g of $\text{NaHC}{{\text{O}}_{\text{3}}}$ crystals are dissolved in 100ml of water to make the saturated solution.
Now let’s take the dissolution reaction of $\text{NaHC}{{\text{O}}_{\text{3}}}$
$\text{NaHC}{{\text{O}}_{\text{3}}}_{\left( s \right)}\rightleftharpoons \text{NaHC}{{\text{O}}_{\text{3}}}_{\left( aq \right)}$
Now let’s discuss the solubility of $\text{NaHC}{{\text{O}}_{\text{3}}}$ and let's write the dissociation constant as ,${{\text{K}}_{\text{sp}}}\text{=}\dfrac{\text{NaHC}{{\text{O}}_{\text{3}}}_{\left( \text{aq} \right)}}{\text{NaHC}{{\text{O}}_{\text{3}}}_{\left( \text{s} \right)}}\text{=NaHC}{{\text{O}}_{{{\text{3}}_{\left( \text{aq} \right)}}}}$
Since for solid components we will cannot concentrate.
The $\text{NaHC}{{\text{O}}_{{{\text{3}}_{\left( \text{aq} \right)}}}}$exists in the solution as, $\text{N}{{\text{a}}^{\text{+}}}$ and$HCO_{3}^{-}$
So let’s write the equation as, ${{\text{K}}_{\text{sp}}}\text{=NaHC}{{\text{O}}_{{{\text{3}}_{\left( \text{aq} \right)}}}}=\left[ N{{a}^{+}} \right]\left[ HCO_{3}^{-} \right]$
The solubility of saturated solution of sodium bicarbonate increases as the temperature increases since on heating the kinetic energy of the atoms increases and undergoes effective collisions and ddissolve effectively.

Note: When a salt containing sodium ion is added to the solution then the backward reaction occurs and the sodium bicarbonate is precipitated, this happens because of the common ion effect. The saturation can be removed by diluting the solution by adding more amount of solvent and we could concentrate the solution by distillation process i.e. by simple heating in which the water molecule is escaped as water vapor.