Question

A water soluble base in solution produces:
A. $O{{H}^{-}}$ ions
B. ${{H}^{+}}$ions
C. ${{H}^{-}}$ ions
D. $O{{H}^{+}}$ions

Answer 1

Hint: Solubility is a property which refers to the ability to dissolve in a solvent for a given substance, the solute. It is calculated at equilibrium in terms of the cumulative volume of solute dissolved in a solvent. The solution which results is called a saturated solution. Acids are those which produce hydrogen ions in water while bases are substances which react and neutralize acids, to produce water as a product.

Complete answer:
- We know that bases are those substances which release hydroxide ions in aqueous solutions.
- And those bases which are soluble in water are known as Alkali.
- We define alkali as a basic, ionic salt of alkali metal.
- Alkaline solutions are the basic solutions of alkali metals that are soluble in water.
- The pH level of bases soluble in water are higher than 7.
- As we know a water soluble base gives hydroxyl ions $O{{H}^{-}}$,these hydroxyl ions are responsible to give the alkalinity to make the pH of the solution greater than 7.
- Bases can be classified as Strong and Weak Bases.
- Strong bases are those which are fully ionic i.e. 100% dissociation into metal and hydroxide ions in solution.
- Sodium hydroxide and potassium hydroxide are some common examples of Strong bases.
     \[NaOH+{{H}_{2}}O\to N{{a}^{+}}\left( aq \right)+O{{H}^{-}}\left( aq \right)\]
- Whereas weak bases which do not completely dissociate into Hydroxide ions.
- An example of a weak base can be ammonia, here note that ammonia does not contain any $O{{H}^{-}}$ions but is still considered a weak base.
- It is because as discussed above bases are those which can produce $O{{H}^{-}}$ions, so when ammonia is reacted with water it also produces $O{{H}^{-}}$ions.
     \[N{{H}_{3}}\left( aq \right)+{{H}_{2}}ON{{H}_{4}}^{+}\left( aq \right)+O{{H}^{-}}\left( aq \right)\]
As we can see the reaction is a reversible reaction and only 1% produces hydroxide ions, the remaining 99% remain as ammonia molecules. This is why it is considered as a weak base.
- We can determine if a base is a strong or weak base through its ${{K}_{b}}$or $p{{K}_{b}}$values.
     \[{{K}_{b}}=\frac{\left[ \ddot{B}{{H}^{+}} \right]\left[ O{{H}^{-}} \right]}{\left[ {\ddot{B}} \right]}\]
- The relationship between ${{K}_{b}}$and $p{{K}_{b}}$is:
     \[p{{K}_{b}}=-{{\log }_{10}}{{K}_{b}}\]
- Strength of base ∝ ${{K}_{b}}$i.e. more is the ${{K}_{b}}$value stronger is the acid or vice versa.
- While strength of base ∝ $\frac{1}{p{{K}_{b}}}$i.e. more is $p{{K}_{b}}$value weaker is the acid or less is the $p{{K}_{b}}$value stronger is the acid.

Hence a water soluble base in solution produces is option A. $O{{H}^{-}}$ ions.

Note: ${{K}_{b}}$ is the equilibrium constant of the reaction
     \[\ddot{B}\left( aq \right)+{{H}_{2}}O\left( l \right)\rightleftharpoons \ddot{B}{{H}^{+}}\left( aq \right)+O{{H}^{-}}\left( aq \right)\]
Weaker the base, the further the to left is the equilibrium position. Lower is the value of constant, the more the equilibrium lies to the left.