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Buffers Quiz 2

chemistry

Among the following choose the correct option on which the pH range of the acidic  buffer solution depends:

 According to Henderson's equation pH of acidic buffer solution depends on the negative log of the acid dissociation constant and the ratio of salt to acid concentrations.

As we know from the ionic equilibrium that the formula of Henderson's equation for acidic buffer solution is given as $ \\ pH=p{{K}_{a}}+\log \dfrac{\text{[conjugate base]}}{[Acid]} \\ $ OR $ \\ \dfrac{[Salt]}{[Acid]} \\ $ Therefore the pH of acidic buffer solution depends on the negative log of acid dissociation constant $(p{{K}_{a}})$ and the ratio of conjugate base or salt and acid concentration.

 Which of the following will act as a basic buffer solution when equimolar amounts of both the compounds are present in the solution?

 Basic buffer solutions are those solutions in which the weak base and the conjugate acid or salt of that base present.

As we know, a basic buffer is an aqueous solution of a mixture of weak base and conjugate acid or salt of the same weak base with any strong acid. So, from the first option we can see that $N{{H}_{3}}$  is a weak base and $NH_{4}^{+}$  is the conjugate acid. In the second option  $N{{H}_{4}}OH$ and $N{{H}_{4}}Cl$ is the salt of same weak base with strong acid (HCl)  and in option three $N{{H}_{4}}OH$ is the weak base but $C{{H}_{3}}COON{{H}_{4}}$ is the salt  of weak acid. Therefore both option A and B are correct. 

 Choose the correct representation of the Henderson's equation for the pH value of acidic buffer solution:

 In this equation pH of acidic buffer solution depends on the negative log of the acid dissociation constant and the ratio of salt to acid concentrations.

 As we know from the ionic equilibrium that the formula of Henderson's equation for acidic buffer solution is given as $ \\ pH=p{{K}_{a}}+\log \dfrac{[conjugate\text{ }base]}{[Acid]} \\ $ OR $ \\ \dfrac{[Salt]}{[Acid]} \\ $  Therefore the pH of acidic buffer solution depends on the negative log of acid dissociation constant $(p{{K}_{a}})$ and the ratio of conjugate base or salt and acid concentration.

 What will be the maximum buffer action condition of the acidic and basic buffer solutions?

 In the maximum buffer action condition of acidic and basic buffer solution the concentration of acid and its salt and the concentration of base and its salt become 1:1.

 In the maximum buffer action condition of acidic buffer solution the concentration of weak acid and its salt become $1:1$ $\\ \underset{1}{\mathop{\left[ C{{H}_{3}}COOH \right]}}\,:\underset{1}{\mathop{\left[ C{{H}_{3}}COONa \right]}}\,\\ \therefore pH=p{{K}_{a}}+\log \dfrac{1}{1}\\ \text{Thus, }pH=p{{K}_{a}} \\ $ In the maximum buffer action condition of basic buffer solution the concentration of weak base and its salt become $1:1$ $ \\ \underset{1}{\mathop{\left[ N{{H}_{4}}OH \right]}}\,:\underset{1}{\mathop{\left[ N{{H}_{4}}Cl \right]}}\,\\ \therefore pOH=p{{K}_{b}}+\log \dfrac{1}{1}\\ \text{Thus, }pOH=p{{K}_{b}}$.

 What is the formula of buffer capacity, what measurement does it show for the buffer and what will happen when the value of buffer capacity will be large?

  Buffer capacity is the ratio of the number of moles of acid or may be based on one liter of the solution to change the negative log of ${{H}^{+}}$ by one unit.

 Buffer capacity is defined as the number of moles of base or acid which is added in one liter of buffer solution to change the pH by one unit and it is given as   $ \\ $ Buffer capacity = $\dfrac{\text{No}\text{. of moles of acid or base per liter}}{\text{Change in pH of buffer solution}}$ $ \\ $ Buffer capacity measures the effectiveness and not the concentration of buffer and the value of buffer capacity will be large when there will be more resistance in the solution to pH change.