Answer: 1. B. 1.3
2. D. self-ionization
3. A. acidic
4. HCl is a weak acid; [tex]CH_3COOH[/tex] is a weak acid.
5. A. [tex]K_b=\frac{[OH^-][C_5H_5NH^+]}{[C_5H_5N]}[/tex]
Explanation:
1. pH is the negative logarithm of hydrogen ion concentration.
[tex]pH=-log[H^+][/tex]
Given: [tex][H^+]=5.0\times 10^{-2}=0.05[/tex]
[tex]pH=-log[0.05M]=1.30[/tex]
2. An acid is a substance which donates [tex]H^+[/tex] ions when dissolved in water.
A base is a substance which donates [tex]OH^-[/tex] ions when dissolved in water.
Thus as water ionizes to give both ions, it acts as both acid and base.
[tex]H_2O\rightarrow H^++OH^-[/tex] which is called as self ionization.
3. pH is the measure of acidity or alkalinity of a solution. \Acids have pH less than 7, neutral solutions have pH of 7 and basic solutions have pH more than 7.
As the given solution has a pH of 6.8 which is less than 7, it is an acidic solution.
4. Strong acids are those acids which undergo complete dissociation when dissolved in water.
[tex]HCl\rightarrow H^++Cl^-[/tex]
Weak acids are those acids which do not undergo complete dissociation when dissolved in water.
[tex]CH_3COOH\rightleftharpoons CH_3COO^-+H^+[/tex]
5. Dissociation constant is the ratio of product of concentration of products to the product of concentration of reactants each raised to their stochiometric coefficients.
[tex]C_5H_5N+H_2O\rightarrow C_5H_5NH^++OH^-[/tex]
[tex]K_b=\frac{[OH^-][C_5H_5NH^+]}{[C_5H_5N]}[/tex]
The concentration of water is ignored as it is in large excess and thus does not effect the dissociation of pyridine.
