Question

1. Lemon juice is a weak acid. It has a [H+] of 5.0 × 10^-2 M. What is the pH of lemon juice?

A. 1.0
B. 1.3
C. 5.0
D. 7.5 2. Water can act as both an acid and a base in an ionization reaction to form H+ and OH- ions. What is this phenomenon called?
A. neutralization
B. acid dissociation
C. base dissociation
D. self-ionization 3. A solution of vinegar and water has a pH of 6.2. What type of solution is this?
A. acidic
B. basic
C. neutral 4. Hydrochloric acid (HCl) and acetic acid (HC2H3O2) are both acids. HCl completely dissociates in water, while HC2H3O2 does not. Which of the following statements best describes these two acids?
A. HCl is a strong acid; HC2H3O2 is a strong acid.
B. HCl is a weak acid; HC2H3O2 is a weak acid.
C. HCl is a strong acid; HC2H3O2 is a weak acid.
D. HCl is a weak acid; HC2H3O2 is a strong acid.
5. Pyridine is a weak base with the formula C5H5N. Pyridine reacts with water according to the following equation: C5H5N + H2O ---> C5H5NH+ + OH-. What is the formula for the dissociation constant for this base?
A. Kb = [OH-][C5H5NH+]/[C5H5N]
B. Kb = [H+][CO2H-]/[C5H5N]
C. Kb = [C5H5N]/[OH-][CO2H-]
D. Kb = [C5H5N][CO2H-]/[OH-]

Answer 1

Answer: 1. B. 1.3

2. D. self-ionization

3. A. acidic

4. HCl is a weak acid;
`CH_3COOH` is a weak acid.

5. A.
`K_b=([OH^-][C_5H_5NH^+])/([C_5H_5N])`

Explanation:

1. pH is the negative logarithm of hydrogen ion concentration.

`pH=-log[H^+]`

Given:
`[H^+]=5.0* 10^(-2)=0.05`

`pH=-log[0.05M]=1.30`

2. An acid is a substance which donates
`H^+` ions when dissolved in water.

A base is a substance which donates
`OH^-` ions when dissolved in water.

Thus as water ionizes to give both ions, it acts as both acid and base.

`H_2O\rightarrow H^++OH^-` 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.

`HCl\rightarrow H^++Cl^-`

Weak acids are those acids which do not undergo complete dissociation when dissolved in water.

`CH_3COOH\rightleftharpoons CH_3COO^-+H^+`

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.

`C_5H_5N+H_2O\rightarrow C_5H_5NH^++OH^-`

`K_b=([OH^-][C_5H_5NH^+])/([C_5H_5N])`

The concentration of water is ignored as it is in large excess and thus does not effect the dissociation of pyridine.

Answer 2

I am pretty sure these answer wil help you! Regards.

1) B. 1.3
2) D. self-ionization
3) B. basic
4) C. HCl is a strong acid; HC2H3O2 is a weak acid.
5) Kb = [OH-][C5H5NH+]/[C5H5N]