If pH of a 0.01N monobasic acid is 2.0, the acid must be

Options

A. strong
B. weak
C. same
D. different

Answer

To determine the nature of the monobasic acid given that the pH of a 0.01N solution is 2.0, we can follow these steps:

### Step 1: Understand the relationship between pH and [H⁺]
The pH of a solution is defined as:
\[ \text{pH} = -\log[H^+] \]
Where \([H^+]\) is the concentration of hydrogen ions in moles per liter.

### Step 2: Calculate the concentration of [H⁺]
Given that the pH is 2.0, we can calculate \([H^+]\):
\[ 2.0 = -\log[H^+] \]
Taking the antilogarithm:
\[ [H^+] = 10^{-2} \, \text{M} = 0.01 \, \text{M} \]

### Step 3: Relate the concentration of the acid to [H⁺]
Since the acid is monobasic, it will dissociate completely in solution, meaning that the concentration of the acid will equal the concentration of \([H^+]\). Therefore, if the concentration of \([H^+]\) is 0.01 M, the concentration of the acid must also be 0.01 M.

### Step 4: Identify the type of acid
Since the concentration of the acid (0.01 M) is equal to the concentration of \([H^+]\) produced, this indicates that the acid is a strong acid. Strong acids completely dissociate in solution, leading to a direct correlation between the concentration of the acid and the concentration of hydrogen ions.

### Conclusion
Since the pH of the 0.01N monobasic acid is 2.0, the acid must be a strong acid.