Aqueus solution of borax acts as a buffer because

Options

A. It contains tribasic acid and strong base.
B. It contains weak acid and its salt with strong base.
C. It contains number of neutral water molecules.
D. None of the above

Explanation

To understand why an aqueous solution of borax acts as a buffer, we can break down the explanation into several steps:

### Step 1: Identify Borax
Borax is a compound with the formula Na2B4O7·10H2O. It is a salt of boric acid (H3BO3) and sodium hydroxide (NaOH).

### Step 2: Understand Buffer Solutions
A buffer solution is one that resists changes in pH when small amounts of acid or base are added. It typically consists of a weak acid and its conjugate base or a weak base and its conjugate acid.

### Step 3: Components of Borax Solution
When borax is dissolved in water, it dissociates to form sodium ions (Na+) and borate ions (B(OH)4−). The borate ions can react with water to form boric acid (H3BO3), which is a weak acid.

### Step 4: Reaction in Aqueous Solution
The reaction can be summarized as follows:
\[ \text{B(OH)}_4^- + \text{H}_2\text{O} \rightleftharpoons \text{H}_3\text{BO}_3 + \text{OH}^- \]
This equilibrium allows the solution to resist changes in pH.

### Step 5: Conclusion
Thus, the aqueous solution of borax acts as a buffer because it contains a weak acid (boric acid) and its salt (sodium borate) with a strong base (sodium hydroxide). This combination allows it to maintain a relatively stable pH when acids or bases are added.

### Final Answer
An aqueous solution of borax acts as a buffer because it contains a weak acid (boric acid) and its salt with a strong base (sodium borate).

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