Equal volumes of hydrochloric acid and sodium hydroxide solutions of same concentration are mixed and the pH of the resulting solution is checked with a pH paper . What would be the colour obtained ?

Options

A. Red
B. Yellow
C. Yellowish green
D. Blue

Explanation

To solve the question step by step, we can follow this reasoning:

### Step 1: Understand the Reaction
When equal volumes of hydrochloric acid (HCl) and sodium hydroxide (NaOH) are mixed, they undergo a neutralization reaction. The chemical equation for this reaction is:
\[ \text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O} \]
This shows that hydrochloric acid reacts with sodium hydroxide to produce sodium chloride (table salt) and water.

**Hint:** Remember that neutralization reactions produce water and a salt.

### Step 2: Concentration and Volume
Since the question states that the solutions are of the same concentration and equal volumes, the amount of HCl will completely neutralize the amount of NaOH. This means that there will be no excess acid or base in the solution.

**Hint:** Equal volumes and equal concentrations mean that the moles of acid and base are equal.

### Step 3: Determine the Nature of the Resulting Solution
After the neutralization, the resulting solution contains only the salt (NaCl) and water. The pH of pure water is 7, which is neutral. Since NaCl is a neutral salt formed from a strong acid (HCl) and a strong base (NaOH), the resulting solution will also be neutral.

**Hint:** The pH of a neutral solution is typically around 7.

### Step 4: Checking the pH with pH Paper
When the pH of the resulting solution is checked with pH paper, we need to look at the color that corresponds to a neutral pH. Typically, pH paper shows a yellowish-green color at a neutral pH (around 7).

**Hint:** Familiarize yourself with the color scale of pH paper; yellowish-green indicates neutrality.

### Conclusion
Therefore, when equal volumes of hydrochloric acid and sodium hydroxide solutions of the same concentration are mixed, the resulting solution will have a pH that corresponds to a yellowish-green color on pH paper.

**Final Answer:** The color obtained will be yellowish-green.