Question

How to find the concentration of NaOH in a titration problem involving H2SO4

Answer 1

To find the concentration of NaOH in a titration problem involving sulfuric acid (H₂SO₄), you'll typically follow these steps:

### 1. **Write the Balanced Chemical Equation:**

First, write the balanced equation for the reaction between sodium hydroxide (NaOH) and sulfuric acid (H₂SO₄):

\[
2 \, \text{NaOH} + \text{H₂SO₄} \rightarrow \text{Na₂SO₄} + 2 \, \text{H₂O}
\]

This indicates that 2 moles of NaOH react with 1 mole of H₂SO₄.

### 2. **Record Your Data:**

Collect the following information from the experiment:
- The volume (in liters) of H₂SO₄ solution used in the titration.
- The concentration (in moles per liter, M) of the H₂SO₄ solution used.
- The volume (in liters) of NaOH solution required to reach the endpoint of the titration.

### 3. **Calculate Moles of H₂SO₄:**

Using the concentration and the volume of the H₂SO₄ solution, calculate the moles of H₂SO₄:

\[
\text{Moles of H₂SO₄} = \text{Concentration of H₂SO₄ (M)} \times \text{Volume of H₂SO₄ (L)}
\]

### 4. **Use Stoichiometry to Find Moles of NaOH:**

From the balanced equation, you know that 2 moles of NaOH react with 1 mole of H₂SO₄. Therefore, you can find the moles of NaOH:

\[
\text{Moles of NaOH} = 2 \times \text{Moles of H₂SO₄}
\]

### 5. **Calculate Concentration of NaOH:**

Finally, use the volume of NaOH solution used during the titration to find its concentration:

\[
\text{Concentration of NaOH (M)} = \frac{\text{Moles of NaOH}}{\text{Volume of NaOH (L)}}
\]

### Example Problem:

**Given:**
- Volume of H₂SO₄ = 0.025 L
- Concentration of H₂SO₄ = 0.1 M
- Volume of NaOH = 0.015 L

**Steps:**

1. Calculate the moles of H₂SO₄:

\[
\text{Moles of H₂SO₄} = 0.1 \, \text{M} \times 0.025 \, \text{L} = 0.0025 \, \text{moles}
\]

2. Calculate the moles of NaOH:

\[
\text{Moles of NaOH} = 2 \times 0.0025 \, \text{moles} = 0.005 \, \text{moles}
\]

3. Calculate the concentration of NaOH:

\[
\text{Concentration of NaOH} = \frac{0.005 \, \text{moles}}{0.015 \, \text{L}} \approx 0.333 \, \text{M}
\]

So, the concentration of the NaOH solution is approximately 0.333 M.