To calculate the mass of solute (NaOH) needed to prepare 25 mL of a 0.50 M NaOH solution, you can follow these steps:

Step 1: Calculate the number of moles of NaOH needed.

Use the formula: $\text{{Moles of NaOH}} = \text{{Molarity}} \times \text{{Volume (in liters)}}$

Given:

• Molarity ($M$) = 0.50 M
• Volume ($V$) = 25 mL = 0.025 L

$\text{{Moles of NaOH}} = 0.50 \, \text{M} \times 0.025 \, \text{L} = 0.0125 \, \text{moles}$

Step 2: Calculate the mass of NaOH needed.

Use the formula: $\text{{Mass}} = \text{{Moles}} \times \text{{Molar Mass of NaOH}}$

The molar mass of NaOH is calculated as follows:

• Na: 22.99 g/mol
• O: 16.00 g/mol
• H: 1.01 g/mol

$\text{{Molar Mass of NaOH}} = 22.99 + 16.00 + 1.01 = 40.00 \, \text{g/mol}$

Now, calculate the mass: $\text{{Mass}} = 0.0125 \, \text{moles} \times 40.00 \, \text{g/mol} = 0.50 \, \text{g}$

Final Answer:

You need 0.50 grams of NaOH to prepare 25 mL of a 0.50 M NaOH solution.

Would you like more details or have any questions?

Here are some related questions you might consider:

1. How would you prepare a 1.0 M NaOH solution?
2. What is the process for diluting a solution to a lower concentration?
3. How does temperature affect the solubility of NaOH in water?
4. How can you determine the concentration of an unknown NaOH solution?
5. What safety precautions should be taken when handling NaOH?

Tip: Always ensure to measure the volume accurately when preparing a solution to achieve the desired concentration.