How many grams of NaOH will be needed to prepare 250 mL of 0.1 M solution-

Options

A. 1 g
B. 10 g
C. 4 g
D. 6 g

Answer

To determine how many grams of NaOH are needed to prepare 250 mL of a 0.1 M solution, we can follow these steps:

### Step 1: Understand the relationship between molarity, moles, and volume.
Molarity (M) is defined as the number of moles of solute per liter of solution. The formula is:
\[ M = \frac{\text{Number of moles of solute}}{\text{Volume of solution in liters}} \]

### Step 2: Convert the volume from mL to L.
Given that the volume of the solution is 250 mL, we need to convert this to liters:
\[ \text{Volume in liters} = \frac{250 \text{ mL}}{1000} = 0.250 \text{ L} \]

### Step 3: Calculate the number of moles of NaOH.
Using the molarity formula, we can rearrange it to find the number of moles:
\[ \text{Number of moles of NaOH} = M \times \text{Volume in liters} \]
Substituting the values we have:
\[ \text{Number of moles of NaOH} = 0.1 \, \text{M} \times 0.250 \, \text{L} = 0.025 \, \text{moles} \]

### Step 4: Find the molar mass of NaOH.
The molar mass of NaOH can be calculated by adding the atomic masses of its constituent elements:
- Sodium (Na): 23 g/mol
- Oxygen (O): 16 g/mol
- Hydrogen (H): 1 g/mol

Thus, the molar mass of NaOH is:
\[ \text{Molar mass of NaOH} = 23 + 16 + 1 = 40 \, \text{g/mol} \]

### Step 5: Calculate the mass of NaOH needed.
Now, we can use the number of moles and the molar mass to find the mass:
\[ \text{Mass of NaOH} = \text{Number of moles} \times \text{Molar mass} \]
Substituting the values:
\[ \text{Mass of NaOH} = 0.025 \, \text{moles} \times 40 \, \text{g/mol} = 1 \, \text{g} \]

### Final Answer:
To prepare 250 mL of a 0.1 M NaOH solution, you will need **1 gram of NaOH**.

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