How many grams of NaOH are present in 250 mL of 0.5 M NaOH solution?

Options

A. 7.32 g
B. 3.8 g
C. 5g
D. 0.5 g

Explanation

To find out how many grams of NaOH are present in 250 mL of a 0.5 M NaOH solution, we can follow these steps:

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

### Step 2: Convert Volume from mL to Liters
Since the volume is given in milliliters (mL), we need to convert it to liters (L).
\[ 250 \, \text{mL} = \frac{250}{1000} \, \text{L} = 0.250 \, \text{L} \]

### Step 3: Calculate the Number of Moles of NaOH
Now, we can use the molarity and the converted volume to find the number of moles of NaOH.
\[ \text{Number of moles} = 0.5 \, \text{M} \times 0.250 \, \text{L} = 0.125 \, \text{moles} \]

### Step 4: Find the Molar Mass of NaOH
Next, we need to find the molar mass of NaOH. The molar mass is calculated by adding the atomic masses of sodium (Na), oxygen (O), and hydrogen (H):
- Sodium (Na) = 23 g/mol
- Oxygen (O) = 16 g/mol
- Hydrogen (H) = 1 g/mol

So, 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
Finally, we can find the mass of NaOH using the number of moles and the molar mass:
\[ \text{Mass} = \text{Number of moles} \times \text{Molar mass} \]
\[ \text{Mass} = 0.125 \, \text{moles} \times 40 \, \text{g/mol} = 5 \, \text{grams} \]

### Final Answer
Thus, the mass of NaOH present in 250 mL of 0.5 M NaOH solution is **5 grams**.

---