A solution is prepared by adding 2g of substance A to 18g of water. The mass percent of the solute.

Options

A. 10
B. 20
C. 40
D. 25

Explanation

To find the mass percent of the solute in the solution, we can follow these steps:

### Step 1: Identify the mass of the solute and the solvent
- The mass of the solute (substance A) is given as 2 g.
- The mass of the solvent (water) is given as 18 g.

### Step 2: Calculate the total mass of the solution
- The total mass of the solution is the sum of the mass of the solute and the mass of the solvent.

\[ \text{Mass of solution} = \text{Mass of solute} + \text{Mass of solvent} = 2 \, \text{g} + 18 \, \text{g} = 20 \, \text{g} \]

### Step 3: Use the mass percent formula
- The formula for mass percent is:

\[ \text{Mass percent of solute} = \left( \frac{\text{Mass of solute}}{\text{Mass of solution}} \right) \times 100 \]

### Step 4: Substitute the values into the formula
- Now we can substitute the known values into the formula:

\[ \text{Mass percent of solute} = \left( \frac{2 \, \text{g}}{20 \, \text{g}} \right) \times 100 \]

### Step 5: Calculate the mass percent
- Performing the calculation:

\[ \text{Mass percent of solute} = \left( \frac{2}{20} \right) \times 100 = 0.1 \times 100 = 10\% \]

### Conclusion
- The mass percent of the solute (substance A) in the solution is **10%**.

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