`mass%` of an element =A x 100/molar mass of the compound` here A refers to

Options

A. atoms of the elements in the compound
B. mol of that element in that compound
C. mass of that element in the compond
D. `%` of that element in the compound

Answer

To solve the question regarding the formula for calculating the mass percentage of an element in a compound, we can break it down into clear steps:

### Step-by-Step Solution:

1. **Understand the Formula**: The formula given is:
\[ \text{mass\% of an element} = \frac{A \times 100}{\text{molar mass of the compound}} \]
Here, \( A \) represents the mass of the element in the compound.

2. **Identify the Components**:
- **A**: This is the mass of the specific element you are interested in within the compound.
- **Molar Mass of the Compound**: This is the total mass of one mole of the compound, which can be calculated by adding the atomic masses of all the atoms in the compound.

3. **Calculate the Mass of the Element**: To find \( A \), you need to know how many atoms of the element are present in the compound and their respective atomic masses. For example, if the compound is \( AB_2 \) (where \( A \) is one element and \( B \) is another), you would calculate the mass of \( A \) based on its atomic mass and the number of \( A \) atoms in the formula.

4. **Calculate the Molar Mass of the Compound**:
- For \( AB_2 \), the molar mass would be calculated as:
\[ \text{Molar Mass} = \text{Atomic Mass of A} + 2 \times \text{Atomic Mass of B} \]

5. **Plug Values into the Formula**: Once you have both \( A \) (mass of the element) and the molar mass of the compound, substitute these values into the formula to find the mass percentage.

6. **Final Calculation**: Perform the calculation to find the mass percentage of the element in the compound.

### Example:
If \( A \) (mass of element A in the compound) is 10 g and the molar mass of the compound \( AB_2 \) is 50 g/mol, then:
\[ \text{mass\% of A} = \frac{10 \times 100}{50} = 20\% \]