A compound made up of two elements A and B has `A = 70%, B = 30%`. Their relative number of moles in the compound is 1.25 and 1.88, calculate :
Atomic masses of the elements A and B

Answer

To calculate the atomic masses of elements A and B based on the given percentages and relative number of moles, we can follow these steps:

### Step 1: Understand the formula
The formula to calculate the atomic mass of an element based on its percentage in a compound and the relative number of moles is:

\[ \text{Atomic Mass} = \frac{\text{Percentage of Element}}{\text{Relative Number of Moles}} \]

### Step 2: Calculate the atomic mass of element A
Given:
- Percentage of A = 70%
- Relative number of moles of A = 1.25

Using the formula:

\[ \text{Atomic Mass of A} = \frac{70}{1.25} \]

Calculating this:

\[ \text{Atomic Mass of A} = \frac{70}{1.25} = 56 \text{ g/mol} \]

### Step 3: Calculate the atomic mass of element B
Given:
- Percentage of B = 30%
- Relative number of moles of B = 1.88

Using the formula:

\[ \text{Atomic Mass of B} = \frac{30}{1.88} \]

Calculating this:

\[ \text{Atomic Mass of B} = \frac{30}{1.88} \approx 15.96 \text{ g/mol} \]

Since atomic masses are usually reported as whole numbers, we round this to:

\[ \text{Atomic Mass of B} \approx 16 \text{ g/mol} \]

### Step 4: Present the final results
Thus, the atomic masses of the elements are:
- Atomic mass of A = 56 g/mol
- Atomic mass of B = 16 g/mol

### Final Answer:
- Atomic mass of A = 56 g/mol
- Atomic mass of B = 16 g/mol