75% of Cl atoms have a mass number of 35, whilst the remaining 25% have a mass number of 38. What is the relative atomic mass of chlorine? Give an exact answer.

## Step 1:The relative atomic mass of an element is the weighted average of the atomic masses of its isotopes, based on their natural abundances.## Step 2:To calculate the relative atomic mass of chlorine, we need to multiply the mass number of each isotope by its relative abundance (as proportions of 1) and sum the results.### **Formula:** ## Step 3:Substituting the given values into the formula: ## Step 4:Perform the calculations: ## Step 5:Sum the results: