Answer:
75% of Cl-35 and 25% of Cl-37
Explanation:
Equation to find the mass number of an element. repeat the brackets for however many isotopes it has.
[tex] \frac{(abundance \: \times \: mr) \: + \: (abundance \: \times \: mr)}{100} [/tex]
[tex] \frac{(75 \times 35) + (25 \times 37)}{100} = 35.5[/tex]
You can try guess it because 35.5 is closer to 35 than 37 so it has a higher abundance of Cl-35
