Question

1)Chlorine has two stable isotopes. The first isotope has a mass number 35 and is present 75.77% of the time. The second isotope has a mass number of 37. Calculate their molar mass of Chlorine.

2) what type of question is this?

3) Explain background information?

4)What Info do you need to solve it?

5)Solve question giving step wise advice.

6)Give example it could be rewrttten?

Answer 1

1. chlorine molar mass is 35.453 or generally 35.5 u

2. This question is about calculating the average molar mass of atoms which have isotopes.

3.  We know that Isotopes are atoms with the same number of protons but that have a different number of neutrons. The atomic number A, is equal to the number of protons and the atomic mass Z, is the sum of protons and neutrons, Isotopes will have same atomic number but different mass. A the abundence of isotopes are different, the atomic molecular weight or molar mass will depend on their abbundence.

4. To know the molar mass of isotopes, we should know the natural abundence of isotopes and their respective mass numbers also.

5. Cl-35 has molar mass is 35 (17 protons+18 neutrons) and natural abundence near 75% or 0.75 and Cl-37 has molar mass 37 (17 protons +20 neutrons) and available is 25% or 0.25.

average atomic mass of atom = (isotope molar mass * natural abundence)

average atomic mass of chlorine = = [34.9689x 0.757 + 36.9659x 0.242]/(0.757+0.242) =35.4521 or nearly 35.5 u.

6.

Same type of calculation valid for other isotoes

Example Br isotopes. Br have two isotopes, Br-79, Br-81 with natural availability near 1:1. The molar mass of Br considered as avg of boththe isotopes and it is 80.