Percentage of isotopes in 35/17 Cl and 37/17 Cl with the molar mass of chlorine as 35.5g and the mass of each nucleon to be 1.0000 amu

The abundance of 35/17 Cl is 75% and 25% of 37/17Cl

Explanation:

The molar mass of an atom is defined as the sum of the masses of each isotope times its abundance, that is:

35.5amu = 35amu*X + 37amu*Y (1)

Where X is the abundance of the 35/17Cl and Y the abundance of 37/17 Cl

As there are just these 2 isotopes and the abundances of both isotopes = 1:

X + Y = 1 (2)

Replacing (2) in (1):

35.5 = 35X + 37(1-X)

35.5 = 35X + 37 - 37X

-1.5 = -2X

X = 0.75 = 75%

And Y = 100-75% = 25%

c- cold periods in earth's history during which glaciers covered much of the surface.

explanation: