The relative atomic mass of boron 10.2.if the element occurs in two isotopic forms, boron-10 and boron-11 ,what are their geometrical abundances?

Find the abundance of each isotope.

Let y/100 = the abundance of copper-10
and (100 - y)/100 = the abundance of copper-11

10.2 = (y/100 x 10) + [(100 - y)/100 x 11] 
10.2 = 10y/100 + 1100/100 - 11y/100 
1020 = 10y + 1100 - 11y 
-80 = -y 
y = 80

Abundance of boron-10 = 10/100 = 10%

Abundance of boron-11 = 100 - 10 = 90%

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.

fe 55.85 g/mol and h2o 18.02 g/mol.