CGPET 2015 Solved Paper

Given, concentration of SrCl2=10−3 mol\% concentration is in percentage so that take total 100‌mL of solution.Number of moles of NaCl=100−3 moles of SrCl2Moles of SrCl2 is very negligible as compare to total moles so percentage always taken as 100 so that
1 mole of NaCl is dipped with =

10−3

100

mole of SrCl2
=10−5‌mole‌of‌SrCl2
So, cation vacancies per mole of NaCl=10−5‌mol
Since, 1‌mole=6.022×1023 particles
So, cation vacancies per mole of NaCl
=10−5×6.022×1023
=6.022×1018