Which sample contains the same number of atoms as 175.0 g of cadmium (Cd)?
A) 225 g Pb
B) 175 g Hg
C) 307 g Au
D) 142 g Ir
E) 305 g Sn

Question

Quizplus · Accepted Answer

The molar mass of cadmium is approximately 112.4 g/mol. Therefore, 175.0 g of cadmium contains 175.0 g / 112.4 g/mol = 1.556 mol. One mole of any element contains 6.022 x 10^23 atoms (Avogadro's number). Therefore, 1.556 mol of cadmium contains 1.556 x 6.022 x 10^23 = 9.37 x 10^23 atoms. Checking each option, we find that only 307 g of gold (Au) contains the same number of atoms as 175.0 g of cadmium.

Which Sample Contains the Same Number of Atoms as 175