Question

If a sample of barium contains 2.3 x 1023 atoms of barium, how many grams of barium are in the sample? A) 0.38 g. B) 2.62 g. C) 52.4 g. D) 359.5 g.

Answer 1

n= number of molecules
n= 2.3x10^23/6.022x10^23
= 0.381 mol

Now,
M= molar mass in g/mol
m= mass in grams
m=nxM
=0.381 molx137 g/mol
= 52.197g

So, the correct answer should be C

Answer 2

The grams of barium that are in 2.3 x 10^23 atoms of barium is 52.4 g (answer C)

calculation

mass = moles of Ba x molar mass of Ba

molar mass of Ba from periodic table= 137.3 g/mol

• use the Avogadro's law constant to calculate the moles of Barium

that is 1 mole = 6.02 x 10^23 atoms

? moles = 2.3 x 10^23 atoms

by cross multiplication

=(1 mole x 2.3x 10^23 atoms) / 6.02 x10^23 atoms)= 0.382 moles

mass is therefore = 137.3 g/mol x 0.382 mol = 52.4 ( answer C)