Question

Calculate the mass, in grams, of Avogadro's number of calcium atoms.

Answer 1

Required data to solve this problem:

• Avogadro's number: 6.022x10²³
• Avogadro's number = 1 mole
• Molar mass of calcium: 40.078 g/mol

This is a unit analysis problem wherein we are given Avogadro's number and we're trying to output a mass in grams.  Molar mass can be used as a conversion factor, since molar mass is in units of grams per mole.  Since we know that Avogadro's number is equal to one mole, we can set up a unit analysis to go from Avogadro's number to grams, with moles as the middleman, so to speak.

$\frac{6.022x10^{23} atoms}{1mol Ca} (\frac{1mol Ca}{40.078g Ca} )=1.503x10^{22} g Ca$

The moles cancel and the answer is Avogadro's number divided by 40.078.

Answer:

1.503x10²² grams