How many atoms of calcium are in 80.0 grams of calcium?

Answer 1

You need to know the molar mass for Ca which is: 40.078 g/mol and avrogadros # or whatever which is: 6.022 x 10^23

So:

80.0g Ca x (1 mol Ca / 40.078 g Ca) = 1.996 mol Ca (this eliminated grams)

1.996 mol Ca x (6.022 x 10^23 atoms / 1 mol Ca) = 1.202 x 10^24 atoms of calcium

Just remember the fraction 6.022 x 10^23 atoms / 1 mol ! It's the same thing so you can flip it!

Answer 2

First find how many moles are in 80.45g of Mg. The molecular weight of Mg is 24.305g (found on the Periodic Table) so there is one mol per 24.305g of Mg. 80.45/24.305=3.310 mol Mg

Once you know the moles of the sample you can use Avagadro's number to find the number of atoms. 6.02x10^23(3.310)=1.993x10^24 atoms of Mg

Answer 3

80.45 g (6.02 x 1023 at / 24.31 g) = 1.99 x 1024atoms

Answer 4

Moles = mass/ relative Atomic Mass of Mg

= 80.45/ 24.3

= 3.31 moles (to 3 significant figures)

Answer 5

roughly half a mole or 3.01E23 atoms. This is too easy! Didn't even need a calculator, did it in my head.

Answer 6

1 gram of magnesium contain 0,2477.10e23 atoms.

Answer 7

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