Question

If a sample of pure sodium has a mass of 8.2 grams and sodium has an average atomic mass of 22.99 g/mol, how many sodium atoms are there in the sample?

3.21 x 1021 atoms
2.15 x 1023 atoms
1.69 x 1024 atoms
1.13 x 1026 atoms

Answer 1

8.2 grams = 1 mol
Na ________
22.99 grams

First multiply the value of 8.2 to 1. Then divide by the value of 22.99 to determine the number of moles of sodium present in the 8.2 gram sample.

Then use the following equation to solve for sodium atoms.

Number of moles of Na • Avogadro Number = Number of sodium atoms.

0.3566782 • (6.02 X 10^23). = 2.1472 X 10 ^ 23. Or 2.15 X 10 ^ 23.

The answer is the second option - 2.15 X 10 ^ 23.