Question

Tia has a sample of pure gold (Au). She weighed the sample and the result was 35.9 grams. Tia wants to determine the number of atoms in the sample. Calculate the number of atoms in 35.9 g of pure gold.

Answer 1

First, find moles of gold given the mass of the sample:
(35.9g Au)/(197.0g/mol Au) = 0.182mol Au

Second, multiply moles of Au by Avogrado's number:
(0.182mol)(6.02 x10^23)= 1.10x10^23 atoms Au

Answer 2

Answer: $1.09\times 10^{23atoms$ of gold.

Explanation: To calculate the moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\textMolar mass}}$

For gold

Mass of gold given = 35.9 g

Molar mass of gold = 197 g/mol

Putting values in above equation, we get:

$\text{Moles of gold}=\frac{35.9g}{197g/mol}=0.18mol$

According to Avogadro's law, 1 mole of every substance contains avogadro's number $(6.023\times 10^{23})$ of particles.

Thus 0.18 moles of gold will contain=$\frac{6.023\times 10^{23}}{1}\times 0.18=1.09\times 10^{23}$ atoms of gold.