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A sample of gold (Au) has a mass of 35.12 g..

ACalculate the number of moles of gold (Au) in the sample. .. .
BCalculate the number of atoms of gold (Au) in the sample

Verified Answer :

Willchemistry
AMolar mass gold ( Au) = 196.96 g/mol

1 mole Au ----------- 196.96 g
? moles Au ---------- 35.12 g

35.12 x 1 / 196.96

= 0.178 moles of Au
_____________________________

b) 196.96 g --------------- 6.02x10²³ atoms
    35.12 g ---------------- ( atoms ? )

35.12 x ( 6.02x10²³) / 196.96

2.114x10²⁵ / 196.96

= 1.07x10²³ atoms
_____________________________________________

Answer:

a) 0.1783 moles of gold.

b) \(1.074\times 10^{23}\) atoms of gold.

Explanation:

Mass of gold sample = 35.12 g

Atomic mass of gold = 197 g/mol

Moles of compound = \(\frac{\text{mass of the compound}}{\text{molar mass of compound}}\)

a) Moles of gold :'\(\frac{35.12 g}{197 g/mol}=0.1783 mol\)

1 mole = \(6.022\times 10^{23}\) atoms. molecule

b) Number of gold atoms in 0.1783 moles:

\(=0.1783\times 6.022\times 10^{23}=1.074\times 10^{23} atoms\)

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