Question

Percentage purity of a sample of gold is 85%. How many atoms of gold are present in its 1 gram sample? (Atomic mass of gold = 197 u)

• A. $2.6\times {10}^{21}$
• B. $2.6\times {10}^{23}$
• C. $3.0\times {10}^{21}$
• D. $4.5\times {10}^{20}$

Answer 1

The correct option is A

$2.6\times {10}^{21}$

85% gold in 1 gram sample

0.85g gold is present in 1 gram sample

197g of gold = 6.022$\times$ ${10}^{23}$ atoms of gold

0.85g of gold = $\frac{6.022}{197}\times 0.85=2.6\times {10}^{21}$