Question

how many O atoms are present in a 7.07 ng sample of quinine, C20H24O2N2? Note: 1 ng is one nanogram.

Answer 1

Question #64726, Chemistry / Other

How many O atoms are present in a 7.07 ng sample of quinine, $C_{20}H_{24}O_2N_2$? Note: 1 ng is one nanogram.

Answer:

1 ng = $10^{-9}$ g

7.07 ng = $7.07 \times 10^{-9}$ g

$$n(\text{quinine}) = \frac{m(\text{quinine})}{M(\text{quinine})}$$ $$n(\text{quinine}) = \frac{7.07 \times 10^{-9} \text{ g}}{324.42 \text{ g/mol}} = 2.17 \times 10^{-11} \text{ mol}$$

$N(\text{quinine}) = 2.17 \times 10^{-11} \text{ mol} \times 6.02 \times 10^{23} \text{ mol}^{-1} = 1.312 \times 10^{13} \text{ molecules}$

Each quinine molecule contains 2 O atoms. Thus:

$$N(O) = 1.312 \times 10^{13} \times 2 = 2.624 \times 10^{13} \text{ atoms}$$

Answer provided by https://www.AssignmentExpert.com