Question

The source of bitterness in dark chocolate is the compound theobromine, an alkaloid present in cocoa beans. In a sample of dark chocolate there are 6.52 x 10^20 molecules of theobromine present. How many milligrams of theobromine are present in the sample? The molecular formula for theobromine is C7H8N4O2.

Answer 1

$$n=\frac{N}{N_A}= \frac{6.52\times10^{20}}{6.022\times 10^{23}}=1.08\times10^{-3}mol$$

$$m=M\times n$$

$M(C_7H_8N_4O2)=180.164 \frac{g}{mol}$

$$m(C_7H_8N_4O_2)= 180.164\times1.08\times10^{-3}= 0.195 g =195 mg$$