Answer to Question #87544 in General Chemistry for Ellis

Question

An aspirin tablet contains 0.325g of acetylsalicylic acid (C9H8O4).

How many acetylsalicylic acid molecules does it contain?

What is the total number of atoms in that sample?

Answer 1

(i) Find number of moleculs of $C_9H_8O_4$

$n = \frac{m}{M}$

$n(C_9H_8O_4) = \frac{0.325 g}{180.16 \frac{g}{mol}} = 0.00180 mol$

$N = N_A\times n$

$N(C_9H_8O_4) = 6.022\times 10^{23} mol^{-1} \times 0.00180 mol = 1.086\times10^{21} molecules$

(ii) find total number of atoms:

As 1 molecule of $C_9H_8O_4$ contains 9+8+4 = 21 atoms, then

$N_{total}(atoms) = 21\times N(C_9H_8O_4) = 21\times 1.086\times10^{21} = 2.281\times 10^{22} atoms$