Question

The chemical formula of aspirin is C9H8O4. What is the mass of 0.40 mol
of aspirin?​

Answer 1

`\boxed {\boxed {\sf About \ 72 \ grams }}`

Step-by-step explanation:

To convert from moles to grams, we must use the molar mass (also known as the gram formula mass).

First, look up the molar masses of the elements in the formula.

• C: 12.011 g/mol
• H: 1.008 g/mol
• O: 15.999 g/mol

Next, multiply by the subscript, because it tells us the number of atoms of each element in the formula.

• C₉: 4(12.011 g/mol)= 108.099 g/mol
• H₈: 8(1.008 g/mol)= 8.064 g/mol
• O₄: 4(15.999 g/mol)= 63.996 g/mol

Add the values.

• 108.099 + 8.064+63.996=180.159 g/mol

Use this molar mass as a ratio.

`\frac {180.159 \ g \ C_9H_8O_4}{1 \ mol \ C_9H_8O_4}`

Multiply by the given number of moles, 0.40

`0.40 \ mol \ C_9H_8O_4 *\frac {180.159 \ g \ C_9H_8O_4}{1 \ mol \ C_9H_8O_4}`

The units moles of aspirin cancel.

`0.40 *\frac {180.159 \ g \ C_9H_8O_4}{1 }`

`72.0636 \ g \ C_9H_8O_4`

The original number of moles has 2 sig figs (4 and 0), so answer must have the same. For the number we calculated, it is the ones place. The 0 in the tenth place tells us to leave the 2.

`72 \ g`