# For drivers in the UK, the legal limit of the concentration of ethanol (molar mass 46 g mol-1) in the blood mg per 100 cm^3. What is equivalent to a concentration of?

Oct 8, 2016

In England and Wales, the blood alcohol limit is $80 \cdot m g \text{ per 100}$ $m L$ of blood,........

#### Explanation:

And in Scotland (where there are notable dipsos!) it is $50 \cdot m g \text{ per 100}$ $m L$ of blood.

And thus is molar terms, we simply turn the mass into a molar quantity:

$\text{Molarity}$ $=$ $\text{Moles of solute"/"Volume of solution}$

$=$ $\frac{80 \cdot \cancel{m g} \times {10}^{-} 3 \cdot \cancel{g} \cdot \cancel{m {g}^{-} 1}}{46 \cdot \cancel{g} \cdot m o {l}^{-} 1} \times \frac{1}{100 \cdot \cancel{m L} \times {10}^{-} 3 \cdot L \cdot \cancel{m {L}^{-} 1}}$

$=$ $0.017 \cdot m o l \cdot {L}^{-} 1$ in England.