Question

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?

Answer 1

In England and Wales, the blood alcohol limit is `80*mg" per 100"` `mL` of blood,........

Explanation:

And in Scotland (where there are notable dipsos!) it is `50*mg" per 100"` `mL` of blood.

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

`"Molarity"` `=` `"Moles of solute"/"Volume of solution"`

`=` `(80*cancel(mg)xx10^-3*cancel(g)*cancel(mg^-1))/(46*cancel(g)*mol^-1)xx1/(100*cancel(mL)xx10^-3*L*cancel(mL^-1))`

`=` `0.017*mol*L^-1` in England.