# What molar quantity of HCl is present in a 23.6*cm^3 volume of 0.1*mol*L^-1 concentration?

You need to quote the $\text{density}$, $\rho$, of the acid solution..........
As a matter of fact, the density of this (fairly dilute) acid would be very close to that of water, i.e. $\rho = 1 \cdot g \cdot c {m}^{-} 3$. However, we need it to get the volume of the acid............and THEN we can calculate the number of moles this mass of solution contains quite precisely.