# What is the concentration of a 1*mL volume of a solution of 37% HCl (rho=1.18*g*mL^-1) that is diluted to 3.50*mL?

Now, I ASSUME that you have diluted a $1 \cdot m L$ volume of 37% $\text{w/w}$ hydrochloric solution to $3.5 \cdot m L$. In order to calculate this problem you need the density of the conc. acid, which is $\rho = 1.18 \cdot g \cdot m {L}^{-} 1$. These data SHOULD have been included with the question.
So we want $\text{moles of solute"/"volume of solution}$
=((1*mLxx1.18*g*mL^-1xx37%)/(36.46*g*mol^-1))/(3.5*cancel(mL)xx10^-3*L*cancel(mL^-1))=3.4*mol*L^-1