molar concentration is the number of moles of solute dissolved in 1 L of solution
the mass of HF dissolved - 17.0 g
molar mass of HF - 20 g/mol
number of moles of HF = mass dissolved / molar mass
number of moles of HF = 17.0 g / 20 g/mol = 0.85 mol
volume of solution is 200 mL
number of HF moles in 200 mL = 0.85 mol
therefore number of HF moles in 1000 mL is - 0.85 mol/200 x 1000 = 4.25 mol/L
molar concentration of HF solution is 4.25 M
