Question

You wish to make a 0.398 M hydroiodic acid solution from a stock solution of 3.00 M hydroiodic acid. How much concentrated acid must you add to obtain a total volume of 100 mL of the dilute solution?

Answer 1

$C_m= \frac{\nu}{V}$

C_m - molarity or molar concentration of the solution

$\nu$ - amount of the solute

V - volume of the solution

$\nu(HI)=const=C_{m1} \cdot V_1=C_{m2} \cdot V_2$

C_m1 - initial molarity of the solution

V₁ - initial volume of the solution

C_m2 - final molarity of the solution

V₂ - final volume of the solution

$V_1=\frac{C_{m2} \cdot V_2}{C_{m1}}$

$V_1=\frac{0.398 \; M \cdot 100.0 \; mL}{3.00 \; M} \approx 13.27 \; mL$

Answer: 13.27 mL.