If 100 mL of HCl gas at 300 K and 200 kPa dissolved in pure water requires 12.50 mL of the NaOH solution to neutralize in a titration experiment, what is the concentration of the NaOH solution?

1 Answer
Aug 10, 2014

The concentration of the NaOH solution is 0.641 mol/L.

There are four steps to this calculation.

  1. Write the balanced chemical equation for the reaction.
  2. Calculate the moles of HCl.
  3. Convert moles of HCl → moles of NaOH.
  4. Calculate the molarity of the NaOH.

Step 1.

HCl + NaOH → NaCl + H₂O

Step 2.

PV=nRT

n=PVRT=200kPa×0.100L8.314kPa⋅L⋅K¹mol¹×300K = 8.019 × 10⁻³ mol

Step 3.

Moles of NaOH = 8.019 × 10⁻³ mol HCl × 1mol NaOH1mol HCl = 8.019 × 10⁻³ mol NaOH

Step 4.

Molarity of NaOH = moles of NaOHlitres of solution=8.019×10³mol0.01250L = 0.641 mol/L (3 significant figures)

The molarity of the NaOH is 0.641 mol/L.