Question

1.) An aqueous NaOH solution was perpared by mixing 65mL of a stock 2.8M NaOH solution with enough water to make 750mL solution. Calculate the concentration of his new NaOH solution.

2.) Consider the following reaction:

HKC₈H4O_{4 (aq)} + NaOH _(aq)---> NaKC₈H₄O_4(aq) + H₂O _(l)

If 23.45mL of NaOH solution is reqiuried to neutralize (to react completely with) 0.45g of HKC₈H₄O₄, what must be the concentration of the NaOH solution?

Answer 1

1.)

M1 = 2.8 M , V1 = 65 mL

M2 = ? , V2 = 750 mL

M1 V1 = M2 V2

2.8 x 65 = M2 x 750

M2 = 0.243 M

new solution concnetration = 0.24 M

2)

molar mass of HKC₈H₄O₄ = 204.2 g/mol

moles of HKC₈H₄O₄ = 0.45 / 204.2

                                  = 2.2 x 10^-3

from balanced equation :

mole of HKC₈H₄O₄ = mole of NaOH

2.2 x 10^-3    = moles of NaOH

volume = 23.45 mL = 23.45 x 10^-3 L

molarity = moles / volume

molarity = 2.2 x 10^-3 / 23.45 x 10^-3 = 0.094 M

molarity (concentration of the NaOH ) = 0.094 M