Question

1.) *buret is at 50 mL and you can release how much comes out into the flask. *can't copy image sorry

The flask shown here contains 10.0 mL of HCl and a few drops of phenolphthalein indicator. The buret contains 0.200 M NaOH.

What volume of NaOH is needed to reach the end point of the titration? _____mL NaOH

What was the initial concentration of HCL? ____M HCl

2.) By titration it is found that 29.5 mL of 0.140 M NaOH(aq0 is needed to neutralize 25.0 mL of HCl(aq). ______M.

Answer 1

SOLN 1

number of initial moles of NaOH = Molarity * volume

Molarity of NaOH = 0.2 V = 50 ml hence moles = 0.2 * 50 = 10 mmols

Volume of HCl = 10 ml lets say its Molarity is M therefore initial moles of NaOH = 10 * M mmols

at end point both acid and base neutralize each other hence no of moles at end point wil be equal

therefore 10 mmols of HCl molarity should be 1M (HCl)

volume of NaOH required is 50 mL

2. by the same concept above

no. of moles of NaOH (M * V) = moles of HCl (M*V)

29.5 mL * 0.14 = M * 25

M(HCl) = 29.5 mL * 0.14 / 25 mL = 0.16 M

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