Posted: May 30th, 2015

procedure Chemistry lab

procedure Chemistry lab

Rinse and fill a 50 mL buret with standard 0.100 M sodium hydroxide (NaOH) solution. Pipet
25.00 mL of the “unknown” hydrochloric (HCl) solution into a 250 mL beaker containing a stir
bar. Add about 50 mL of deionized water to the beaker. (The additional water is required to
provide a solution volume sufficient to cover the pH electrode bulb in a subsequent titration. It
is added here to ensure all titrations are carried out in the same manner.) Add 3 drops of
phenolphthalein indicator. Gently stir the solution in the beaker using the magnetic stirrer.

Read and record the initial buret reading to 2 decimal places. To prevent splashing, ensure the
tip of the buret is below the top of the beaker. Slowly add NaOH from the buret. When a
localized pink colour appears, slow the addition of NaOH to one drop at a time. The endpoint is
a pale pink colour. When the solution turns pale pink (or dark pink if you overshoot)
immediately stop the addition of NaOH. Allow the solution to settle in the buret for at least 30
seconds. Read and record the final buret reading. Also record the colour of your solution (light
pink, medium pink, dark pink, etc).