2. Dilution and Standardization of NaOH solution Obtain a beaker filled with dis

Question

2. Dilution and Standardization of NaOH solution Obtain a beaker filled with distilled water. Fill the 500mL volumetric flask with distilled water to about one third of the way. Using a graduated cylinder, measure 50mL of the unknown NaOH solution and slowly add the base to the volumetric flask. (BE VERY CAREFUL WITH THE NaOH - DO NOT SPLASH THE SOLUTION, IT WILL BURN IF IT COMES INTO CONTACT WITH YOU) Mix the solution using a swirling motion. Finally add the remainder of distilled water to the mark and mix thoroughly. Transfer this solution to a clean beaker for storage. Weigh approximately 1 g of KHP and add it to an Erlenmeyer flask with approximately 50 mL of distilled water. If KHP is difficult to dissolve, heat the solution on a hot plate. Then, add 2-3 drops of phenolphthalein indicator to the flask. Begin titrating the KHP solution with the diluted NaOH solution. Repeat this titration 1 more time for a total of 2 trials.

Explanation / Answer

Answer – We are given the data for the two trials , so the

Average volume used for the NaOH = 46.4 +46.0 / 2

                                                         = 46.2 mL

The average mass of KHP = 1.0140 g + 0.9985 g / 2

                                           = 1.00625 g

Now we need to calculate the moles of KHP

Mole sof KHP = 1.00625 g / 204.22 g.mol-1

                        = 0.00493 moles

We know the reaction –

KHP + NaOH -----> NaKP + H2O

So, from the above balanced reaction –

1 moles of KHP = 1 moles of NaOH

So, moles of NaOH = 0.00493moles

We know, molarity of NaOH = moles / L

                                           = 0.00493 moles / 0.0462 L

                                            = 0.107 M

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