Pre-Lab Questions 1. A KHP sample that weighs 2.56 grams requires 31.55 mL of Na

Question

Pre-Lab Questions 1. A KHP sample that weighs 2.56 grams requires 31.55 mL of NaOH solution to be completely titrated. Determine the concentration of the NaOH solution. a. Determine the number of moles of KHP. b. Determine the number of moles of NaOH required to neutralize KHP c. Determine the concentration of the NaOH solution. 2. Define equivalence point. 3. You will use an acid-base indicator today to carry out the titration of KHP with an NaOH solution a. What is the name of the acid-base indicator? b. Why do you need to use the acid-base indicator? c. What will be the color of the acid-base indicator if the ph is basic? d. What will be the color of the acid-base indicator if the pH is acidic? 149

Explanation / Answer

PRE - LAB

1.

When KHP reacts with NaOH then H from carboxylic acid group is replaced by Na of NaoH and corresponding salt and water is formed . for this the reaction can be written as:

KHP(C8H5KO4) + NaOH ----------> C8H4KO4Na + H2O

A) Now moles of KHP = given mass/molar mass of KHP

Moles = 2.56 g/204.22 g mol^-1 = 0.01254 mol

b) From chemical reaction it is clear that

Moles of KHP = moles of NaOH reacted = 0.01254 mol

C) concentration of NaOH = moles/volume of solution in L

Volume = 31.55 ml = 0.03155 L

Concentration = 0.01254 mol / 0.03155 L = 0.3975 mol/L

= 0.3975 M

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