76 Questions . Why doesn\'t washing the sides of the flask with water during the

Question

76 Questions . Why doesn't washing the sides of the flask with water during the titration cause an error in the calculation? Explain the effect (too high, too low, or no effect) on the calculated molarity (compared to the actual molarity) of your standard NaOH solution, if: 2. Some of the oxalic acid solution splashes out of the flask before the end point is reached. a. b. The solution in the Erlenmeyer turns a persistent dark pink during titration. c. The 6 M stock solution of NaOH is really 5.5 M.

Explanation / Answer

1) In order to understand an effect, let us consider a direct titration.

Usually we use a volumetric pipette to pass the acid solution to the erlenmeyer used on the titration, so the volume of acid is known.

Adding distilled water to this erlenmeyer will change its volume, but will not change the number of mols of acid present within, neither the initial volume we have added of the acid solution. In some cases, it is advisable to some water so that it becomes easy for us to make the color change more visible.

Our aim of titration is to find the volume of the base (of known concentration) necessary to neutralize the acid. As we know the volume of acid added in the erlenmeyer (the pipette volume), calculate the concentration of the acid solution.

Water in the buret can cause variations in the concentration of the base being used therefore we rinse it with the base, so we have a good precision titration. On the contraray, the erlenmeyer can be rinsed only with distilled water, since the volume of acid solution used for the calculation is constant.

We will have a equation as given below:

Vbase*Cbase = Vacid*Cacid*f

Where, Vbase is the volume of base consumed in the titration,

Cbase is the concentration of the base (which is known),

Vacid is the volume of the solution of acid added to the erlenmeyer (the volume of the pipette),

Cacid is the estimated concentration of the acid and

f is the correction coefficient (so the real acid concentration is Cacid*f).

2 a) If some acid is spilled out of the flask after it is weighed, the calculated equivalent mass of the acid will be too high.

This is because the equivalent mass is calculated using the mass of the acid and if some acid is lost after it is weighed then there will be less acid in the reaction, so the calculated equivalent mass will be higher than the actual equivalent mass that reacts.

Related Questions

Navigate

• Browse (All)
• Browse 7
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.