Why is the colour of KMnO4 purple before the titration and after the end point it is pink?
The colour is still the same. Rather, dilution plays a factor here. When you perform a redox titration with permanganate, the titrant (KMnO[math]_4[/math]) in the burette is deep purple in colour. This is because the concentration is quite large. When you start the titration, the dark purple KMnO[math]_4[/math] is slowly added into the sample you are titrating. Under some heat and acidic conditions, this will cause the Mn which is in 7+ oxidation state in the permanganate to reduce into 2+ state as it reacts with the sample. The 2+ state is colourless, so no net change is observed as long as there is still some sample left.Now, once the sample has fully reacted with the KMnO[math]_4[/math] at the end point, the additional KMnO[math]_4[/math] will now remain in the 7+ state. The concentration of this extra Mn[math]^{7+}[/math] is quite small, so it imparts a pink tinge instead of the stronger purple.
Why do we use an indicator in titration?
We use a indicator in titration so that we can know when the reaction is completed as mostly both the acid and bases are white so you cant tell without a indicator when the reaction between acid and base have finished,you can see that the reaction end in titration when the colour changes different indicators have different colour likePhenolphthalein changes from purple to pinkmethyl orange changes from yellow to orange….Hope this helps.
What is the role of phenolphthalein indicator in titration of hydrochloric acid and sodium hydroixde?
It is an indicator which changes from clear to pink at basic pH, which is pH 8.2 for phenolphthalein. But since the solution is not buffered in a titration, it is a good signal when neutrality has been reached. So when you add base to an acid solution, as soon as the pink color no longer fades, all the acid is neutralized. From the amount of base added, you can determine the concentration of the acid.
How do you find the concentration of oxalic acid when titration against potassium permanganate?
The reaction involved in this titration is:2MnO4− + 5H2C2O4 + 6H+⟶ 2Mn2+ + 10CO2 + 8H2OSo, this defines the stoichiometry of the reaction and for every 2 equivalents of permanganate (MnO4−), 5 oxalic acids (H2C2O4) are consumed. Also note that the color of solutions of permanganate are intensely purple colored while manganese (Mn2+) solutions are a very light pink color.So, you will need to know the concentration of your permanganate solution (lets say it is 0.001 M). With this solution, titrate the oxalic acid solution until the purple color disappears (a little tricky since manganese solutions are lightly pink). Note what this volume is and multiple the concentration. Lets say the titration took 25 mL (or 0.025 L) of you 0.001 M solution and remember that the ratio of oxalic acid to permanganate is 5/2. The amount of oxalic acid then is:Oxalic acid (Moles) = vol of permanganate solution * concentration of permanganate * ratio of oxalic acid/permanganate orOxalic acid (Moles) = 0.025 L * 0.001 moles/L * 5/2 = 0.0000625 moles.If you wanted a concentration then you would need to know the volume of the oxalic acid solution. Lets say it was also 25 mL (0.025 L) then the concentration of the oxalic acid would be:[Oxalic Acid] = (0.0000625 moles)/(0.025 L) = 0.0025 m/L (or M)
Why does the addition of water to a conical flask during a titration have no effect on the results?
Titration is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of a known reactant. Because volume measurements play a key role in titration, it is also known as volumetric analysis. The reaction between two chemical substances in this experiment are NaOH and HCl is : NaOH + HCl --> NaCl + H2O or in ionic OH- + H+ --> H2O so in this experiment the titrant (known reactant), HCl, is use to determine the volume needed to neutralized NaOH. Because H+ = OH- so we can use mole concept to determine the concentration of unknown substance, NaOH. By using the equation below V1(ml, NaOH) x M1(M, NaOH) = V2(ml, HCl) x M2 (M, HCl) so we can find and determine the concentration of NaOH because the volume of NaOH and HCl also concentration of HCl as the titrant. So by adding water to the conical flask won't effect the results, because when we doing titration the most important thing is the volume of the known reagent and also water in this experiment doesn't react with other chemical components in the reaction.