Table of Contents
- 1 Why phenolphthalein is not suitable indicator for titrating a weak base against strong acid?
- 2 Why is chemical indicator method not suitable for titration between weak acid and weak base?
- 3 Why phenolphthalein is used in titration experiment?
- 4 Why is phenolphthalein used as an indicator instead of methyl orange?
- 5 Can you titrate a weak acid?
- 6 Why Phenolphthalein is not used as an indicator in titration?
- 7 What is the PIN value of phenolphthalein used as an indicator?
Why phenolphthalein is not suitable indicator for titrating a weak base against strong acid?
Hence the main reason is that phenolphthalein is a weaker acid than the acid that is to be titrated. The endpoint pH (equivalent point) of a reaction between a weak acid and a strong base is given by pH = 1/2 pKw + 1/2pKa + 1/2 log [acid]. Phenolphthalein changes color in the pH range of 8.3 to 10.
Why is chemical indicator method not suitable for titration between weak acid and weak base?
If both are of equal strength, then the equivalence pH will be neutral. However, weak acids are not often titrated against weak bases because the colour change shown with the indicator is often quick, and therefore very difficult for the observer to see the change of colour.
Is best indicator used in titration of strong acid and weak base?
methyl orange
As acid is added, the solution becomes acidic and methyl orange changes color to red. So color change from yellow to red is an endpoint. In the titration of strong acid and weak base, the indicator used is Methyl Orange.
Why can’t you titrate a weak acid with a weak base?
Why phenolphthalein is used in titration experiment?
Why is phenolphthalein used in the experiment? Phenolphthalein is used as indicator for titrations for titrations. Phenolphthalein is used because it changes colour close to pH 7, the pH of the equivalence point of a strong acid with a strong base. The phenolphthalein has an easy colour change, from colourless to pink.
Why is phenolphthalein used as an indicator instead of methyl orange?
If you use phenolphthalein, you would titrate until it just becomes colourless (at pH 8.3) because that is as close as you can get to the equivalence point. On the other hand, using methyl orange, you would titrate until there is the very first trace of orange in the solution….
| indicator | pKind |
|---|---|
| phenolphthalein | 9.3 |
Is na2co3 a weak base?
Na2CO3 is a basic salt having a pH value close to 11, made from the neutralization of a strong base(NaOH) with a weak acid (H2CO3). The aqueous solution of sodium carbonate(Na2CO3) is basic in nature due to having more hydroxide ions produced from the hydrolysis of carbonate ions (CO32- + H2O → HCO3– + OH–).
When titrating a weak acid with a strong base the pH at the equivalence point will be?
> 7.00
POINT OF EMPHASIS : The equivalence point for a weak acid-strong base titration has a pH > 7.00. For a strong acid-weak base or weak acid-strong base titration, the pH will change rapidly at the very beginning and then have a gradual slope until near the equivalence point.
Can you titrate a weak acid?
The titration of a weak acid with a strong base involves the direct transfer of protons from the weak acid to the hydoxide ion. The reaction of the weak acid, acetic acid, with a strong base, NaOH, can be seen below. In the reaction the acid and base react in a one to one ratio.
Why Phenolphthalein is not used as an indicator in titration?
So Phenolphthalein can’t be used since its pH range is 8.3 to 10.0. So Methyl orange is used as the indicator in this case. In the Titration of strong acid versus strong base there is a sudden change in the pH of 3.0 to 10.0.
What is the best indicator for weak acid titration?
Indicators for Weak Acid – Strong Base Titrations. A suitable indicator for the titration of the weak acid CH 3 COOH(aq) and the strong base NaOH(aq) would be either thymol blue (pH range 8.0 – 9.6) or phenolphthalein (pH range 8.3 – 10.0).
How do you find the pH of phenolphthalein?
The endpoint pH (equivalent point) of a reaction between a weak acid and a strong base is given by pH = 1/2 pKw + 1/2pKa + 1/2 log [acid]. Phenolphthalein changes color in the pH range of 8.3 to 10.
What is the PIN value of phenolphthalein used as an indicator?
The indicator works best for pH=pIn + (+/- ) 1. The pH value at equivalence point for weak acid – strong base will be towards basic side. The pIn of phenolphthalein lies in this basic range making it suitable for said purpose. Any indicator with such pIn value can be used. How can I save money on my prescriptions?