Why is phenolphthalein used in titration instead of methyl orange?

Asked By: Anabella Hinnemann | Last Updated: 31st May, 2020
Category: science chemistry
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Phenolphthalein changes colour at a pH above 7. So it is quite good as an indicator for titrations of strong acids with strong bases. It is also suitable for titrations of weak acids and strong bases, which have an equivalence point at a pH above 7. Methyl orange changes colour at a suitable pH.

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Likewise, people ask, why is methyl orange used in titration?

Methyl orange is a pH indicator frequently used in titration because of its clear and distinct color variance at different pH values. Methyl orange shows red color in acidic medium and yellow color in basic medium. Because it changes color at the pH of a mid strength acid, it is usually used in titration for acids.

One may also ask, what indicator can be used instead of phenolphthalein? This will be explored further down this page. Phenolphthalein is another commonly used indicator for titrations, and is another weak acid. In this case, the weak acid is colourless and its ion is bright pink.

indicator pKind
litmus 6.5
methyl orange 3.7
phenolphthalein 9.3

Also asked, why is phenolphthalein used in titration?

A strong acid- strong base titration is performed using a phenolphthalein indicator. Phenolphtalein is chosen because it changes color in a pH range between 8.3 – 10. It will appear pink in basic solutions and clear in acidic solutions. Titration: Titration of an acid-base system using phenolphthalein as an indicator.

What is the Colour change of phenolphthalein?

Phenolphthalein is naturally colorless but turns pink in alkaline solutions. The compound remains colorless throughout the range of acidic pH levels but begins to turn pink at a pH level of 8.2 and continues to a bright magenta at pH 10 and above.

39 Related Question Answers Found

Is methyl orange an acid or base?

Answer and Explanation: Methyl orange is an acid-base indicator. The solution used for titrations typically is a 0.1% aqueous solution.

What happens when methyl orange is added to NaOH?

what happens when methyl orange is added to NaOH ? When methy orange is added to a solution of NaOH then it will impart a yellow colour. Methy orange generally changes from yellow to red in acidic medium.

Is methyl orange a natural indicator?

A natural indicator is obtained from natural sources while synthetic indicators are man made and do not occur in nature. Turmeric,red cabbage, flowers of hydrangea etc are natural indicators. Methyl orange and phenolphthalein are synthetic indicators and are prepared in laboratory.

Which indicator is best for titration?

The pH range of phenolphthalein is about 8.3 to 10.0, but the titration curve is so steep at the equivalence point that phenolphthalein makes a good indicator. For a strong base-weak acid titration, the equivalence point is probably near pH 9. Phenolphthalein is great for this titration.

Is HCl a strong acid?

A strong acid is an acid which is completely ionized in an aqueous solution. Hydrogen chloride (HCl) ionizes completely into hydrogen ions and chloride ions in water. Because HCl is a strong acid, its conjugate base (Cl) is extremely weak.

Why is universal indicator not used in titration?

Litmus is not used in titrations because the pH range over which it changes colour is too great. Universal indicator which is actually a mixture of several indicators displays a variety of colours over a wide pH range so it can be used to determine an approximate pH of a solution but is not used for titrations.

What is double indicator titration?

A double indicator titration is the process used in chemistry experiments to determine and analyze the amount and concentration of acids or bases in a solution at two end points.

Why is methyl orange not a good indicator?

Methyl orange is an indicator with a pH range of 3.1-4.4. It is not a suitable indicator for the neutralization reaction between the weak acid oxalic acid ( H2C2O4 H 2 C 2 O 4 ), and strong base sodium hydroxide ( NaOH N a O H ) because its pH range does not include the equivalence point pH (~8) for the reaction.

Is NaOH an acid or base?

NaOH is a base because when dissolved in water it dissociates into Na+ and OH- ions. It is the OH- (hydroxyl ion) which makes NaOH a base. In classical term a base is defined as a compound which reacts with an acid to form salt and water as depicted by the following equation.

What is the pH of phenolphthalein?

As an indicator of a solution's pH, phenolphthalein is colourless below pH 8.5 and attains a pink to deep red hue above pH 9.0.

Why is standardization of NaOH important?

First of all, solid NaOH absorbs water from the air, so accurately weighing a sample during the preparation of a solution is impossible. Once the NaOH solution has been standardized and its concentration is well-known, it can be used to titrate other acid solutions such as HCl.

What is end point in titration?

End Point. end point: the point during a titration when an indicator shows that the amount of reactant necessary for a complete reaction has been added to a solution.

What is the Colour of phenolphthalein in neutral solution?

It is colourless in a neural (and acidic) solution. It starts to turn pink in an alkaline solution (8.2 or greater) and darkens to purple the stronger the base. Phenolphthalein is colorless at pH 7.0.

What is the pH of an indicator?

pH indicators are weak acids that exist as natural dyes and indicate the concentration of H+ (H3O+) ions in a solution via color change. A pH value is determined from the negative logarithm of this concentration and is used to indicate the acidic, basic, or neutral character of the substance you are testing.

Why does phenolphthalein turn pink then clear?

Phenolphthalein (HIn) is weakly acidic in nature. And in aqueous solution, it dissociates into and ions. The pink colour of the solution is due to the concentration of ions in the solution. Under acidic conditions, the concentration of in the solution is very low and concentration of is high, hence it is colourless.

Is phenolphthalein an acid or base?

Phenolphthalein. Phenolphthalein is an organic compound (C20H14O4) used as an acid-base indicator. The compound is colorless in acidic solution and pinkish in basic solution (with the transition occuring around pH 9).

Why is phenolphthalein dangerous?

May cause irritation of the digestive tract. Ingestion may cause fever, blood pressure increase and other unspecified vascular effects. Inhalation: May cause respiratory tract irritation. May be harmful if inhaled.