Quick Answer: Is Phenolphthalein An Acid Or Base?


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).

Is phenolphthalein basic or acidic?

Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and red in basic solutions. It belongs to the class of dyes known as phthalein dyes.

What is the pH of phenolphthalein?

Phenolphthalein and the pH Scale

Phenolphthalein works somewhat differently as it is naturally colorless but turns pink in alkaline solutions. The compounds 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 purple in stronger alkalines.

Is phenolphthalein a strong base?

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.

Does phenolphthalein affect pH?

How does phenolphthalein affect the pH of the base during a titration? A few drops cannot change the pH at all. The reverse is much more significant: phenolphthalein is affected by the basic environment, changing into its basic form, giving a pink colour.

Is NaOH an acid or base?

NaOH, or sodium hydroxide, is a compound. A compound is classified as either an acid, base, or salt. All bases contain OH- (hydroxide) ions, while all acids contain H+ (hydrogen) ions. A salt is a compound that is formed when a base and an acid are combined because they neutralize each other.

Why is methyl orange orange in Colour?

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.

What is an acid in chemistry?

Acid Definition in Chemistry

An acid is a chemical species that donates protons or hydrogen ions and/or accepts electrons. Most acids contain a hydrogen atom bonded that can release (dissociate) to yield a cation and anion in water.

What is indicator in titration?

Indicator: A substance that changes color in response to a chemical change. An acid–base indicator (e.g., phenolphthalein) changes color depending on the pH. Redox indicators are also used. A drop of indicator solution is added to the titration at the beginning; the endpoint has been reached when the color changes.

What is the pH of methyl orange?

At pH values less than 3.1, methyl orange is red and a pH values greater than 4.4, it will be yellow. In the range between 3.1 and Indicators are weak acids or bases which change color depending on the pH of the solution.

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. Weak acids, like strong acids, ionize to yield the H+ ion and a conjugate base. Because HCl is a strong acid, its conjugate base (Cl−) is extremely weak.

Is NaOH a strong base?

Sodium hydroxide (NaOH) is strong base because it fully dissociates in water to produce hydroxide ions. While weak bases produce fewer hydroxide ions, making the solution less basic.

Is koh a strong base?

KOH is potassium hydroxide. Since it is composed of the hydroxide anion (OH-), it is a strong base. The two ions (K+ and OH-) completely ionize in water. So KOH is both a strong base and a salt.

What is the pH range of phenolphthalein?

Indicator Range

IndicatorColourpH range
Bromothymol Blueyellow6.0 – 7.6
Phenol Redyellow6.8 – 8.4
Thymol Blue – 2nd changeyellow8.0 – 9.6
Phenolphthaleincolourless8.2 – 10.0

14 more rows

How much phenolphthalein is in titration?

The reason they say “two drops” and not “at least two drops” is that they don’t want you to be wasteful. Phenolphtalein is slightly acidic. It does affect titration because if you add too much, then it will alter the concentration of whichever solution you are adding it in.

Why phenolphthalein is Colourless in acid?

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 NaOH strong acid?

Solution: NaOH is a strong base but H2C2O4 is a weak acid since it is not in the table. Therefore, this is a weak acid-strong base reaction which is explained under the link, titration of a weak acid with a strong base.

Is c2h5nh2 a weak base?

A buffer solution is an aqueous solution that contains a weak acid and its conjugate base and weak base and its conjugate acid. Ethylamine (C2H5NH2) is a weak base with pKb = 3.3 and its conjugate acid is the protonated version which is the C2H5NH3+.

Is NaOH a weak acid?

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.

Is methyl orange basic or acidic?

Methyl Orange is the red, weak acid which dissociates in water forming orange neutral molecules. Under acidic conditions, the equilibrium is to the left, and the concentration of the neutral molecules is too low for the orange colour to be observed.

Do bases turn pink?

Phenolphthalein is an indicator of acids (colorless) and bases (pink). Sodium hydroxide is a base, and it was in the pitcher at the beginning, so when added to the phenolphthalein in beakers 2 and 4, it turned pink (top half of the graphic). The equilibrium shifts right, HIn decreases, and In- increases.

Is methyl orange is a natural indicator?

Turmeric,red cabbage, flowers of hydrangea etc are natural indicators. Methyl orange and phenolphthalein are synthetic indicators and are prepared in laboratory.