What should I consider when choosing an indicator for an acid-base titration? (2024)

FAQs

What should I consider when choosing an indicator for an acid-base titration? ›

Because a noticeable pH change occurs near the equivalence point of acid-base titrations, an indicator can be used to signal the end of a titration. When selecting an indicator for acid-base titrations, choose an indicator whose pH range falls within the pH change of the reaction.

The two common indicators used in acid-base titration is Phenolphthalein and methyl orange. In the four types of acid-base titrations, the base is being added to the acid in each case.

In all cases, though, a good indicator must have the following properties: The color change must be easily detected. The color change must be rapid. The indicator molecule must not react with the substance being titrated.

The most common indicator is found on "litmus" paper. It is red below pH 4.5 and blue above pH 8.2. Other commercial pH papers are able to give colors for every main pH unit. Universal Indicator, which is a solution of a mixture of indicators is able to also provide a full range of colors for the pH scale.

1 Answer. Titrations reactions mixture must be (i) rapid; (ii) quantifiable by means of an easily observed end-point; (iii) have known and definite stoichiometry.

Thymol blue, phenol red, and methyl orange are all common acid-base indicators. Red cabbage can also be used as an acid-base indicator. A particular type of acid-base indicator is a universal indicator, which is a mixture of multiple indicators that gradually changes color over a wide pH range.

Common Acid-Base Indicators

Tried-and-true indicators include thymol blue, tropeolin OO, methyl yellow, methyl orange, bromphenol blue, bromcresol green, methyl red, bromthymol blue, phenol red, neutral red, phenolphthalein, thymolphthalein, alizarin yellow, tropeolin O, nitramine, and trinitrobenzoic acid.

Litmus indicator solution turns red in acidic solutions and blue in alkaline solutions. It turns purple in neutral solutions. Litmus paper. Red litmus turns blue in alkalis, while blue litmus turns red in acids. is usually more reliable, and comes as red litmus paper and blue litmus paper.

The three most common indicators to test for acids and bases are: Litmus. Methyl orange. Phenolphthalein.

Sodium hydroxide is the strongest base as it completely dissociates to give sodium ions and hydroxide ions. These hydroxide ions reacts with hydrogen ions from the acid and completely ionises the hydrogen ions.

What are the two types of acid-base indicators? ›

Commonly used acid-base indicators- Litmus, phenolphthalein.

An appropriate acid-base indicator will change colour at the equivalence point of the titration. An appropriate indicator for an acid-base titration will change colour over a narrow pH range, and have distinctive colour at lower pH and a different, distinctive colour at higher pH.

2)Their should not be any leakage from the burette during titration. 3)Keep your eye in level with the liquid surface while taking the burette reading or while reading the pipette or measuring flask etc. 4)Always read lower meniscus in case of colourless solution and upper meniscus in case of coloured solutions.

The relative strength of an acid can be predicted based on its chemical structure. In general, an acid is stronger when the H–A bond is more polar. Acidity is also greater when the H–A bond is weaker and when the conjugate base, A⁻, is more stable.

i) The reaction between the titrant and titrate must be expressed. ii) The reaction should be practically instantaneous. iii) There must be a marked change in some physical or chemical property of the solution at the end point. iv) An indicator should be available which should sharply define the end point.

Methyl orange is the best indicator of strong acid and weak titration. Phenolphatelin indicator is good for a strong base and weak acid titration. For the strong acid and strong base titration used either Methyl orange or Phenolphatelin.

The two most common indicators used in acid-base titration are phenolphthalein and methyl orange. Phenolphthalein can be used for strong acid-strong base titrations as well as weak acid-strong base titrations. Methyl orange can be used for strong acid-weak base titration.