Red Cabbage Indicator: Overview, Questions, Preparation

Updated on Jun 4, 2024 17:06 IST

An acid is a material that donates protons or accepts a pair of valence electrons to form a bond. A base is a compound that can accept protons or donate a pair of electrons to form a bond. Bases may be thought of as the molecular opposite of acids.

Table of content

Indicators
Red Cabbage Indicator pH Colours
Illustrated Examples
FAQs on Red Cabbage Indicator

Indicators

As the concentration of hydrogen (H+) or hydroxide (OH-) ions varies in an aqueous solution, an acid-base signal becomes either a weak acid or a weak base that indicates a colour transition. Indicators are substances which, when brought into contact with acids and bases, demonstrate a change in colour. To identify the endpoint of an acid-base reaction, acid-base markers are most commonly used in the titration. They are also used for calculating pH values and for fascinating demonstrations of colour-change physics.

The red cabbage indicator is used to test if the solution is an acid or a base. The cabbage contains a pigment molecule called flavin or anthocyanin that changes colour depending on the solution’s acidity.

Usually, when mixed with an acid, the purple-coloured solution turns red, and when combined with a base, it turns green. It is mainly neutral if the material doesn’t allow the colour to change.

Red Cabbage Indicator pH Colours

pH	Colours
2	Red
4	Purple
6	Violet
8	Blue
10	Blue-green
12	Greenish yellow

Red Cabbage Indicator in Class 10

The basics of acids and bases, along with different indicators, are well-explained in the class 10 textbooks. The chapter also explains other natural and synthetic indicators that are available and explains the entire process of doing the experiments by using natural and synthetic indicators. The chapter also explains the process of neutralisation and how we are using neutralisation in our daily life.

The uses of acids and bases are outlined in almost every chapter of the class 10 textbook. The use of many other indicators has also been explained in a later chapter.

Illustrated Examples

1. Red Cabbage Indicator changes to which colour with a strongly alkaline solution?

Answer: Green

2. When added to a base or alkali (such as sodium hydroxide), what colour does the red cabbage extract change?

Answer: In basic solutions, red cabbage extract turns greenish-yellow.

FAQs on Red Cabbage Indicator

Q: Why is red cabbage a good indicator?

A: Red cabbage produces a dye called anthocyanin that is water-soluble and changes colour when combined with an acid or a base. It is considered a good indicator because it tells us something about other compounds’ chemical structure.

Q: How does the predictor work for red cabbage?

A: Red cabbage juice carries a natural pH indicator that shifts colours based on the solution’s acidity. Acidic solutions turn a red colour on the indicator, neutral solutions turn a purple colour, and simple solutions turn a greenish-yellow colour.

Q: Why is red cabbage not a good buffer indicator?

A: The indicator standards will only give you pH values of 2, 4, 6, 7, 8, 10, and 12, with no values in between. This makes the identification of minor pH shifts difficult.

Q: Is the red cabbage indicator more useful than litmus-like indicators?

A: Yes, the indicator for red cabbage will be more helpful because it not only demonstrates whether a solution is acidic or basic but also provides a hint of how acidic the solution is or how basic it is.

Q: In an acid solution, what is the colour of red cabbage?

A: Red cabbages, for example, possess an indicator pigment molecule called flavin, which is a type of anthocyanin molecule. An anthocyanin will turn very acidic solutions red, while neutral solutions will make it purple and fundamental solutions will turn greenish-yellow.