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What is a Universal Indicator?

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Universal Indicators in Chemistry is defined as a chemical indicator that is used to check the pH for a wide range of solutions. In general, when we use any chemical indicator it is used to identify the acid or base but does not cover the range of acid and base it also does not cover the strength of the acid and base. In that case, we use a universal indicator as it also tells the acidic or basic strength of the solution.

Here in this article, we will learn about Universal Indicators, universal indicator colour charts, universal indicator examples and others in detail.

What is the Universal Indicator?

Universal Indicator is a pH indicator that is formed by mixing various pH indicators in a fixed proportion and it exhibits a smooth colour change when the pH of the solution changes from 0 to 14. The universal indicator also tells us about the strength of the solution apart from the nature of the solution.

Litmus is a common chemical indicator used for determining if a chemical is an acid or a base. But it i unable to determine whether a chemical is a strong acid, a weak acid, a strong base, or a weak base. Litmus, for example, can determine that sulphuric acid and vinegar are both acidic, but it cannot determine whether sulphuric acid is a stronger acid or more acidic than the vinegar solution.

To overcome this challenge we use Universal indicators that works by detecting the pH of a solution, to determine the strength of an acid or basic solution.

Universal Indicator Definition

A universal indicator is a mixture of several different indicators or dyes that produce varied colours at various pH levels across the pH scale. A universal indicator is formed as a mixture of Water, Propanol, Phenolphthalein Sodium Salt, Sodium Hydroxide, Methyl Red, Bromothymol Blue Monosodium Salt, and Thymol Blue Monosodium Salt.

Universal Indicator Color Chart

Universal indicator shows different colours at different concentrations of hydrogen ions or the pH of a solution. The universal indicator takes on a new colour when an acid or basic solution is put into it. By comparing the colour of the universal indicator to the colours on the pH colour chart, the pH value of the acid or base solution can be determined. We can tell whether a solution is a strong acid, weak acid, stronger base, or weak base by looking at the pH value color chart. The colours that the universal indicator produces at various pH levels are shown in the table added below.

pH Range

Colour of Universal Indicator

Acid/Base Description

<3

Red

Stronly Acidic

3 – 4

Orange

Acidic

5

Yellowish – Orange

Weak Acid

6

Yellow

Slightly Acidic

7

Green

Neutral

8

Blue – Green

Slightly Alkaline

9

Blue

Weak Alkali

> 10

Voilet

Strong Alkaline

Universal indicator manufacturers give a pH colour chart that is used to gives the strength of the acidic or basic solution. The universal colour chart is added in the image below,

Universal-Indicator

pH for Acids

pH of acids or acidic solutions is less than 7. A solution with a pH of less than 7 is said to be acidic. For example, a pH of 4 indicates that the solution is acidic. It should be remembered that the lower the pH of a solution, the more acidic it is. A pH 1 solution, for example, is substantially more acidic than a pH 4 solution. To put it in another way, a pH 1 solution is a significantly stronger acid than a pH 4 solution. Strong acids are often defined as solutions with a pH of 0, 1, 2 or 3. Weak acid solutions have a pH of 4, 5, or 6. It is obvious that a substance’s acidity is proportional to its pH. The pH of strongly acidic chemicals is quite low. In fact, the stronger the acid, the lower the pH.

Since all solutions with a pH less than 7 are acidic in nature, they turn blue litmus red. In addition, they cause the methyl orange indicator to turn red.

pH for Bases

pH of bases or basic solutions is greater than 7. When a solution has a pH greater than 7, it is referred to as the basic solution. A solution with a pH of 12 will, for example, be basic in nature or a base. It should be remembered that the higher the pH of a solution, the more basic it is. A solution with pH 14, for example, is significantly more basic than a solution with pH 11.  In other words, a pH 14 solution will be a much stronger base than an acid with a pH of 11. Strong bases are often defined as solutions with a pH of 11, 12, 13, or 14. Weak bases are defined as solutions with pH values of 8, 9, and 10. The pH of very basic compounds is extremely high. In fact, the stronger the base, the higher the pH.

Since all solutions with a pH greater than 7 are basic in nature, they turn red litmus blue. In addition, they make the phenolphthalein indicator pink.

pH for Neutral Substances

pH of neutral substances is exactly 7. Pure water is neither acidic nor basic; it is a neutral substance. As a result, pure water has a pH of 7. A sugar solution and a chloride solution are both neutral, with a pH of 7. As a result, any solution with a pH of 7 is considered neutral. Litmus paper, as well as other common indicators like methyl orange and phenolphthalein, will have no impact on a material with a pH of 7.

How is Universal Indicator Used?

On a strip of universal indicator paper, a drop of the solution to be tested is put. The colour of the indicator paper will change where the solution has been applied. The colour on the indicator paper is then compared to a colour on the standard pH colour chart. The pH value corresponding to this colour may be found on the pH colour chart. We can tell whether a solution is a strong acid, a weak acid, a strong base, or a weak base based on its pH value.

If a drop of a solution is placed on universal indicator paper and the paper turns dark red, the pH of the solution is near zero, indicating that it is a strong acid. However, if an orange colour is generated, the pH will be about 4 and the acid will be weak. Different colours can also be created using a different base solution. Weakly basic solutions are blue, whereas extremely basic solutions are violet with a universal indicator. If a solution turns the universal indicator green, it is a neutral solution that is neither acidic nor basic. As a result, water will take on a green colour when tested with a universal indicator.

Types of Universal Indicators

On the basis of the applications universal indicators are categorized into two types,

  • Universal Indicator Solution
  • Universal Indicator Paper

Universal Indicator Solution

Universal Indicator in the liquid form is called universal indicator solution that is a mixture of various solutions and dyes. This universal indicator solution is directly added to the solution whose pH is to be found and the change in colour of the solution tells the nature and the strength of the solution.

Universal Indicator Paper

Universal Indicator Paper is a special paper that is dyed with the universal indicator solution and the paper so formed is called the universal indicator paper and dipping this paper in the given solution we test the nature and the strength of the solution.

Universal Indicator Examples

Universal Indicators are of two types for example,

  • Natural Universal Indicators
  • Artificial Universal Indicators

Natural Universal Indicators

Natural Universal Indiacator as the name suggest are the universal indicators that are obtained from natural sources. Some examples of the natural universal indicators are,

  • Red Cabbage
  • Blueberries
  • Turmeric
  • Beetroot
  • Chinarose, etc.

Artificial Universal Indicators

Artficial Universal Indiacator as the name suggest are the universal indicators that are made artificially. Some examples of the artifical universal indicators are,

  • Bromothymol Blue
  • Phenolphtalein
  • Methyl Oragne, etc.

Read More,

Universal Indicator: FAQs

1. What is a Universal Indicator Class 10?

A universal indicator is a chemical indicator that works for a wide range of acid and base solution. This indicator also tells us the strength of the acid and base solution by changing its colour accordingly.

2. What is the Most Common Universal Indicator?

pH Scale is the most common universal indicator used to identify acid and bases.

3. Why is it Called a Universal Indicator?

Univeral Indicators are called the Universal because they are used for a wide variety or the range of the solution and only one indicator can tell us the nature and strength of the wide range of solution.

4. What is Universal Indicator and pH Indicators?

A universal indicator is a mixture of various pH indicators and it gives a solution that is used to tells the nature and strength of the acidic and basic solution.

5. What will the solution of pH be when blue litmus is changed to red?

A solution that changes the colour of blue litmus to red is acidic. Acidic solutions are those that have a pH of less than 7. As a result, the solution’s pH will be less than 7.

6. What is the pH of Curd?

When milk turns into curd, it becomes acidic, and its pH drops below 6.

7. What is the pH of Milk?

Mlik is slightly acidic and the pH of the milk is 6.

8. What is Difference Between Universal Indicator and Litimus Paper?

Litimus paper and UniversalmIndicator both are the chemical substance that are used to determine the nature of the solution.

The basic difference between Litimus Paper and Universal Indicator is that litmus paper is used for a specific solution, but universal indicator is used for a wide range of the acidic and basic solution. Universal indicator also gives the strength of the acidic and basic solution.



Last Updated : 02 Nov, 2023
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