Subject: Science
An indicator is a substance which changes color in the presence of acids or alkalis. In the laboratory, we use three indicators. These are litmus, phenolphthalein, and methyl orange.
Indicator | Acid | Base |
Red litmus | No change in color | Blue in color |
Blue litmus | Red in color | No change in color |
Phenolphthalein | Colorless | Rose color |
Methyl orange | Red in color | Yellow in color |
Turmeric powder mixed with water is a bright orange-yellow which turns a brick red in the presence of alkali. Indicator can be prepared by boiling, mashing and straining a finely chopped beetroot. Many red or blue colored flowers contain natural dyes which can be used as indicators.
The pH scale is a standard scale, which is used for measuring the approximate strength of an acid or an alkali solution.
The pH scale has ranged from 1 to 14. Acidic solutions have a pH value less than 7 while alkaline solutions have a pH value greater than 7. Distilled water has pH value 7 and is called neutral substance. Strong acids have pH value 1 or 2 while strong alkali's have pH value 13 or 14.
From the pH scale, we can say that higher the hydrogen ion concentration, lower is the pH value and vice versa.
What is an indicator?
An indicator is a chemical substance which has capacity to show the termination of a chemical reaction by changing its colour.
What happens to blue litmus in an acidic medium?
Blue litmus turns into red in an acidic medium.
What happens to red litmus in a basic medium?
Red litmus turns to blue in basic medium.
What is pH scale?
The pH scale is a standard scale, which is used for measuring the approximate strength of an acid or an alkali solution. The pH scale has ranged from 1 to 14.
What is turmeric powder mixed with water?
Turmeric powder mixed with water is a bright orange-yellow which turns a brick red in the presence of alkali.
Write short note on the pH scale.
The pH scale is a standard scale, which is used for measuring the approximate strength of an acid or an alkali solution.The pH scale has ranged from 1 to 14. Acidic solutions have a pH value less than 7while alkaline solutions have a pH value greater than 7. Distilled water has pH value 7 and is called neutral substance. Strong acids have pH value 1 or 2 while strong alkali's have pH value 13 or 14.
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