Abfite the name of different types of indicadors
Answers
Answer:
An indicator prepared from natural substances is known as natural indicator. Examples are Litmus, Turmeric, China rose petals, snowball plant, Red Cabbage and Grape Juice… . An indicator prepared from artificial substances is known as synthetic indicator Examples are Phenolphthalein and Methyl Orange.
Explanation:
Mark me as brainliest answer
Answer:
Universal indicator is a mixture of coloured compounds, which is used for simple testing of solutions. It is of no use for titrations as there are several colour changes that take place over a variety of pH values.
Universal indicator is also available in the form of test paper. This consists of strips of paper impregnated with universal indicator solution and dried. It may be used to test solutions or gases. To test gases the paper must be dampened previously wth a drop of water and then held in the gas.
top
Litmus
Litmus is a vegetable based dye that was used in schools before the advent of universal indicator. It has a simple colour scheme, in acids it turns red and in bases it turns blue, however the mid-point is not sharply defined and is unsuitable for titrations.
It is usually used in the form of paper impregnated with the litmus dye. This comes in two varieties, the red paper that is used to test for bases and the blue litmus paper that is used to test for acids.
Litmus paper when previously dampened can also be used to test for the acidity of gases.
top
Phenolphthalein
Phenolphthalein is an organic indicator with a pKa value of 9.3. It is red in bases and colourless in acids.
Although it has a complicated structure, the good news is that you don't need to know it! In basic solution the molecule loses a hydrogen ion and becomes a negative ion. This can be represented by the much simpler equation:
HIn H+ + In-
The molecular form of phenolphthalein is represented as HIn and the ionic form as In-.
When base is added it removes the hydrogen ions from the equilibrium and the equation moves to the right hand side. We see the colour of the anion, i.e. red.
One slight complication of phenolphthalein is that the colour tends to fade as new products are formed on standing. In titrations the readings at the end point should be taken fairly quickly if adding base to acid.
Phenolphalein is the indicator of choice when titrating weak acids with strong bases, for example, ethanoic acid with sodium hydroxide.
PLEASE MARK ME THE BRAINLIEST