Table 2.1 class 10 science solutions belongs to chapter 2 Acids, Bases and Salts.In this post, we will discuss colour change of different solutions with given indicators.
We know that substances or solutions are classified as acids or bases and they show different colour change with different indicators.
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We have given following solutions to test with indicators and identify whether they are acids or bases.
Given solutions
| Solutions |
| HCl |
| H2SO4 |
| HNO3 |
| CH3 COOH |
| NaOH |
| Ca(OH)2 |
| KOH |
| Mg(OH)2 |
| NH4OH |
Table
| Sample solution | Red litmus solution | Blue litmus solution | Phenolphthalein solution | Methyl orange solution |
Solutions
Now, we take given solutions in separate watch glasses and add a few drops of indicators given in the table 2.1 and observe the change in the colour.
| Sample solution | Red litmus solution | Blue litmus solution | Phenolphthalein solution | Methyl orange solution |
| HCl | No change | Changes to red | Colourless | Changes to red |
| H2SO4 | No change | Changes to red | Colourless | Changes to red |
| HNO3 | No change | Changes to red | Colourless | Changes to red |
| CH3COOH | No change | Changes to red | Colourless | Changes to red |
| NaOH | Changes to blue | No change | Change to light pink | Change to yellow |
| Ca(OH)2 | Changes to blue | No change | Change to light pink | Change to yellow |
| KOH | Changes to blue | No change | Change to light pink | Change to yellow |
| Mg(OH)2 | Changes to blue | No change | Change to light pink | Change to yellow |
| NH4OH | Changes to blue | No change | Change to light pink | Change to yellow |
So given solutions show change in colour with indicator. We can classify them into acids and bases on the basis of colour change.
Observation
- HCl, H2SO4 , HNO3 and CH3COOH show no change in colour with red litmus solution.
- HCl, H2SO4 , HNO3 and CH3COOH show red colour with blue litmus solution.
- HCl, H2SO4 , HNO3 and CH3COOH remain colourless with phenolphthalein solution.
- HCl, H2SO4 , HNO3 and CH3COOH show red colour with methyl orange solution.
So, these solutions are acids.
- NaOH , Ca(OH)2 ,KOH , Mg(OH)2 , NH4OH show blue colour with red litmus solution.
- NaOH , Ca(OH)2 ,KOH , Mg(OH)2 , NH4OH show no change in colour with blue litmus solution.
- NaOH , Ca(OH)2 ,KOH , Mg(OH)2 , NH4OH show light pink colour with phenolphthalein solution.
- NaOH , Ca(OH)2 ,KOH , Mg(OH)2 , NH4OH show yellow colour with methyl orange solution.
So, these solutions are bases.
We know solutions that release hydrogen ions (H+) water are called acids and solutions that release hydroxyl ions (OH– ) in water are called bases.
Important Questions based
1.How do acids react with red litmus paper?
Ans – Acids do not react with red litmus paper.
2.Why does litmus turn red in acid?
Ans- Litmus is naturally blue or purple obtained by Phaeophyta (lichens).Hydrogen ions from acids react with blue litmus causing it to turn red.
3.What are acids and bases according to Arrhenius theory?
Ans – According to Arrhenius theory, Acids are the substances that release hydrogen ions in aqueous solutions and bases release hydroxyl ions.
4.What do all acids and bases have in common?
Ans – All acids and bases release ions in aqueous solution. Acids release hydrogen ions and bases release hydroxyl ions.
5.How do acids and bases react with each other?
Ans- Acids and bases neutralize each other and the reaction is called neutralisation reaction.in this reaction salt and water are formed.
6.What are indicators in acids and bases?
Ans- Indicators are the substances used to identify the given solution is acidic or basic. They change their colour on the basis of PH of the given solution.
7.Name the indicator used in table 2.1to classify the given solutions as acids or bases?
Ans – Red litmus, blue litmus , phenolphthalein and methyl orange
8.Which solutions turn red when added to blue litmus solutions?
Ans – HCl , H2SO4 , HNO3 and CH3COOH
9.How do acids react with phenolphthalein solution?
Ans- Acids remain colourless with phenolphthalein solution.
10.What is the characteristics of acids?
Ans- Acids release hydrogen ions(H+ ) in water.
11.What is the characteristics of bases?
Ans – Bases release hydroxyl ions (OH– ) in water.
MCQs
1.What colour change does red litmus solution when added into acids?
(a)Blue
(b)Red
(c)Yellow
(d)No change
Correct answer- (d) No change
2.Why does litmus solution turn red in the presence of an acid?
(a)Litmus naturally gets turn into red in acid
(b)Litmus absorbs hydrogen ions and turn into red.
(c)Litmus react with oxygen
(d)All of the above
Correct answer -(b)Litmus absorbs hydrogen ions and turn into red.
3.What do bases release in aqueous solutions according to Arrhenius?
(a)Oxygen ion
(b)Hydrogen ion
(c)Hydroxyl ion
(d)None of the above
Correct answer -(c) Hydroxyl ion
4.What is common characteristics of all acids and bases?
(a)They are colourless
(b)They release ions in aqueous solution
(c)They have sour taste
(d)They turn blue litmus into red
Correct answer-(b) They release ions in aqueous solutions
5.What is the name of reaction when acid reacts with base?
(a)Combination reaction
(b)Decomposition reaction
(c)Neutralization reaction
(d)Displacement reaction
Correct answer-(c) Neutralization reaction
6.Which solution turn red when added to blue litmus solution?
(a)Bases
(b)Acids
(c)Both
(d)None of the above
Correct answer-(b) Acids
7.How do acids react with phenolpthalein solution?
(a)Acids turn into pink
(b)Acids turn into red
(c)Acids remain colourless
(d)Acids turns into yellow
Correct answer-(c) acids remain colourless
8.What is the specific characteristics of all acids?
(a)Release hydrogen ions
(b)Release hydroxyl ions
(c)Have bitter taste
(d)All of the above
Correct answer -(a) release hydrogen ions
9.What is the specific characteristics of bases?
(a)Release hydrogen ions
(b)Release hydroxyl ions
(c)Have sour taste
(d)All of the above
Correct answer- (b) release hydroxyl ions