Activity 2.9 Class 10 Science

 This activity belongs to chapter 2 Acids, Bases and Salts Class 10 Science

Do All Acids Produce Ions only in Aqueous Solution?

Aim of the activity

To observe what happened to an acid or a base in water solution and find if acids produce ions only in aqueous solution.

Material used in the activity

1.  Solid sodium chloride (NaCl) 1 g

2.  Concentrated sulphuric acid

3.  Test tubes

4.  Blue Litmus paper

5.  Delivery tube

6.  Dropper

7.  Clamp stand

8.  Guard tube containing `CaCl_2`

 

Procedure

 We take  about 1g solid `NaCI` in a clean and dry test tube and set up the apparatus. We then add some concentrated sulphuric acid to the test tube. As the reaction begins, a gas evolve and come out of the delivery tube.

We bring a dry blue litmus paper strip close to the mouth of the delivery tube and observe any colour change.

Next, we bring a moistened blue litmus paper strip close to the mouth of delivery tube and observe the colour change.

Note to teachers : If the climate is very humid, you will have to pass the gas produced through a guard tube (drying tube) containing calcium chloride to dry the gas].

Observation

A colourless `HCl` gas evolve on the reaction of `NaCl` and `H_2SO_4`.

 

When we bring dry blue litmus paper near the opening of the calcium chloride tube, colour of the litmus paper remains unchanged.

But when we bring a moistened blue litmus paper near the mouth of delivery tube, blue litmus changes to red.

Explanation 

`HCl` gas is produced on the reaction of `NaCl` and `H_2SO_4`.

`NaCl + H_2SO_4 → NaHSO_4 + HCl↑`

This HCl gas does not show any effect on dry blue litmus paper. But it ionize with wet blue litmus paper and the blue litmus paper changes to red

`HCl + H_2O → H_3O^+ + Cl^-`

 

Conclusion

Dry `HCI` gas has no effect on dry  blue litmus paper. But in the presence of moisture, hydrogen chloride gas turns blue litmus to red. Thus `HCI` gas shows its acidic character only in presence of water.

Frequently Asked Question

1.  Why does dry `HCl` gas not show acidic character?

Dry `HCl` gas does not produce ions so it does not show acidic character.

2.  What type of reaction occurs between `NaCl` and `H_2SO_4`?

The reaction is double displacement reaction.

3.  Can this activity be performed with other acids?

Yes , this activity can be performed with other acids also because all acids release ions in water.

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