Activity 2.10 Class 10 Science

This activity explains what happens when an acid or a base is added to water. We will find the answer to whether the temperature of the solution increases or decreases.

What happens when acid or base is added to water?

 

 

Aim of the activity

To observe the temperature change when acid or base is added to water.

 

Materials used in this activity

 

S. N.	Materials
1	10 mL of water
2	Beaker
3	`H_2SO_4`
4	`NaOH`   pellets
5	Glass rod
6	Gloves, goggles

 

 

Procedure

 

We take 10 ml of water in a beaker and add a few drops of concentrated H₂SO₄ to it, and swirl the beaker slowly. Now we observe the change in temperature by touching the base of the beaker.

Now, in another beaker, we add sodium hydroxide pellets to water and also observe the temperature change.

 

 

Observation

   1.  When conc. Sulphuric acid is added to water, and the temperature increases.

   2. When conc. Sodium hydroxide pellets are added to water, and the temperature increases.

 

The temperature of the beaker rises in both cases.

 

Explanation

When an acid is added to water, it gets ionized into ions like H+ and anions.

In this activity, we have taken `H_2SO_4`, which dissociates into ions

 

The hydrogen ions combine with water molecules to form the hydronium ions

 

So, the formation of a new bond between hydrogen ions and water molecules releases energy.

The heat is released as a result of the stronger attractions formed between the ions and water molecules compared to the original acid molecules.

 

Conclusion

We can conclude through this activity that when  

Dilution of H₂SO₄ and NaOH is an exothermic process.

 

Multiple Choice Questions

  1. What happens when concentrated sulphuric acid is added to water?

   a) Temperature increases

   b)     Temperature decreases

   c) No change

   d)     None of the above

Correct answer – (a ) Temperature increases

 2. What type of chemical reaction occurs when `H_2SO_4`  is added to water?

   a) Endothermic

   b)   Exothermic

   c) Neutral

   d) No reaction

Correct answer – (b) Exothermic  

   3. While diluting concentrated acid, we should always

   a) Always add water to acid

   b)    Always add acid to water

   c) Mix both at the same time

   d)  All of the above

Correct answer – (b) Always add acid to water

  4. What change in the temperature is observed when sodium hydroxide pellets in water?

   a) Decreases

   b)   Increases

   c) Remains the same

   d)     First increases and then decreases

Correct answer – (b) Increases

  5. The chemical reaction in which heat is released is called

   a) Exothermic reaction

   b)     Endothermic reaction

   c) Neutralization reaction

   d)    None of the above

Correct answer – (a) Exothermic reaction