Activity 2.6 Class 10 Science

 This activity 2.6 has been taken from chapter 2 Acids, Bases and Salts in which we will discuss the reaction between acids and baes.

 

How do Acids and Bases React with each other?

Aim of the activity

To observe the neutralization reaction of acids and bases using an indicator.

Materials used in the activity

1.  2mL Sodium hydroxide solution

2. 2mL Hydrochloric acid

3. Phenolppthalein

4. Test tubes

5. Dropper

Procedure

We will perform this activity in the following steps.

Step 1- We will take 2mL solution of sodium hydroxide (NaoH) in a test tube and add few drops of an indicator Phenolphthalein and observe the change in colour of indicator.

Step 2- Now we add few drops of Hydrochloric acid (HCl) in the above mixture(in step 1) and observe any change.

Step 3-  Now we add few drops of sodium hydroxide solution in the above mixture (step 2) and observe change in colour of the mixture.

 

Observation

We will observe the changes in three following steps

Step 1 - When phenolphthalein is added to sodium hydroxide, it turns pink.

Step 2- When hydrochloric acid is added to the above solution, the pink colour disappears.

Steps 3- When sodium hydroxide is added to the above mixture, pink colour reappears.

Explanation

Phenolphthalein is an acid-base indicator. It shows pink colour in basic solution and become colourless in acidic solution.

When phenolphthalein is added to sodium hydroxide (basic solution) ,it turns pink.

 When  HCl is added to this , pink colour disappears. Acid and base reacts to form salt and water, this is called a neutralization reaction. Due to decrease in P^H , pink colour of phenolphthalein disappears.

`NaOH + HCl →NaCl + H_2O`

When sodium hydroxide is added again to this solution, the pink colour reappears.

Conclusion

This activity demonstrates the neutralization reaction between acid and base. Both acid and base destroy the effect of each other. Phenolphthalein helps indicate the reaction by changing in colour.

 

Frequently Asked Questions

1.  What is a neutralization reaction?

A neutralization reaction occurs when an acid and base react to produce salt and water.

2.  Why does phenolphthalein change in colour in this activity?

 Phenolphthalein is pink in basic solution and colouless in acidic solution. This happens due to change in the P^H of the solution.

3.  What happens if excess of hydrochloric acid is added?

 There is no change in colour because the solution become more strong by adding excess HCl.

4.  Can other indicators be used in this activity?

Yes, we can use methyl orange and litmus solutions in this activity.

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