Question

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Part 3: Preparing and testing the carbonic acid/bicarbonate buffer 3) and 6) Buffer 0.1 MHCI A: Buffer A: Buffer

  

Answer 1

Q-6

	pH in Beaker A	pH in Beaker B
solution	initial	after 5 drops HCl	after 20 drops HCl	initial	after 5 drops NaOH	after 20 drops NaOH
Buffer	6.1	5.9	5.7	6.1	6.2	6.3
water	6.0	3.1	2.5	6.0	10.4

3. Which liquid showed more resistance to pH?

The correct answer is Buffer.

Because, for the buffer liquid, even after the addition of 5 drops or 20 drops of HCl the pH was changed very little. pH was changed from 6.1 to 5.7 with 20 drops of HCl

pH was changed from 6.1 to 6.3 with 20 drops of NaOH.

whereas water showed large variance of pH.

pH was changed from 6.0 to 2.5 with 20 drops of HCl

pH was changed from 6.0 to 10.4 with 5 drops of NaOH

4. The two active chemicals in buffer are weak acid + salt of weak acid and strong base

                                                          weak base + salt of weak base and strong acid

5. The mixture of weak acid + salt of weak acid and strong base in the case of acid buffer

(or) the mixture of weak base + salt of weak base and strong acid in the case of base buffer, is responsible for small pH change when HCl is added