Basically need to know how to approach these, some solving strategy and how to a

Question

Basically need to know how to approach these, some solving strategy and how to answer them.

QUESTIONS 1. How much does the pH shift when 1 mL of 0.1 M NaoH is added to 10 mL of H20? Express your answer in + or - pH units 2. How much does the pH shift when 1 mL of 0.1 M NaoH is added to 10 mL of buffer? Express your answer in + or - pH units. 3. How much does the pH shift when 1 mL of 0.1 M HCI is added to 10 mL of H20? Express your answer in + or - pH units. 4. How much does the pH shift when 1 mL of 0.1 M HCI is added to 10 mL of buffer? Express your answer in + or - pH units. 5. Would the pH shift observed with the buffer have been greater, less, or the same if 0.4 M buffer had been used instead of 0.2 M buffer? (0.2 M Buffer was what was actually used.) Why? 6. Would the pH shift observed have been greater, less, or the same for the buffer if 1 M NaOH had been used instead of 0.1 M NaOH? Why?

Explanation / Answer

1. negative pH is not possible in water as a solvent. The range of pH in water is 0 to 14

0.1 M NaOH ph is 13

after addition of 10 mL water

m1v1=m2v2

0.1X1 = m2X10

m2 = 0.1/10

m2 = 0.01

pOH = -Log (OH)

pOH = -Log (0.01)

pOH = -Log (10-2)

pOH = 2

pH =14-pOH

pH =14-2

pH = 12

pH is decreased to one unit less after dilution with 10 mL water

2. buffer will not shift the pH it remains same, no change in pH

3. 0.1 M Hcl ph is 1

after addition of 10 mL water

m1v1=m2v2

0.1X1 = m2X10

m2 = 0.1/10

m2 = 0.01

pH = -Log (H+)

pH = -Log (0.01)

pH = -Log (10-2)

pH = 2

pH is increased to one unit more after dilution with 10 mL water

4. buffer will not shift the pH it remains same, no change in pH

5. A buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa. Its pH changes very little when a small amount of strong acid or base is added to it.

pH = pKa+log[acid or base/Salt]

pH is directly propotional to pKa

pKa = -log (ka)

Ka is directly proptional to concentration

if you use high concentrated buffer solution Ka value increase, hence pH will increase little.

but incase of 0.4 M buffer instead of 0.2 M it remains same.

6. if you use 1 M instead of 0.1 M the pOH of the buffer will increase due high dissociation constant. Hence pH will decrease

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