please show work and explanations. please. - A flask contains 300 mL of 0.13 M p

ID: 785169 • Letter: P

Question

please show work and explanations. please.

- A flask contains 300 mL of 0.13 M phosphate buffer that has a pH of 7.5. What volume of 0.2 M

NaOH should be added to increase the pH to 7.4?

What is the pH of 20 mL of 0.14M acetic acid?

What is the pH of 40 mL of 0.14M acetic acid?

A flask contains 300 mL of 0.13 M phosphate buffer that has a pH of 7.5. What volume of 0.2 M HCl should be added to drop the pH to 6.7.

The formula we are going to use throughout this problem is :

pH = pKa + log phosphate/ acid

7.5= 7.2 + log phosphate / acid

phosphate / acid =10^-0..3= 0.5011
Phosphate + acid = 0.13

Solve the system
phosphate = 0.434 M
acid = 0.0867 M

moles phosphate = 300x 0.434/ 1000 = 0.1302
moles acid = 300x 0.0867/ 1000 = 0.02601

Moles H+ added = V x 0.2 / 1000 = 0.0002V

Total volume = (300 +V) ml

moles phosphate = 0.1302-0.0002V

moles acid = 0.02601 + 0.0002V

Concentration phosphate = (0.1302-0.0002V)/(300+V)

Concentratin acid = ( 0.02601 + 0.0002V)/(300+V)

pH=7.2 + log {(0.1302-0.0002V)/(300+V)}/{( 0.02601 + 0.0002V)/(300+V)}

6.7 =7.2 + log((0.1302-0.0002V)/( 0.02601 + 0.0002V))

(0.1302-0.0002V)/( 0.02601 + 0.0002V) = 0.316

0.122 =2.632*10^-4V

V = 463 mL

similarily for remaining

Actually space not sufficient

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