How many moles of NaOCl must be added to 150 mL of 0.025 M HOCl to...

Question

Question

How many moles of NaOCl must be added to 150 mL of 0.025 M HOCl to obtain a buffer solution with a pH = 7.50? Ka= 2.8×10^-8 for HOCl.

The answer is 3.3x10^-3

science chemistry

Answer 1

Answer #1

PKa = -logka

= -log2.8*10^-8

= 7.5528

no of moles of HOCl = Molarity * voluem in L

= 0.025*0.15 = 0.00375 moles

PH = PKa + log[NaOCl]/[HOCl

7.5 = 7.5528 + log[NaOCl]/0.00375

log[NaOCl]/0.00375 = 7.5-7.5528

log[NaOCl]/0.00375 = -0.0528

[NaOCl]/0.00375 = 10^-0.0528

[NaOCl]/0.00375 = 0.8855

[NaOCl ] = 0.88*0.00375

no of moles of NaOCl = 0.0033moles = 3.3*10^-3

Answer 2

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