eneral Chemistry 4th Edition University Science Books presented by Sapling Learm

Question

eneral Chemistry 4th Edition University Science Books presented by Sapling Learming Map Calculate the change in pH when 9.00 mL of 0.100 M HCKaq) is added to 100.0 mL of a buffer solution that is 0.100 M in NHs(ag) and 0.100 M in NH4CI(aq). A list of ionization constants can be found here. Number Calculate the change in pH when 9.00 mL of 0.100 M NaOH(aq) is added to the original buffer solution. Number Previous Give Up & View Sohtion e, Check Answer 0 Next Exit about us careers privacy policy terms of use contact us help MacBook 80 F3 43 F7 F8 F9 F5 F6 F4

Explanation / Answer

#According to the question;

As we know that;

pOH= pKb + log[(NH4+)/ (NH3)]
pKb of NH3 = 4.74

So,

By using haderson's equation;
Initial pOH = 4.74 + log(0.100/0.100) = 4.74
pH = 14 - 4.74 = 9.26
Moles NH4+ = moles NH3

=molarity*volume of solution in litres = 0.100*0.100

= 0.0100

Now,

HCl---------> H+(aq) + Cl-(aq)

Thus,

Moles H+ added = Molarity of HCl*volume of HCl solution in litres =0.1*0.009

= 0.0009
NH3 + H+ = NH4+

Then,
Moles NH3 = 0.0100 - 0.0009=0.0091
Moles NH4+ = 0.0100 + 0.0009 = 0.0109

Therefore,
pOH = 4.74 + log{0.0109/ 0.0091} = 4.82
pOH = 14 - 4.82 = 9.18

So,
pH = 9.26 - 9.18

=0.08

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