iPad 10:18 PM * 50% Chapter 17 Homework Set A: Attempt1 Question Completion Stat
ID: 1031326 • Letter: I
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iPad 10:18 PM * 50% Chapter 17 Homework Set A: Attempt1 Question Completion Status: 5.00000 points Save Answer UESTION 4 What is the pH of a buffer made by combining 10.0mL of 0.84 M CH3NH2 with 10.0 mL of 0.86 M CH3NH3CI? Kb CH3NH2-44x 104 5.00000 points Save Answer UESTION 5 What is the pH of a buffer made by combining 0.51 mol of CsHsN with 0.82 mol of C5H5NHBr in 100.0 mL of solution? Kb C5H5N 1.7x 10-9 Click Save and Submit to save and submit. Click Save All Answers to save all answers Save All Answers Close Window Save and SubmitExplanation / Answer
4)
Concentration after mixing = mol of component / (total volume)
M(CH3NH2) after mixing = M(CH3NH2)*V(CH3NH2)/(total volume)
M(CH3NH2) after mixing = 0.84 M*10.0 mL/(10.0+10.0)mL
M(CH3NH2) after mixing = 0.42 M
Concentration after mixing = mol of component / (total volume)
M(CH3NH3+) after mixing = M(CH3NH3+)*V(CH3NH3+)/(total volume)
M(CH3NH3+) after mixing = 0.86 M*10.0 mL/(10.0+10.0)mL
M(CH3NH3+) after mixing = 0.43 M
Kb = 4.4*10^-4
pKb = - log (Kb)
= - log(4.4*10^-4)
= 3.357
use:
pOH = pKb + log {[conjugate acid]/[base]}
= 3.357+ log {0.43/0.42}
= 3.367
use:
PH = 14 - pOH
= 14 - 3.3668
= 10.6332
Answer: 10.63
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