Problem: A 120.0 -mL buffer solution is 0.110 M in NH3 and 0.135 M in NH4Br. What mass of HCl can this buffer neutralize before the pH falls below 9.00?        

🤓 Based on our data, we think this question is relevant for Professor Rex's class at UCF.

FREE Expert Solution

Determine the moles of the weak acid and conjugate base:

moles NH3=120 mL (10-3 L1 mL)(0.110 mol1 L)=0.0132 mol

moles NH4+=120 mL (10-3 L1 mL)(0.135 mol1 L)=0.0162 mol

Construct an ICF Chart:

pH=pKa+log(NH3NH4+)

pKa=14-pKb

pKa=14-4.75=9.25

9=9.25+log(NH3NH4+)log(NH3NH4+)=9-9.25log(NH3NH4+)=-0.25

(NH3NH4+)=10-0.25(NH3NH4+)=0.5623(0.0132-x0.0162+x)=0.5623

(0.0132-x0.0162+x)=0.56230.5623(0.0162+x)=0.0132-x9.10926×10-3+0.5623(x)=0.0132-x0.5623(x)+x=0.0132-9.10926×10-31.5623x1.5623=4.09074×10-31.5623

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Problem Details

A 120.0 -mL buffer solution is 0.110 M in NH3 and 0.135 M in NH4Br. What mass of HCl can this buffer neutralize before the pH falls below 9.00?        

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Based on our data, we think this problem is relevant for Professor Rex's class at UCF.