Problem: How much solid NaCH3CO2•3H2O must be added to 0.300 L of a 0.50-M acetic acid solution to give a buffer with a pH of 5.00?

🤓 Based on our data, we think this question is relevant for Professor Clements' class at GWU.

FREE Expert Solution

Use Henderson-Hasselbalch Equation to calculate for pH for buffers:


pH=pKa+logconjugate baseweak acid

  • HCH3CO→ weak acid (acetic acid)
  • NaCH3CO→ salt of conj. base
    • from NaCH3CO2•3H2O


Molarity (M)=molL

moles HCH3CO2 =0.50 mol HCH3CO2 L (0.300 L)

moles acetic acid = 0.15 mol 


Ka for acetic acid:  Ka = 1.8 x 10-5



pKa=-log Ka


pH=-log Ka+log conjugate baseweak acid5.00=-log 1.8×10-5+log moles CH3CO2- 0.15 mol HCH3CO25.00=4.745+log (moles CH3CO2- 0.15 mol HCH3CO2)5.00-4.745=log (moles CH3CO2- 0.15 mol HCH3CO2)100.255=10log (moles CH3CO2- 0.15 mol HCH3CO2)1.8=(moles CH3CO2- 0.15 mol HCH3CO2)moles CH3CO2-=1.8(0.15 mol HCH3CO2)

moles CH3CO2- = 0.27 mol

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Problem Details

How much solid NaCH3CO2•3H2O must be added to 0.300 L of a 0.50-M acetic acid solution to give a buffer with a pH of 5.00?

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Based on our data, we think this problem is relevant for Professor Clements' class at GWU.

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Our data indicates that this problem or a close variation was asked in Chemistry - OpenStax 2015th Edition. You can also practice Chemistry - OpenStax 2015th Edition practice problems.