A 1.0l buffer solution contains 0.100 mol of hc2h3o2 and 0.100 mol of nac2h3o2. the value of ka for hc2h3o2 is 1.8*10-5. part a calculate the ph of the solution upon the addition of 0.015 mol of naoh to the original buffer.

Question

Vincent Curtis

Chemistry

4 April, 03:40

A 1.0l buffer solution contains 0.100 mol of hc2h3o2 and 0.100 mol of nac2h3o2. the value of ka for hc2h3o2 is 1.8*10-5. part a calculate the ph of the solution upon the addition of 0.015 mol of naoh to the original buffer.

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Cannon Singleton · Answer 1

There are two ways to solve this problem. We can use the ICE method which is tedious and lengthy or use the Henderson-Hasselbalch equation. This equation relates pH and the concentration of the ions in the solution. It is expressed as

pH = pKa + log [A]/[HA]

where pKa = - log [Ka]

[A] is the concentration of the conjugate base

[HA] is the concentration of the acid

Given:

Ka = 1.8x10^-5

NaOH added = 0.015 mol

HC2H3O2 = 0.1 mol

NaC2H3O2 = 0.1 mol

Solution:

pKa = - log (1.8x10^-5) = 4.74

[A] = 0.015 mol + 0.100 mol =.115 moles

[HA] =.1 - 0.015 = 0.085 moles

pH = 4.74 + log (.115/0.085)

pH = 4.87