Hello!
Can someone explain to me how to work through this problem? What exactly is a predominant species?
"A monoprotic weak acid, HA , is ionized according to the reaction
HA(aq)+H2O(l)↽−−⇀A−(aq)+H3O+(aq) pKa=3.61
where A− is the conjugate base to HA.
For this weak monoprotic acid, the predominant species present at pH 6.47 is unknown, charged, or neutral?"
Thank you!
HW Week 10 Achieve #13
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Re: HW Week 10 Achieve #13
When the pH = pKa of a weak acid, there are equal amounts of the neutral species (HA) and the charged, deprotonated species (A-) in the solution. When pH > pKa, A- is more predominant, and when pH < pKa, HA is more predominant.
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Re: HW Week 10 Achieve #13
If the pH of the solution is equal to the pKa of the weak acid, there are equal amounts of HA (neutral, protonated) and A- (charged, deprotonated). If pH value is greater than pKa, A- is more predominant. If pH value is lower than pKa, HA is more predominant. In this case, pH is 2.38 and pKa is 4.45. Therefore, pH value is lower and the HA species is more predominant (i.e. the neutral species).
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Re: HW Week 10 Achieve #13
When pH is greater than pKa the acid is negatively charged. A- is more predominant so it is charged.
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Re: HW Week 10 Achieve #13
When pH > pKa, that means [H+] is low (pH is inversely proportional to [H+]) so [HA] is low and [A-] is high, so [A-] would be the predominant species. And A- is negatively charged.
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