O PREPARATION WORKSHEET Name: Date: TA: Section: Answer the following questions
ID: 1025726 • Letter: O
Question
O PREPARATION WORKSHEET Name: Date: TA: Section: Answer the following questions using information obtained from lecture, the textbook, or lab manual. The responses will be collected at the beginning of recitation and checked at the start of your lab section for credit. 1. You have a solution of the weak acid HA and add some of the salt NaA to it. a. What are the major species in the solution? b. What do you need to know to calculate [H,0+] concentration and the pH of the solu- tion, and how would you use this information? C. How does the pH of the HA solution compare with that of the final mixture? Explain. 2. A good buffer has: (a) about equal quantities of weak acid and conjugate base present; (b) as well as having a large concentration of each species present. Discuss this statementExplanation / Answer
1)
a)
Major species are HA, H3O^+ or H+ ,A^- ,Na^+
b)
pH=pKa+log[salt]/[acid]
pH=pKa+log10[NaA]/[HA]
Therefore,to find pH,pKa or Ka (acid dissociation constant) need to be known.
c)
The pH of HA will be more than that of the mixture of HA and NaA due to common ion effect.
As NaA is added in the solution of HA,NaA dissociates completely into Na+ and A- and since HA is a weak acid its ionisation is further suppressed by presence of common ion A-
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