Given the unknown acid titration curve, and the [NaOH] of 0.1248M, please determ
ID: 562620 • Letter: G
Question
Given the unknown acid titration curve, and the [NaOH] of 0.1248M, please determine the molar equivalencies of NaOH for each observed equivalence point, and determine whether the unknown acid is mono, di, or triprotic. Finally, please identify the weak acid according to calculated ka value (half-equivalence point is at 1.83ml of NaOH added).
Please explain your reasoning below and how you know it's one of either mono, di or triprotic, and definitely not the other. Thank you.
Figure 3 Titration of 0.1M Unknown Weak Acid (Mountain Dew) with 0.1M NaOH 9 28o 7-t 0.75 3 1 .83 2 3.65 4 6 Volume (mL)Explanation / Answer
At First half Equivalence point volume of NaOH used is 1.83mL
At First Equivalence point volume of NaOH used is 3.25mL
At second half Equivalence point volume of NaOH used is 3.65 mL
At second Equivalence point volume of NaOH used is 4.30mL
At third half Equivalence point volume of NaOH used is 4.55mL
At third Equivalence point volume of NaOH used is 5.80mL
The Above values Are Graphically visualised for example
Tripotic acid is the Unknown Acid Because it is only solution which maintains roughly pH=7
Therefore,Ka of Tripotic acid =1.38*10-7
pH=-log[H+]=pKa=-log[Ka]=7-log(1.38)=7-0.13=6.68.
Note:the Type of triprotic acid used above is dihydrogen phosphate.
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