Chapman University tension Questions 18 Experiment l. During the procedure for t

Question

Chapman University tension Questions 18 Experiment l. During the procedure for the lab the pH meter was calibrated with a buffer solution that 1.0 pH unit higher than what the label indicates. a. For Part A-How will this affect the determination of the molar concentration of the weak acid? Explain. me wnowarunuwntvahwvn www4 be lower. b For Part B-Is the determined pKaofthe weak acid too low, too high or unaffected by the miscalibration? Explain. The defenwuned pka of weak aud would 2. In a lab, an old bottle of hydrochloric acid was found with an unknown concentration. A pH meter was used to determine the pH to be 0.94. sample? a. How many moles of the hydronium ion are present in a 100.0 mL 014 o llut MIL 1000 to completely b. What volume, in milliliters, of 0.095MNaoH would be required that it can be neutralize a 100.0 mL sample of the hydrochloric acid solution so M,V 83.3 83

Explanation / Answer

1.a) The PH meter readfs 1 unit more than the label indicates. This means an original PH x will be shown by x+1

This miscallibration will affect the determination of molar concentration of the acid. Molar concentration of the weak acid will be lower. As more the PH shown, lower is the H+ concentration and so lower is the molar concentration of the acid.

1. b) As we know from Henderson Heselbach equation that PH=Pka+log[salt]/[acid] where [acid]=low than expected,and PH value is shown higher at the same time so calculated Pka will be significantly higher.

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