Need help starting after graph, question 1 Date Name DATA SHEET: pH, BUFFERS AND

Question

Need help starting after graph, question 1 Date Name DATA SHEET: pH, BUFFERS AND K. UNKNOWN Part pH of your pH UNKNOWN using indicators pH number Color with unknown Color with pH Color with pH solution Solution Estimated pH of pH UNKNOWN solution Instructor: Circle Students answer and initial pH of pH UNKNOWN using pH paper: Part 2: The Titration of a STRONG ACID (HC) with NaoHusing pH meter a) pH of 25 mL distilled water (Measure volume with graduated cylinder) b) pH of 25 mL distilled water with 1 drop 1.0 M HCl c) pH of 25 ml distilled water with 10 drops i.0 M HCI (Note: [H] in 3c is about 10 times that of 3b) d Titration of solution c) with 1.0 M NaOH. 1 M NaOH added a) pH of 25 mL distilled water 1.0 MAcetic Acid. Titration of solution c) with 1.0 M NaOH. 1 M NaOH added

Explanation / Answer

1) difference in pH 2b and 2c

0.53

HCl is a string acid which dissoiates completely into H+ and Cl- in solution, whereas, acetic acid is a weak acid which dissociates only partially in solution. Thus the two pH 2c and 3c are different.

Between the said volume of NaOH addition, the solution acts as a buffer and thus any adiiton of base resists pH change.

In 4b again a weak acid is present which forms a buffer solution and thus the pH is not seen much upon addtion of acid.

Equation : A- + H+ <==> HA

molar mass of unknown acid = 0.93 g/0.1948 M x 12.4 ml = 385.010 g/mol

molarity of solution = 0.93/385.01 x 0.0124 = 0.195 M

pKa of unknown acid = pH at half-equivalence point = 4.03

pKa = -logKa

Ka = 9.33 x 10^-5

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