Calculate the pH after adding 5.00 mL of 0.15 M HNO3 to 250 mL of an...

Calculate the pH after adding 5.00 mL of 0.15 M HNO₃ to 250 mL of an acetic acid/acetate buffer with an initial pH of 4.32 and a total buffer concentration of 0.25 M. Neglect activity coefficients for this problem.

Solutions

Expert Solution

Moles of HNO3 added =0.15 mol/L *5mL/1000mL = 0.00075 moles

Calculate the moles of acetate and acetic acid initially present. pka of acetate buffer = 4.76 (refer to your textbook)

pH = pka + log [salt/acid]

4.32 = 4.76 + log [salt/acid]

[salt/acid] = 0.36

decimal fraction of salt = 0.36/ 1+ 0.36 = 0.26

decimal fraction of acid = 1/1+ 0.36 = 0.74

Molarity of acetate =0.26 *0.25 = 0.065 M

Number of moles of acetate = 0.065 M * 250mL/1000mL = 0.016 moles

Molarity of acetic acid = 0.74 * 0.25 M

Number of moles of acetic acid = 0.74 * 0.25 M * 250mL/1000mL = 0.046 moles

HNO3 added will react with acetate to convert it to acetic acid. So, you have to substract the number of moles of acetate and add it to number of moles of acetic acid.

Moles of acetate after adding HNO3 = 0.016 moles - 0.00075 moles = 0.015 moles

Molarity of acetate in after adding HNO3 = 0.015 moles *1000ml/(5 + 250mL) = 0.059 M

Moles of acetic acid afetr adding HNO3 = 0.046 + 0.00075 =0.047 moles

Molarity of acetic acid after adding HNO3 = 0.047 /0.255 L = 0.18 M

pH = pKa + log [salt/acid]

= 4.76 + log [0.059/0.18] = 4.28

ph of the medium will be 4.28.

queen_honey_blossom answered 1 year ago

Next > < Previous

Related Solutions

Calculate the pH after adding 10.00 mL of 0.15 M HCl to 50 mL of the...

Calculate the pH after adding 10.00 mL of 0.15 M HCl to 50 mL of the ammonia/ammonium ion buffer solution with a ph of 4.82

(50 mL of 0.02000 M KOH Titrated with 0.1000M HBr) Calculate pH after adding the following...

(50 mL of 0.02000 M KOH Titrated with 0.1000M HBr) Calculate pH after adding the following volumes of the titrant: (a) 3 mL (b) 10 mL (c) 10.5 mL Answers: (a) pH =12.12; (b) pH = 7.00; (c) pH = 3.0. I need a step-by-step explanation on how to do this.

1. Calculate [OH−] for a solution formed by adding 5.00 mL of 0.120 M KOH to...

1. Calculate [OH−] for a solution formed by adding 5.00 mL of 0.120 M KOH to 20.0 mL of 7.1×10−2 M Ca(OH)2. 2. Calculate pH for a solution formed by adding 5.00 mL of 0.120 M KOH to 20.0 mL of 7.1×10−2 M Ca(OH)2. 3. Pyridine is a weak base that is used in the manufacture of pesticides and plastic resins. It is also a component of cigarette smoke. Pyridine ionizes in water as follows: C5H5N+H2O⇌C5H5NH++OH− The pKb of pyridine...

What is the pH after adding 10.0 mL of 0.10 M HCl to a 90.0 mL...

What is the pH after adding 10.0 mL of 0.10 M HCl to a 90.0 mL buffer solution of 0.60 M CH3COOH and 0.40 M CH3COONa at 25 °C? (Ka = 1.8 x 10−5)? What reaction will occur when HCl is added to the above buffer? 1) How many moles of acetic acid are present after the reaction? 2) How many moles of acetate ion are present after the reaction? 3) What is the concentration (in M) of acetic acid...

Your TA needs to make 250 ml of 0.15 M phosphate buffer (pH 7.2), but the...

Your TA needs to make 250 ml of 0.15 M phosphate buffer (pH 7.2), but the pH meter is not available. How much of each chemical (acid and conjugate base) should you weigh out to come close? MW of KH2PO4=136 K2HPO4=174

A 100.0 ml buffer solution is 0.20 M HC7H5O2 and 0.15 M NaC7H5O2. Calculate the pH...

A 100.0 ml buffer solution is 0.20 M HC7H5O2 and 0.15 M NaC7H5O2. Calculate the pH of the solution after the addition of 0.0025 moles of NaOH. Assume the volume of the buffer does not change. (HC7H5O2 = Ka 6.5x10^-5)

A 50.0-mL volume of 0.15 M HBr is titrated with 0.25 M KOH. Calculate the pH...

A 50.0-mL volume of 0.15 M HBr is titrated with 0.25 M KOH. Calculate the pH after the addition of 13.0 mL of KOH. Express your answer numerically. A 75.0-mL volume of 0.200 M NH3 (Kb=1.8×10−5) is titrated with 0.500 M HNO3. Calculate the pH after the addition of 15.0 mL of HNO3. Express your answer numerically. A 52.0-mL volume of 0.35 M CH3COOH (Ka=1.8×10−5) is titrated with 0.40 M NaOH. Calculate the pH after the addition of 33.0 mL...

3. Find the pH of… A) 0.0055 M HBr B) 5.00 ml of LiOH after it...

3. Find the pH of… A) 0.0055 M HBr B) 5.00 ml of LiOH after it is diluted to 500 ml C) 2.00 M sodium benzoate (Kb = 1.5 x 10 -10) E) Identify as acidic, basic or neutral: KNO3 NaF NH4Cl

Calculate the change in pH to 0.01 pH units caused by adding 10. mL of 3.30-M...

Calculate the change in pH to 0.01 pH units caused by adding 10. mL of 3.30-M NaOH is added to 650. mL of each of the following solutions. a) water pH before mixing = pH after mixing= pH change = b) 0.135 M NH41+ pH before mixing = pH after mixing= pH change = c) 0.135 M NH3 pH before mixing = pH after mixing= pH change = d) a buffer solution that is 0.135 M in each NH41+ and...

Calculate the change in pH to 0.01 pH units caused by adding 10. mL of 3.69-M...

Calculate the change in pH to 0.01 pH units caused by adding 10. mL of 3.69-M NaOH is added to 530. mL of each of the following solutions. a.) water pH before mixing: 7.00 (correct) pH after mixing: ?? b.) 0.180 M NH3 pH before mixing: 11.26 pH after mixing: ?? Thank you! Sincerely, a confused college student

Subjects