CHEM 1A Lecture Notes - Lecture 24: Stoichiometry, Equivalence Point, Sodium Hydroxide

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indigohare215

5 Dec 2017

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UCSB

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Chemistry and Biochemistry

Course

CHEM 1A

Professor

Joseph C A

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Chem 1a - lecture 24 - titration and buffers. Acetate ion produced by the neutralization becomes a part of the available acetate: Hc2h3o2(aq) + oh (aq) (cid:12206) c2h3o2(aq) + h2o(l) 40 ml di water + 2 ml 1. 0m naoh. 40 ml buffer solution + 2 ml 1. 0 m naoh. Step 1: let reaction, h+ with a or oh with ha, go to completion. Determine new concentrations of ha and a . Determine the ph of a solution when we mix 40. 0 ml 1. 0 m hcl and 30. 0 ml 1. 0 m. The endpoint and the equivalence points are not always the same. Titrate 25. 0 ml of 1. 0 m ch3cooh with 1. 0 m naoh. For 1. 0 m ch3cooh: initially ph = 2. 4. Draw the graph: ph vs volume of naoh added. Write the net ionic equation for the reaction that occurs during the titration: a) ch3cooh + na+ + oh- b) ch3cooh + oh c) ch3cooh + naoh .

Related Questions

NH3/NH4 buffer:

Mass NH4Cl used 1.3738g

volume NaOH used 21.2 ml

initial pH (0f the buffer) 9.6, pH after 1 drop HCl 9.03, pH after 10 drops HCl 8.91

Dilute NaOH solution

Initial pH 10.35

pH :1 drop HCl 10.21, 10 drops HCl 2.85

Acetate buffer (0.500)

Mass of CH3COONa * 3H2O 10.935

volume CH#COOH 44.3 ml

initial pH 4.89

1.0 ml of NaOH pH 4.93

initial volume 2.2

final volume 16.2

final pH 5.91

Acetate buffer (0.100)

Mass of CH3COONa * 3H2O 2.1603

volume CH3COOH 8.9 ml

initial volume 6.2

final volume 23.2

Initial pH 4.85

final pH 5.83

1. Show complete calculations for the buffering capacity of both the 0.500 M and 0.100 M acetate buffers.

2. Compare ability of your buffer solution to resist changes in pH with that of the strong base (NaOH). Why can the buffer resist the pH change? Comment on why NaOH does not function as a buffer.

3. How did the concentration of the buffers affect the buffering capacity? Explain your observations.

IV. Comparing Buffering Capacity

A. pH of Pure Water

i. Measure out 30.0 mL DI H2O into a beaker.

1. Calculate the expected pH of pure water. pH ________

2. Measured pH of pure water. pH ___3.88______

3. What is the percent error between the calculated and measured value? What are some of the possible sources of this error?

% error __________

B. pH of Water and Strong Acid

i. Measure out 30.0 mL DI H2O and 2.0 mL of 1.0 M HCl into a beaker.

1. Calculate the expected pH of this solution. pH _________

2. Measured pH of this solution. pH ___1.64______

3. What is the percent error between the calculated and measured value? What are some of the possible sources of this error?

% error ____

C. pH of Water and Strong Base

i. Measure out 30.0 mL DI H2O and 2.0 mL of 1.0 M NaOH into a beaker.

1. Calculate the expected pH of this solution. pH _________

2. Measured pH of this solution. pH __12.03_______

3. What is the percent error between the calculated and measured value? What are some of the possible sources of this error?

% error ____

D. pH of Buffer solution

i. Measure out 50.0 mL 1.0 M CH3COOH and 50.0 mL of 1.0 M NaCH3COO into a beaker.

1. Calculate the total volume. (include units) Vol __________

2. What is the concentration of acetic acid in this solution after mixing. (include units)

[CH3COOH] _________

3. What is the concentration of acetate ion in this solution after mixing. (include units)

[CH3COO-] ___________

4. Calculate the expected pH of this buffer solution. pH __________

5. Measured pH of this buffer solution. pH __4.56________

6. What is the percent error between the calculated and measured value? What are some of the possible sources of this error?

% error __________

E. pH of Buffer after the addition of the Strong Acid

Measure out 50.0 mL the buffer in part D and add 2.0 mL of 1.0 M HCl into a clean beaker.

1. Calculate the expected pH of this solution. pH _________

2. Measured pH of this solution. pH ____5.30_____

3. What is the percent error between the calculated and measured value? What are some of the possible sources of this error?

% error ____

F. pH of Buffer after the addition of the Strong Base

Measure out 50.0 mL the buffer in part D and 2.0 mL of 1.0 M NaOH into a clean beaker.

1. Calculate the expected pH of this solution. pH _________

2. Measured pH of this solution. pH _4.57________

3. What is the percent error between the calculated and measured value? What are some of the possible sources of this error?

% error ____

I need help with an equilibrium problem and pH. I don't get howyou get b.

CHEM 1A Lecture Notes - Lecture 24: Stoichiometry, Equivalence Point, Sodium Hydroxide

CHEM 1A Full Course Notes

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