Last modified: Wed 12/31/1969 06:00:00 pm
ACA

Oklahoma State University

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Answer all of the questions below. If you do not know an answer enter CNA. However, it will help me the most if you answer each question with your best intuition/idea about what would be a reasonable answer.


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Our discussion of acids and bases has prepared you to calculate the pH of the following solutions,

strong acids
weak acids
strong bases
weak bases
the salt of a strong acid and a strong base
the salt of a strong acid and a weak base
the salt of aweak acid and a strong base
common ion - weak acid and its conjugate base
common ion - weak base and its conjugate acid

A secret for calculating the pH of neutralization reactions/titration curves is recognizing which of the above solution is formed after mixing an acid and a base.

Here is an example of what I mean;

Predict the type of solution formed when 30.0 mL of 0.450 M NaOH is added to 15.0 mL of 0.800 M HCl.

To answer this question we write the neutralization equation and set up an ICF table. In an ICE table we have to work in moles of each component. So we must determine the moles of NaOH and HCl we have initially before any reaction occurs. Below is the completed ICF table.

 

NaOH

+

HCl

NaCl

+

H2O

Initial

0.0135 mol

0.012 mol

0

-

Change

-.012

-.012

.012

-

Ending

0.0013

0

.012

-

Looking at the the Final row we can make the following observations....

The final condition after the reaction occurs shows moles NaOH and the salt NaCl are present. Since the salt NaCl does not effect the pH of the solution only strong base is important in determining the pH of the solution. So mixing 30.0 mL of 0.450 M NaOH is added to 15.0 mL of 0.800 M HCl yields a solution of a strong base. We can calculate the pH of a strong base by taking the moles of the NaOH in the Final row and dividing by the total volume of the mixture and then doing the -log thing.

So now you try it....

1. Indicate what substances are present in the solution (Ending row) when, (NOTE: you must follow the procedure described above)

a) 30.0 mL of 0.100 M NaOH are mixed with 25.0 mL of 0.100 M HBr

b) 20.0 mL of 0.0372 M NaOH are mixed with 34.0 mL 0.0520 M HC2H3O2

c) 40.0 mL of 0.234 M NH3 are mixed with 34.0 mL 0.135 M HCl

2. For each case in Q1 after the mixtures have been prepared, indicate whether the solution is acidic, basic or neutral.

a)

b)

c)

2. Below is a figure showing two titration curves,

List some similarities and some differences in the solutions used to generate these titration curves. Use a) and b) to differentiate between the two systems.

Similarities :

Differences :

3. Below is a titration curve. What can you tell me about the solutions used to produce this titration curve?

4. Is there anything about the questions that you feel you do not understand? List your concerns/questions.

5. If there is one question you would like to have answered in lecture, what would that question be?