15.2 DETERMINING pH AND TITRATIONS. 15.2 What are 2 ways of determining the pH of a solution?

15.2DETERMINING pH AND TITRATIONS

15.2What are 2 ways of determining the pH of a solution?

15.2The pH of a solution can be determined by: Indicators are a combination of a weak acid and a

weak base that change colors at a certain pH (transition interval). Each indicator is unique in the colors that it shows. p. 513

15.2The pH of a solution can be determined by: Indicators are a combination of a weak acid and a

weak base that change colors at a certain pH (transition interval). Each indicator is unique in the colors that it shows. Universal indicator is a mixture of several different indicators, so it has a wide variety of colors.

pH meters are electrodes that measure the conductivity of a solution by using the [H3O1+].

15.2What is a titration?

15.2A titration is a controlled neutralization reaction.

Indicators or a pH meter are used to identify when neutralization occurs.

What is the equivalence point?



The equivalence point occurs when the number of H3O1+ equals the number of OH1-.

If an indicator is used in a titration, it must change color approximately at the pH of the equivalence point. (The end point is the volume where the indicator changes colors.)



The equivalence point occurs when the number of H3O1+ equals the number of OH1-.

If an indicator is used in a titration, it must change color approximately at the pH of the equivalence point. (The end point is the volume where the indicator changes colors.)

If a pH meter is used in a titration, it shows the changes in pH as the acid is slowly added to the base or vise versa.

15.2A titration graph can be used to determine the molarity

of an unknown acid or base.


of an unknown acid or base.

A strong acid with a strong base neutralizes around pH ____.

A strong acid with a weak base neutralizes _______________.

A weak acid with a strong base neutralizes _______________.

A weak acid with a weak base neutralizes ________________.


of an unknown acid or base.A strong acid with a strong base neutralizes around pH

7A strong acid with a weak base neutralizes below pH 7.A weak acid with a strong base neutralizes above pH 7.A weak acid with a weak base neutralizes anywhere.

TITRATION GRAPHS

The green arrows show equivalence point.

The purple arrows show the end point.

15.2Example 1: Solutions of sodium hydroxide are used to

unclog drains. A 43mL volume of sodium hydroxide was titrated with 32.0mL of 0.100M HCl. What is the molarity of the sodium hydroxide?

15.2Example 2: A volume of 25mL of 0.120M sulfuric acid

neutralizes 40mL of a sodium hydroxide solution. What is the concentration of the sodium hydroxide solution?

15.2Example 3: A titration was performed on 40.0mL of a

solution of aniline. The acid/base ratio is 1:1. The following data was collected:

A. Sketch a titration graphB. Identify the equivalence point.C. Is aniline an acid or base?D. Why did the pH change only slightly between 20

and 30 mL of added acid?E. What is the concentration of the aniline solution?F. From p. 513, what is the best indicator to use?

VOLUME OF 0.100M HCl ADDED (mL)

pH

0 11.5

10.0 10.0

20.0 9.4

30.0 9.3

40.0 8.8

45.0 7.9

48.0 6.6

50.0 5.2

51.0 2.3

52.0 1.9

CHAPTER 15 TEST15 multiple choice (4 points each)10 short answer (2 points each)5 short answer (4 points each)1 extra credit (4 points)

CHAPTER 15 TESTpH scalefinding pH or pOH from [H3O+] or [OH-]finding [H3O+] or [OH-] from pH or pOHusing Kw to find [H3O+] or [OH-]use [H3O+], pH, pOH, or [OH-] to determine acidity, basicity, or

neutrality2H2O H3O+ + OH-

neutralization reactions (moles of OH- must equal moles of H3O+)strong acid with strong basestrong acid with weak baseweak acid with strong base

titrationsfinding concentration from datafinding concentration from graphdeciding on appropriate indicatorsequivalence point

15.2 DETERMINING pH AND TITRATIONS. 15.2 What are 2 ways of determining the pH of a solution?

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