Download presentation

Presentation is loading. Please wait.

Published byGeoffrey Hudson Modified over 8 years ago

2
ACIDS AND BASES

3
Acid Base Titration A very accurate method to measure concentration. Acid + Base Salt + Water H + + OH - H 2 O Moles H + = Moles OH -

4
Buret Solution with Indicator

5
Acid-Base Titrations The amount of acid or base in a solution is determined by carrying out a neutralization reaction; an appropriate acid-base indicator (changes color in specific pH range) must be used to show when the neutralization is complete. This process is called a TITRATION: the addition of a known amount of solution to determine the volume or concentration of another solution.

6
3 steps… Add a measured amount of an acid of unknown concentration to a flask. Add an appropriate indicator to the flask (i.e. phenolphthalein) Add measured amounts of a base of known concentration using a buret. Continue until the indicator shows that neutralization has occurred. This is called the end point of the titration.

7
Example: A 25-mL solution of H 2 SO 4 is neutralized by 18 mL of 1.0 M NaOH using phenolphthalein as an indicator. What is the concentraion of the H 2 SO 4 solution? Equation: 2NaOH + H 2 SO 4 2H 2 O + Na 2 SO 4 How many mol of NaOH are needed for neutralization?

8
Example: A 25-mL solution of H 2 SO 4 is neutralized by 18 mL of 1.0 M NaOH using phenolphthalein as an indicator. What is the concentraion of the H 2 SO 4 solution? Equation: 2NaOH + H 2 SO 4 2H 2 O + Na 2 SO 4 How many moles of H 2 SO 4 were neutralized?

9
Example: A 25-mL solution of H 2 SO 4 is neutralized by 18 mL of 1.0 M NaOH using phenolphthalein as an indicator. What is the concentraion of the H 2 SO 4 solution? Equation: 2NaOH + H 2 SO 4 2H 2 O + Na 2 SO 4 Calculate the concentration of the acid:

10
Titration Curve: a graph showing how the pH changes as a function of the amount of added titrant in a titration. Data for the graph is obtained by titrating a solution an measuring the pH after every drop of added titrant.

11
Titration Curve: a graph showing how the pH changes as a function of the amount of added titrant in a titration. Equivalence point: the point on the curve where the moles of acid equal the moles of base; the midpoint of the steepest part of the curve (the most abrupt change in pH) is a good approximation of the equivalence point.

12
Titration Curve: a graph showing how the pH changes as a function of the amount of added titrant in a titration. Knowledge of the equivalence point can then be used to choose a suitable indicator for a given titration; the indicator must change color at a pH that corresponds to the equivalence point.

13
Calculations of Titrations

14
1) The Mole Method of Molarity: Calculate the molarity of a sulfuric acid solution if 23.2 mL of it reacts with 0.212 g of Na 2 CO 3. H 2 SO 4 + Na 2 CO 3 Na 2 SO 4 + CO 2 + H 2 O

15
2) Normality: The normality (N) of a solution is defined as the (M) x (total positive oxidation)

16
Examples: HCl H + + Cl - H 2 SO 4 2H + + SO 4 2- NaOH Na + + OH - Ba(OH) 2 Ba 2+ + 2OH - + ox = 1 + ox = 2 + ox = 1 + ox = 2

17
Example: Calculate the molarity and normality of a solution that contains 34.2 g of Ba(OH) 2 in 8.00 L of solution.

18
In titration problems, you can use this equation:

19
Example: 30.0 mL of 0.0750 N HNO 3 required 22.5 mL of Ca(OH) 2 for neutralization. Calculate the normality and molarity of the Ca(OH) 2 solution.

Similar presentations

© 2023 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google