Aquaoeus Solutions and Chemical Equilibria - Acids and Bases v.0.pdf

ANALYTICAL CHEMISTRY

1. Chemical
Equilibria and
Quotients
College of Engineering
Palawan State University
1
st
Semester 2024

2. The chemical composition of
aqueous solutions
Classifying Solutions of Electrolytes
•Electrolytes – are substances
that when dissolved in water
will dissociate into positively
charged and negatively
charged ions; which will have
the ability to conduct electricity
while in the solution.
•Substances that do not
dissociate are known as non-
electrolytes.

3. The chemical composition of
aqueous solutions
Classifying Solutions of Electrolytes
•Strong Electrolytes – those that ionize almost completely
/ dissociates at a greater degree in a solution.
•Weak Electrolytes – those that ionize partially in a
solution or can be interpreted as some of particles
dissociate while some do not.
•Non-electrolytes – have no ionization

4. The chemical composition of
aqueous solutions
Classifying Solutions of Electrolytes
These three can be distinguished by their electrical
conductivity.
•Strong Electrolytes
•Weak Electrolytes
•Non-electrolytes
The more ions there are in the solution, the greater the
conductivity and stronger the electrolyte.

5. The chemical composition of
aqueous solutions
Classifying Solutions of Electrolytes
KCl – example of a strong and ionic electrolyte (will dissociate entirely)Other Examples of strong
electrolytes:

6. The chemical composition of
aqueous solutions
Classifying Solutions of Electrolytes

7. The chemical composition of
aqueous solutions
Classifying Solutions of Electrolytes
HCl is a Covalent compound, only neutral compound, but once
dissolved in water it will become a HCl acid (a strong acid)

8. The chemical composition of
aqueous solutions
Classifying Solutions of Electrolytes
HCl is a Covalent compound, only neutral compound, but once
dissolved in water it will become a HCl acid (a strong acid)

9. The chemical composition of
aqueous solutions
Classifying Solutions of Electrolytes

10. The chemical composition of
aqueous solutions
Classifying Solutions of Electrolytes

11. The chemical composition of
aqueous solutions
Classifying Solutions of Electrolytes

12. The chemical composition of
aqueous solutions
Classifying Solutions of Electrolytes

13. The chemical composition of
aqueous solutions
Classifying Solutions of Electrolytes

14. The chemical composition of
aqueous solutions
Acids and Bases
•Brønsted-Lowry theory: any compound that can transfer
a proton to any other compound is an acid, and the
compound that accepts the proton is a base. Wherein a
proton is a nuclear particle with a unit positive electrical
charge; it is represented by the symbol H+ because it
constitutes the nucleus of a hydrogen atom.
(Encyclopedia Britannica)

15. The chemical composition of
aqueous solutions
Acids and Bases

16. The chemical composition of
aqueous solutions
Acids and Bases
•In the Lewis theory of acid-base reactions, bases donate
pairs of electrons and acids accept pairs of electrons.
ALewis acidis therefore any substance, such as the
H
+
ion, that can accept a pair of nonbonding electrons. In
other words, a Lewis acid is anelectron-pair acceptor.
ALewis baseis any substance, such as the OH
-
ion,
that can donate a pair of nonbonding electrons. A Lewis
base is therefore anelectron-pair donor.

17. The chemical composition of
aqueous solutions
Acids and Bases
•In the Lewis theory of acid-base reactions, bases donate
pairs of electrons and acids accept pairs of electrons.
ALewis acidis therefore any substance, such as the
H
+
ion, that can accept a pair of nonbonding electrons. In
other words, a Lewis acid is anelectron-pair acceptor.
ALewis baseis any substance, such as the OH
-
ion,
that can donate a pair of nonbonding electrons. A Lewis
base is therefore anelectron-pair donor.

18. The chemical composition of
aqueous solutions
Acids and Bases

19. The chemical composition of
aqueous solutions
Acids and Bases

20. The chemical composition of
aqueous solutions
Acids and Bases

21. The chemical composition of
aqueous solutions
Acids and Bases

22. The chemical composition of
aqueous solutions
Acids and Bases

23. The chemical composition of
aqueous solutions
Acids and Bases

24. The chemical composition of
aqueous solutions
Acids and Bases

25. The chemical composition of
aqueous solutions
Acids and Bases

26. The chemical composition of
aqueous solutions
Acids and Bases

27. The chemical composition of
aqueous solutions
Acids and Bases

28. The chemical composition of
aqueous solutions
Acids and Bases

29. The chemical composition of
aqueous solutions
Acids and Bases

30. The chemical composition of
aqueous solutions
Acids and Bases

31. The chemical composition of
aqueous solutions
Acids and Bases

32. The chemical composition of
aqueous solutions
Acids and Bases

33. The chemical composition of
aqueous solutions
Acids and Bases

34. The chemical composition of
aqueous solutions
Acids and Bases

35. SAMPLE PROBLEMS:
1.What is the pH of a 0.0235 M HCl solution?
2.What is the pOH of a 0.0235 M HCl solution?
3.What is the pH of a 6.50 x 10-3 M KOH solution?
4.What is the pH of a 6.2 x 10-5 M NaOH solution?
5.A solution with a H+ concentration of 1.00 x 10-7 M is
said to be neutral. Why?
6.A solution is created by measuring 3.60 x 10^-3 moles
of NaOH and 5.95 x 10^-4 moles of HCl into a container
and then water is added until the final volume is 1.00 L.
What is the pH of this solution?

36. SAMPLE PROBLEMS:
1.pH = -log[H+] = -log(0.0235) = 1.629
2.pH = -log[H+] = -log(0.0235) = 1.629 -> pOH = 14.000 – pH -> 14.000 – 1.629 = 12.371
3.pOH = -log[OH-] = -log(6.50 x 10-3) = 2.187 pH = 14.000 – pOH = 14.000 – 2.187 = 11.813
4.pOH = -log[OH-] = -log(6.2 x 10-5) = 4.21 pH = 14.00 – pOH = 14.00 – 4.21 = 9.79
5.The concentrations of H+ and OH- are equal, as are the pH and pOH, so the solution must
be neutral.

37. SAMPLE PROBLEMS:
6.

38. SEATWORK 1:
1.What is the pH of a 0.0045 M HNO₃ solution?
2.What is the pOH of a 0.0082 M NaOH solution?
3.A solution has a hydroxide ion concentration of 4.70 x 10⁻⁷
M. What is the pOH of the solution?
4.What is the pH of a 0.125 M HCl solution?
5.What is the pOH of a 0.030 M KOH solution (potassium
hydroxide is a strong base)

39. The chemical composition of
aqueous solutions
Acids and Bases
•We can assume that it would be completely ionized, but when
They only partially ionize and establish an equilibrium between
the ionized and unionized forms, hence we apply constants

40. The chemical composition of
aqueous solutions
Acids and Bases

41. The chemical composition of
aqueous solutions
Acids and Bases

42. The chemical composition of
aqueous solutions
Acids and Bases
•Make an Ice Box based on the given,

43. The chemical composition of
aqueous solutions
Acids and Bases
•Solve for the Hydronium concentration using the pH

44. The chemical composition of
aqueous solutions
Acids and Bases
•Apply computed concentrations in the ICE box, because we
know that the concentration of the products would be the same,
they would be equal. And as we can see the value of x is too
low, I would be negligible to deduct on the reactants side.

45. The chemical composition of
aqueous solutions
Acids and Bases
•We then can solve for Ka
•Based on that, we can solve for the degree of Ionization

46. SAMPLE PROBLEMS:
1.Calculate the Ka of HClO if the given pH of 0.100M
HClO is 4.23
2.Calculate the Ka value of a 0.2 M aqueous solution
of propionic acid (CH3CH2CO2H) with a pH of 4.88.
3.
A student has a 0.50M solution of acetic acid. She
adds solid sodium acetate until the concentration
of sodium acetate is 0.050M. What is the final pH of
the solution? The Ka for acetic acid is 1.8∗10−5.
Assume the volume remains constant.
4.Determine the equilibrium concentration of
CH3COO− ions in a 0.00270M CH3OOH solution.
Ka=1.76∗10^−5

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51. The chemical composition of
aqueous solutions
Buffer Solutions
•Buffer Solution – is a solution that can resist changes in
pH when limited amounts of acids and base are added
to it.

52. The chemical composition of
aqueous solutions
Buffer Solutions

53. The chemical composition of
aqueous solutions
Buffer Solutions
•Buffer solutions can be prepared using the

54. The chemical composition of
aqueous solutions
Buffer Solutions
•Using the formula for pH, we can derive the formula for
pKa of a certain acid:
•Thus, in order to create a buffer solution of a desired pH,
we must use an acid conjugate base pair where the pKa
is approximately equal to the pH

55. The chemical composition of
aqueous solutions
Buffer Solutions

56. The chemical composition of
aqueous solutions
Buffer Solutions

57. SAMPLE PROBLEMS:
1. A buffer is prepared containing 1.00 M acetic acid and
1.00 M sodium acetate. What is its pH?
2.A buffer is prepared containing 0.800 molar acetic acid
and 1.00 molar sodium acetate. What is its pH?
3.(a) Calculate the pH of a 0.500 L buffer solution
composed of 0.700 M formic acid (HCOOH, Ka = 1.77 x
10^-4) and 0.500 M sodium formate (HCOONa). (b)
Calculate the pH after adding 50.0 mL of a 1.00 M
NaOH solution.
4.0.1 mole of CH3NH2 (Kb = 5 x 10^-4) is mixed with
0.08 mole of HCl and diluted to one liter. What will be
the H+ concentration?

58. SAMPLE PROBLEMS:
6. Calculate the pH when 25.0 mL of 0.200 M acetic acid is
mixed with 35.0 mL of 0.100 M NaOH
7. Calculate the pH when 50.0 mL of 0.180 M NH3 is mixed
with 5.00 mL of 0.360 M HBr. (The Kb of ammonia is 1.77 x
10^-5.)
8. Determine the pH of a solution prepared by dissolving
0.35 mole of ammonium chloride in 1.0 L of 0.25 M
aqueous ammonia. Kb for ammonia equals 1.77 x 10^-5

59. SAMPLE PROBLEMS:

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