ใบความรู้ทฤษฎีกรด-เบส

Exercise

1.Demonstrate that the dissolution of HNO3 in water is actually a Brønsted-
Lowry acid-base reaction by describing it with a chemical equation and
labeling the Brønsted-Lowry acid and base.

→Answer HNO3 + H2O H3O+ + NO3−; HNO3: Brønsted-

Lowry acid; H2O: Brønsted-Lowry base

2. Write a balanced chemical equation for the neutralization of
Ba(OH)2(aq) with HNO3(aq).

→Answer 2HNO3(aq) + Ba(OH)2(aq) Ba(NO3)2(aq) + 2H2Ov

3. Write the chemical equation of the reaction of ammonia in
water and label the Brønsted-Lowry acid and base.

→Answer NH3 + H2O NH4+ + OH−; NH3: Brønsted-Lowry base;

H2O: Brønsted-Lowry acid

Ms. Phattharaporn Promrukkachat M.5/5 No.35

-AAcciidd BBaassee RReeaaccttiioonnss

pH, Buffers, Acids, and Bases

Self-Ionization of WaterHydrogen ions are spontaneously generated
in pure water by the dissociation (ionization) of a small percentage of
water molecules into equal numbers of hydrogen (H+) ions and hydroxide
(OH–) ions. The hydroxide ions remain in solution because of their hydrogen
bonds with other water molecules; the hydrogen ions, consisting of naked
protons, are immediately attracted to un-ionized water molecules and form
hydronium ions (H30+). By convention, scientists refer to hydrogen ions and

⇋their concentration as if they were free in this state in liquid water.
2H2O H3O++OH­
The concentration of hydrogen ions dissociating from pure water is
1 × 10-7 moles H+ ions per liter of water. The pH is calculated as the
negative of the base 10 logarithm of this concentration:

pH=­log[H+]
The negative log of 1 × 10-7 is equal to 7.0, which is also known as
neutral pH. Human cells and blood each maintain near-neutral pH.

Types of acids and bases

Type of acid
1. Monoprotic acid breakdown1, is HNO3, HClO3, HClO4, HCN.
2. Diprotic acid breaks down 2, namely H2SO4, H2CO3.
3. Polyprotic acid breaks down 3 ie H3PO4.
Each polyprotic acid dissociation gives H + not the same, the first
will break very well, the Ka value is very high, but the subsequent
rupture will have a very low Ka value because the negative ions
in the ions attract H + as the equation.

H2SO4 H + + HSO4- Ka1 = 1011
HSO4- H + + SO42- Ka2 = 1.2 x 10-2
Since polyprotic acids are usually K1 >> K2 >> K3 H +, most
solutions are obtained from the first dissolution.If the K1 value is
greater than K2 = 103 times, the pH of the polyprotic acid solution
can be determined from the K1 value only, but if the K2 value is
not very low, the K2 value must be taken into account.

Bass type
Bases are classified according to the number of OH- in the base.
There are three types of bases:
1.Basses that have a single OH- like LiOH NaOH KOH RbOH CsOH.
2. Bases with OH- 2 such as Ca (OH) 2 Sr (OH) 2 Ba (OH) 2
3. Bases with OH- 3 such as Al (OH) 3 Fe (OH) 3

Strength of acids and bases

Strong acids are acids that are 100% dissociable in water, such
as HCl, H2SO4, HN03, HBr, HClO4, and HI.
The strong base (weak base) is an acid that is 100% dissociable
in water, such as Hydroxide of the elements group 1 and 2
(NaOH LiOH CsOH Ba (OH) 2 Ca (OH)2).
Weak acid is an acid that can be partially ionized, such as the
acetic acid in vinegar, aspirin (acetylsalicylic acid), used to relieve
headaches, saccharin is a sweetener, niacin (nicotinic acid). ) Or
vitamin B, etc. An example reaction of CH 3COOH acid solution
in a vinegar mixture is as follows:
CH 3COOH (aq) + H2O(1) H3O + (aq) + CH3COO -(aq) has k a.
A weak base is a base that can only partially disintegrate, for
example, NH 3 urea aniline, etc. An example of ammonia reaction
is as follows.

NH3 (aq) + H2O (aq) NH4 + (aq) + OH - (aq)

We need to know the direction of the balance shift first. So we can tell
about the strength
1.If balance is shifted to the right, CH3COOH is a stronger acid than
H3O + / H2O is a stronger base than CH3COO-.
2. If balance moves to the left H3O + is a stronger acid than CH3COOH /
CH3COO- It is a stronger base than H2O.

If the K> 1 equilibrium is shifted forward
(the product substance is greater than the reactant).
K <1 balance moves backward (less product substance than reactant)
K = 1 forward is equal to reverse (Product substance = reactant)
Both sides of the strength are the same.

eexxeerrcciissee

1.Write the chemical equation for the reaction that occurs when cocaine
hydrochloride (C17H22ClNO4) dissolves in water and donates a proton to a
water molecule. (When hydrochlorides dissolve in water, they separate into
chloride ions and the appropriate cation.)

Answer →C17H22NO4+ + H2O H3O+ + C17H21NO4

2.Explain what is occurring when a chemical reaction reaches equilibrium.

Answer The overall reaction progress stops because the reverse process
balances out the forward process.

3.For each combination in Exercise 3 that is a buffer, write the chemical
equations for the reactions of the buffer components when a strong acid and
a strong base is added.

Answer →3b: strong acid: H+ + NO2­ HNO2; strong base:
→OH­ + HNO2 H2O + NO2­;
→3d: strong acid: H+ + NH3 NH4+; strong base:
→OH­ + NH4+ H2O + NH3

Ms.Pawinee Suninbun M.5/5 No. 36











Acid-base

Arrhenius Concept

acid is a compound with H and dissolves in water to
H + or H3O.

Bases are OH-containing compounds and, when dissolved
iwater, breaks down to OH-.

Acid-base test

Clause 1 Which of the following substances or
ions can be both acids and bases?

1. H2O
2. HC2O4-
3. HS-
4. NO3-

Exam answers

4. NO3-

Acid-base test

Clause2 Which solution is the most acidic?

1 solution of concentrated hydrochloric acid 10-5 mol / l
2 solution with hydronium ions 10-2 mol / l.
3 pH 3 solution
4 pH 4 solutions

Exem Answers

2. Solution containing 10-2 mol / l hydronium ions.

Acid-base test

Clause 3 A solution of thick ammonia 0.10 mol / l has
a pH of 11, indicating that

1 pOH = 3

2 OH- has a concentration of 10-11 mol / l.
3 H + has a concentration of 10-3 mol / l

4 Ka of NH4 + = 1 * 10-5

Exem Answers
1.pOH = 3

Miss swita boonchwy No 38 Class5/5

ACID-BASE TITRATION

Acid-base titration refers to the quantification process. By using a
standard solution with known concentration values
Of course, the reaction with the sample. By relying on the reaction between
a solution of acid and base that reacts exactly Makes it possible to calculate
the concentration or quantity of the said sample
The acid-base titration method is to take the sample acid or base solution
For quantitative analysis. Let's titrate it with a base or standard acid solution
with a known concentration, ie if the sample is an acid solution. Would have to
use a standard solution as a base To be titrated And record the volumes of
the standard solution used in the reaction. Then to calculate the quantity of
the sample substance. Or the opposite If using the sample solution as a base
Would have to use a standard acidic solution

For example To determine the concentration of an HCl acid solution, a 0.100
mol / L NaOH standard solution may be titrated with a handful of HCl samples
(possibly 50 cm3) when the volume of NaOH used in the reaction is known. Fit
this 50 cm3 HCl, with the indicator indicating the end point. And then we can
calculate the concentration of the HCl acid.
Standard solution Who know the exact concentration It is contained in a
glassware called burette which has a closed-loop stopper to drop the
standard solution onto a conical flask containing the sample solution to be
analyzed in titration. Shake or turn the funnel-shaped bottle to mix well.
Tyrate until the indicator changes color, the titration stops. And record the
volume of standard solution used To be further calculated for solution pH

Oraya Tongnarin No. 39 M. 5/5

Acid-base exercises

1. Concentrated HBr solution 0.5 mol / dm3 ionizes only
0.2 mol / dm3.
A. 10
B. 20
C. 30
D. 40

2. 5 liter of HF solution contains 500 g of HF dissolution. What
ions are there? And what is the concentration (H = 1, F = 19)

A. H + and F- each of 5 mol / L each.

B. H3O + and F- each of 5 mol / L.

C. H + and F- each of 100 mol / L.

D. H3O + and F- each 100 mol / L each.

3. The hydrochloric acid solution has a concentration of 0.025
mol / dm3 and only 20% dissociates. What is the constant of
this solution?

A. 5x10-3

B.1.25x10-3

C. 8x102

D. 5x103

Oraya Tongnarin No. 39 M. 5/5

exercise answer

1. Concentrated HBr solution 0.5 mol / dm3 ionizes only
0.2 mol / dm3.

Answer D. 40
0.2 = x (0.5) / 100
X = 0.2 (100) /0.5
= 40

2. 5 liter of HF solution contains 500 g of HF dissolution. What
ions are there? And what is the concentration (H = 1, F = 19)

Answer B. 3O + and F- each of 5 mol / L
n=g/M
= 500/1 + 19
= 500/20
= 25 mol
C=n/v
= 25/5
= 5 mol / L

3. The hydrochloric acid solution has a concentration of 0.025
mol / dm3 and only 20% dissociates. What is the constant of
this solution?

Answer D. 5x10-3
= (20/100) (0.025)
= 0.2 (0.025)
= 0.005
= 5x10-3

Oraya Tongnarin No. 39 M. 5/5