chemistry for engineers

1. Chemistry for Engineering
Name: Rheymark R. Butron BSCE-1A
Assessment #3
Part A
1. What is pH?
It is a quantitative measurement of the acidity or basicityof aqueous or other
liquid solutions. Ph is really a measure of a relative amount of free hydrogen
and hydroxyl ions in the water.
2. What is pOH?
It is a measure of hydroxide ion (OH-) concentration. It is used to express
the alkalinity of a solution. Aqueous solutions at 25 degrees Celsius with
pOH less than 7 are alkaline, pOH greater than 7 are acidic and pOH equal
to 7 are neutral.
3. What is Ionic product of Water?
The products are a positively charged hydronium ion and a negatively
charged hydroxide ion. In pure water is 1.0 × 10 -14. is taken. An acidic
solution is a solution in which the concentration of hydrogen ions is greater
than the concentration of hydroxide ions.
4. What is Buffer Solution?
A buffer is an aqueous solution containing a weak acid and its conjugate
base or a weak base and its conjugate acid. A buffer's pH changes very
little when a small amount of strong acid or base is added to it. It is used to
prevent any change in the pH of a solution, regardless of solute.
Part B
1. What is an Indicator?
Any substance that gives a visible sign, usually by a color change, of the
presence or absence of a threshold concentration of a chemical species,
such as an acid or an alkali in a solution. An example is the substance called
methyl yellow, which imparts a yellow color to an alkaline solution.
2. What is Arrhenius theory of acid and base?
Arrhenius theory, Is introduced in 1887 by the Swedish scientist Svante
Arrhenius, that acids are substances that dissociate in water to yield
electrically charged atoms or molecules, called ions, one of which is a
hydrogen ion (H+), and that bases ionize in water to yield hydroxide ions
(OH−).
3. What is Bronsted-Lowry Theory of acid and base?
A Brønsted-Lowry acid is any species that can donate a proton (H +) to
another molecule. A Brønsted-Lowry base is any species that can accept a

2. proton from another molecule. In short, a Brønsted-Lowry acid is a proton
donor (PD), while a Brønsted-Lowry base is a proton acceptor (PA).
4. What is Lewis concept of acid and base?
In the Lewis theory of acid-base reactions, bases donate pairs of electrons
and acids accept pairs of electrons. A Lewis acid is therefore any
substance, such as the H+ ion, that can accept a pair of nonbonding
electrons. In other words, a Lewis acid is an electron-pair acceptor.
Part C
1. Explain the Bronsted-Lowry theory of acids and bases with examples.
a Brønsted-Lowry acid is a proton donor (PD), while a Brønsted-Lowry base
is a proton acceptor (PA). Thus H + is an acid by both definitions, and OH
− is a base by both definitions. A reaction with water is called hydrolysis; we
say that NH 3 hydrolyzes to make NH 4 + ions and OH − ions.
2. Explain the Lewis Concept of acids and bases with examples. Mention its
advantages also.
A Lewis acid is an electron-pair acceptor. A Lewis base is any substance,
such as the OH- ion, that can donate a pair of nonbonding electrons. A
Lewis base is therefore an electron-pair donor.
ADVANTAGES:
1. It explain the acid base reactions by way of electron transfer.
2. It gives an idea about the acidic character of substances that do not
contain hydrogen. The acidicnature of the following substances like BF3,
FeCl3, AlCl3 can be easily explained by this concept.
3. The neutralization of acidic oxides and basics oxides can also be easily
explained by this concept
CaO: + SO2 CaSO3
Acid Base
4. The concept can be easily understood.
The Lewis acid-base theory can also be used to explain why nonmetal
oxides such as CO2 dissolve in water to form acids, such as carbonic acid
H2CO3.
CO2(g) + H2O(l) H2CO3(aq)
3. Write a note on application of PH industries.
pH is more important in many industries to get high yield and the quality. pH
plays a vital role in the following industries.
1. Textile Industry:
In textile industry the pH of a dye has to be maintained otherwise
dying will not be uniform and permanent.
2. Sugar Industry:
The pH of the sugarcane juice should be maintained between 8 and
9. Otherwise crystallization of sugar will not be better.
3. Leather Industry:

3. The pH of solution for tanning purposes should be 2.5 to 3.5. if not,
the hides will putrify.
4. The pH of liquid chlorine is more effective in the ph range of 5 to 6.5 in
the water treatment.
5. The pH of the soil should be maintained for plants to grow and to get
better yield.
6. The pH of human blood is 7.2 if not it cause coagulation of a blood which
leads to death.
7. The pH of a gastric juice is 1.4 to 2. Otherwise it may cause vomiting and
stomach disorder.
8. Here are the industries were pH plays a vital role: paper industry, alcohol
industry, medicine and chemical industry, food production industry etc.
PROBLEMS:
SOLUTIONS:
1. pH=-log [H+]
=-log (2x10-4)
= -(-3.69897)
= 3. 698997
2. pH=-log [H+]
=-log (1x10-9)
= -(-9)
= 9
3. [H+] = 10-H
= 10-4.28
= 5.2481 X10-5M
4. [H+] = 10-H
= 10-11.5
= 3.1623 X10-12M