THE ACID BASE CHEMISTRY
Q1. Fill in the blanks:
1. Most of the acidic substances are sour
in taste.
2. Phenolphthalein is synthetic
type of indicator.
3. The strength of basic substance is
represented by pH.
4. pH scale ranges from zero to fourteen.
5. Acids and bases neutralize each other
to form salt and water.
6. Sodium or potassium salts of higher
fatty acids are termed as soap.
7. In FeSO4. 7H2O.H2O
represents water of crystallization.
8. 10% NaCl is known as brine.
Q2. Name the carboxylic
acids present in
|
Acid
|
|
Acid
|
Tamarind
Butter
Roots of plant valerum
Lemon
|
Tartaric acid
Butyric acid
-------------
Citric acid
|
Milk
Orange
Red ants
Honey bee sting
|
Lactic acid
Citric acid
Formic acid
Formic acid
|
Q3. Write short notes
on
1. Indicators (with proper example).
Ans. The acidic and basic
nature of the compounds can also be indicated by some natural as well as
chemical substances. These substances are known as indicators.
·
Rose
petals
·
Turmeric
·
Beetroot
are natural indicators.
i.
Acid
– base indicators: Some chemical substances such as phenolphthalein, methyl
orange, eosin are synthetic indicators.
ii.
Olfactory
indicators: Substances whose odour changes in acidic or basic solution are
called olfactory indicator. An olfactory indicator works on the principle that
when an acid or base is added to it, then its odour cannot be detected.
Examples: onion and clove extract.
iii.
Universal
indicators: Universal indicator is a mixture of several indicators which gives
different colours at different pH values of the pH scale.
iv.
Uses
of indicators: The acidic or basic nature of a compound can be judged. It is
used in agriculture to determine the pH of the soil.
2. pH scale (with proper diagram).
Ans.
i.
The
pH scale helps in measuring the concentration of hydrogen irons in a substance.
ii.
The
pH scale has a range between 0 and 14.
iii.
pH
7 represents a neutral substance, i.e., a substance that is neither acidic nor
basic.
iv.
An
acidic substance has a pH value between 0 and 7. Whereas a basic substance has
a pH between 7 and 14.
v.
Lower
the pH of an acid, greater is the concentration of H+ ions, greater the pH of a
base, greater is the concentration of OH ions.
3. Water of crystallization (with proper
example)
Ans.
i.
Water
of crystallization is the fixed number of water molecules present in the
crystal structure.
ii.
For
example, chemical formula of hydrated copper sulphate is CuSO4.5H2O.
Copper sulphate has 5 molecules of water of crystallization.
iii.
Sodium
carbonate is Na2CO3.10H2O. Sodium carbonate
has 10 molecules of water of crystallization.
iv.
On
heating or on exposure to air, the above salts lose water of crystallization
and form anhydrous substances.
Q4. Answer the following:
1. How do metal carbonates react with
acids?
Ans. When a metal
carbonate or metal hydrogen carbonate reacts with an acid, it forms
corresponding salt and carbon dioxide gas.
2. Explain in detail about hydronium
ion.
Ans.
i.
The
strength of an acid is measured in terms of the extent of ionization of the
acid in aqueous solution.
ii.
Higher
the H+ ions concentration stronger is the acid.
iii.
Hydrogen
ion (H+) does not exist alone. H+ ion being unstable, it
combines with H2O to form hydronium ion (H3O+).
3. What is universal indicator? Does
Mg(OH)2 react with sodium hydroxide? If not, why?
Ans.
i.
Universal
indicator is an indicator which is a mixture of several indicators.
ii.
It
has a very wide range and can indicate pH value almost from 0 to 14.
iii.
When
one or two drops of universal indicator is added to a solution, it changes its
colour. This colour is matched against the colour on a standard colour chart
(usually given on its bottle) to find the pH, and the pH value can be read.
This indicates the strength of the solution too.
iv.
Universal
indicator is available as a solution or in the form of paper strips.
Mg(OH)2 does not react
with sodium hydroxide as both are bases.
4. State application (uses) of baking
soda.
Ans. Baking soda, also
called sodium bicarbonate (NaHCO3), has many applications.
i.
It
is used in preparing soft, fluffy food items such as loaves of bread, cakes and
dhokla.
ii.
Being
used to treat slightly alkaline hyperactivity in the stomach.
iii.
Its
solution is used in fire extinguishers to produce carbon dioxide and water.
Q5. How do acids and bases react with each other? What is the
name of the process? What product is obtained out of these reaction?
Ans.
i.
Acid
reacts with base to form salt and water.
ii.
It
is known that, acid generates H+ and base generates OH-
ions.
iii.
The
H+ ions of an acid and OH- ions of a base react with each
other to form unionized water. The process is termed as neutralization.
iv.
The
product obtained out of this reaction is salt and water.