2.1 ACID, BASIS AND SALTS
Important Notes:
Part 1
Q.
If someone in the family is suffering from a problem of acidity after
overeating, which of the following would you suggest as a remedy– lemon juice,
vinegar or baking soda solution?
Ans. If someone in the family is
suffering from a problem of acidity after overeating, we will suggest baking
soda solution as a remedy because the ability of acids is nullify by the base.
We know that Acid and Base nullify each other’s effect.
Q. Which property did you think of while choosing the remedy?
Ans. The ability of acids and bases to
nullify each other’s effect
Q. What do you mean by Acids? Give the
definition of strong acid and weak acid with example.
Ans.
Earlier Definition of Acid: - According to the ancient definition ‘The acids are sour in taste and turn the blue litmus to red.’
They produce hydrogen when they react with metals.
New Definition of Acid: - According to the Arhenius ‘The
acids are the substances that produce hydrogen ions H+ when
mixed with water.’ For ex. HCl
HCL (aq) ▬▬▬▬► H+
aq) + Cl – aq)
Examples of Acids:- Examples of acids are : Hydrochloric Acid (HCl) Sulphuric Acid (H2SO4),
Nitric Acid (HNO3), Carbonic Acid (H2CO3),
Acetic Acid (CH3COOH)
Strong
Acids: -
An
acid which completely ionized into ions and produced large numbers of H+
is called Strong Acids
OR
Which acids ionized fastly into the water is
known as Strong acids.
They completely ionized
in water and form large number of Hydrogen ions. Strong acids fully ionized
into aqueous solution.
For exe. Hydrochloric Acid
(HCl) Sulphuric Acid (H2SO4),
Nitric Acid (HNO3) etc.
Weak
Acids: -
An
acid which is partially ionized in water and produced less numbers of H+
is called Weak Acids
OR
Which acids ionized slowly into the water is
known as weak acids.
They do not completely
ionized in water and form a small number of Hydrogen ions. For exe. Carbonic Acid (H2CO3),
Acetic Acid (CH3COOH)
Concentrated Acid : Having
more amount of acid + less amount of water
Dilute Acid : Having more amount of water + less amount of acid
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BASES
Q. What do you mean by Base? Give the definition
of strong base and weak Base with example.
Ans.
Earlier Definition of Bases: - According to the ancient definition ‘The bases are bitter and salty in taste and turn the red litmus to
blue.’
New Definition of Bases: - According to the Arhenius ‘The
bases are the substances that produce hydroxyl ions OH– when mixed with water.’
For exe. NaOH
NaOH(aq) → Na+ +
OH– (aq)
Examples of Bases:- examples of acids are : NaOH (Sodium Hydroxide), KOH (Potassium Hydroxide), NH4OH
(Ammonium Hydroxide) Ca (OH) 2 (Calcium Hydroxide)
Strong
bases: -
A
base which is fully dissociated in water and produces a large number of OH-
ions is known as strong bases.
OR
Which base ionized fully into the water is known
as Strong bases.
They completely ionized
in water and form large number of Hydroxyl ions. Strong bases fully ionized
into aqueous solution. For example Sodium Hydroxide [NaOH] and Potassium
Hydroxide [KOH]
Weak Bases:
- A
base which is partially ionized in water and produced a small numbers of OH-
is known as weak bases.
OR
Which bases ionized slowly into the water is
known as weak bases.
They do not completely
ionized in water and form a small number of Hydroxyl ions. For exe. Ammonium Hydroxide [NH4OH] and Calcium
Hydroxide [Ca(OH)2 ]
Alkalis : These are bases which are soluble in water [NaOH, KOH, Ca(OH)2].
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01.
Give two difference between acidic and bases.
02.
You have been provided
with three test tubes. One of them contains distilled
water and the other two contain an acidic solution and a basic solution, respectively. If you are given
only red litmus paper, how will you identify the contents of each test tube?
Ans. Dip the given red litmus paper into the
all three test tubes in which test tube this red litmus convert into blue
contain basic solution. Now dip this blue litmus into remain two test tube in
which test tube this blue litmus convert again red is Acid. And remained
third test tube contains only distilled water.
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Q. What is pH scale? How can you distinguish
between acid and base by using the pH scale?
pH Scale :- The negative
logarithm (base 10) of hydrogen ion concentration in moles per litre is known
as pH scale.
It is denoted by 
.
.
We should mind that 
OR 
OR 
Acidic or basic pH:- if the pH value of a substance is less then 7. This substance will
acid and its concentration will decrease regularly 0 to 7.
At the point of 7 it
is neutral substance. If the pH value of the substance is more than 7. It will
a bases substances and its basicity will increased regularly 7 to 14.
0<Acid>7 = < 7 >= 7<Base>14
Litmus Paper:- It is a special types of paper obtain by lichen (Thallophytic) is known
as litmus paper. It is used to test the nature of a substance.
We can recognize the nature of the substance by the help of the litmus
colour. Its chart is given below.
Violet, Indigo, Blue
(V.I.B)
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Green
(G)
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Yellow, Orange, Red
(Y.O.R)
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Base
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Neutral
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Acid
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More than 14 to 7
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7
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Less than 7 to 0
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pH of Salts :
(i)
Strong Acid + Strong Base → Neutral Salt : pH = 7
(ii)
Salt of strong acid + Weak base → Acidic salt : pH < 7
(iii)Salt of strong base + Weak acid → Basic salt : pH > 7
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Importance of pH in daily life:- It plays an important role in daily life we can find its importance by
following heading.
Q. What is the importance of pH scale in daily
life? What is its important for plants, teeth, digestion and water?
Ans.
pH and Plants:- It should be a good pH range for fertility of soil. Plants did not grow
in the soil which is out of this pH range. So too much acidic or basicity is
harmful to plants. We should cultured by making a suitable range of soil pH.
If a farmer wants to remove the acidity of soil
he should mix lime or gypsum in the soil.
pH of water :- pH or water is more that 5.6, When pH of water is less than 5.6, it is
called acidic water.
When this types of water comes down with rain. This type of rain is
called Acid rain. Acid Rain is cause of pollution.
pH of Tooth Enamel:- it is the hardest substances in the body. It is made up of calcium
phosphate. It is insoluble in water. The
pH value of mouth is more than 5.6, if it comes down the bacteria’s
grows in acidic medium and decayed the tooth enamel. We should use the tooth
paste with base.
pH of Milk :- The pH of milk
is 6 so that it is acidic. The milk maid mixed some baking powder in it to
decrease the acidity. It took more time to convert it into curd.
pH of digestive system :- The pH of mouth and intestine is acidic. The acids of the mouth and
intestine helps in digestion of food.
When excess acid is
released into the stomach. It decreases the PH level of stomach. Due to it the
normal acidity increases. This stage is known as acidity.
We used Antacid to remove the acidity of stomach. Some Antacids are Milk
of magnesia (Magnesium oxide.), baking powder and Eno. All antacids are bases.
1. Plants and animals are pH sensitive
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• Our body works within the pH range of 7-7.8.
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• When pH of rain water is less than 5.6, it is called acid rain.
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2. pH of the soil
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• Plants require a specific pH range for their healthy
growth.
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3. pH in our digestive system
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• Our stomach produces HCl acid which helps in
digestion.
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• During indigestion, stomach produces more acid and
cause pain and irritation.
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• To get rid of this pain, people uses antacid (mild
base) like milk of magnesia [Mg(OH)2] to neutralize excess acid.
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4. pH change as cause of tooth decay
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• Tooth decay starts when pH of mouth is lower than
5.5.
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• Tooth enamel made up of calcium phosphate (hardest
substance in body) does not dissolve in water but corrodes when pH is lower
than 5.5 due to acids produced by degradation of food particles by bacteria.
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• Using toothpaste (generally basic) tooth decay can be
prevented.
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5. Self defence by animals and plants through chemical
warfare
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(a) Bee sting leaves an acid which cause pain and
irritation. Use of a mild base like baking soad on stung area gives relief.
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(b) Stinging hair of nettle leaves inject methanoic
acid causing burning pain. Rubbing with leaf of dock plant give relief.
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Antacids:- The substances which are used to remove the
acidity of stomach is known as antacids. These are bases which
neutralized the acidity of the stomach. Some Antacids are Milk of magnesia
(Magnesium oxide), baking powder and Eno.
¶ pH value of milk is less than 6 so that a milkman mixed baking powder to
increase the basicity of the milk. It took more time to convert it into
curd. If it comes down the milk will
turned sour.
¶ Honeybee releases a type of acid in the body which produces a type of
pain or burning. By using the baking soda or other bases we can find relax in
pain or burning.
¶ The sting of the Nettle plant had Methaneoic (formic) Acid. We used the
leaves of other plant Dock which grows near the Nettle to remove its paint. It
is the example of natural Neutralisation.
Q. Which
type of acid is finded in the following substances?
Ans.
Name of substances
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Acid
|
Vinegar
Tamarind
Orange, Lemon
Tomato
Curd, Sour milk
Ant, Natal’s Sting
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Acetic Acid
Tartaric Acid
Citric Acid
Oxalic Acid
Lactic Acid
Formic (Methaneoic)
Acid.
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1. You have two
solutions, A and B. The pH of solution A is 6 and pH of solution B is 8.
Which solution has more hydrogen ion concentration? Which of this is acidic
and which one is basic?
2. What effect does
the concentration of H+(aq) ions have on the nature of the solution?
3. Do basic solutions
also have H+(aq) ions? If yes, then why are these basic?
4.
Under what soil condition do you think a farmer would treat the soil of his
fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or
chalk (calcium carbonate)?
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Indicators:- The substances which are used to recognize the nature of other substances are called
indicators. Indicators are pigments or group
of pigments.
Indicators are of two
types
01)
Natural Indicators
02)
Synthetic (man made) Indicators
Natural Indicators: - Indicators that are used naturally to recognized the nature of the
substances is known as Natural Indicators. For exe. Red cabbage,
turmeric, petunia, zirconium etc.
Synthetic (Manmade) Indicators:- The man made Indicators that are used to recognized the nature of the
substances is known as synthetic Indicators. For exe. Litmus Paper,
methyl orange, phenol ptyalin etc.
Coloured Indicators: - The indicators which changed its colour into the acidic or basic medium
are known as coloured indicators. For exe. Litmus Paper, methyl orange, phenol
ptyalin etc.
Methyl Orange + Acid = pink colour
Turmeric + Base = brown red
colour.
Olfactory Indicators:- The indicators whose odour change in acidic or basic medium is known as
olfactory indicators. For exe. Onion, clove oil etc.
Property
|
Acids
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Bases
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Taste
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Sour
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Bitter
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Litmus
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Red
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Blue
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Methyl Orange
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Red
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Yellow
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Phenolphthalein
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Nill
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Pink
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Natural indicators
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Synthetic indicators
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Olfactory indicators
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Found in nature in plants.
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These are chemical substances.
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These substances have different odour in acid and bases.
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Litmus, red cabbage leaves extract, flowers of hydrangea plant, turmeric
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Methyl orange, phenolphthalein
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S.N.
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Indicator
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Smell / Colour in acidic solution
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Smell / Colour in basic solution
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Natural indicators
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01
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Litmus
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Red
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Blue
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02
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Red cabbage leaf extract
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Red
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Green
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03
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Flower of hydrangea
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Blue
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Pink
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04
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Plant Turmeric
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No change
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Red
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Synthetic indicators
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01
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Phenolphthalein
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Colourless
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Pink
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02
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Methyl orange
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Red
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Yellow
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Olfactory indicators
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01
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Onion
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Characteristic smell
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No smell
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02
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Vanilla essence
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Retains smell
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03
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Clove oil
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Retains smell
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Loses smell
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For Full Chapters Detail With Note Read our
*Vinjeet Science Class 10*
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