Class 9 Acids, Bases and Salts question answer maharshtra board
Acids, Bases and Salts class 9 exercise answers Maharashtra board | Acids, Bases and Salts 9 solution state board. | 9 class science and technology guide pdf Maharashtra board.
Q.1. Identify the odd one out and justify.
(a) Chloride, nitrate, hydride, ammonium
Answer:
Ammonium ( others areanions.)
(b) Hydrogen chloride, sodium hydroxide, calcium oxide, ammonia
Answer:
Hydrogen chloride ( Others are bases.)
(c) Acetic acid, carbonic acid, hydrochloric acid, nitric acid
Answer:
Acetic acid ( Others are inorganic acids)
(d) Ammonium chloride, sodium chloride, potassium nitrate, sodium sulphate
Answer:
Ammonium chloride ( Others are neutral salts.)
(e) Sodium nitrate, sodium carbonate, sodium sulphate, sodium chloride
Answer:
sodium carbonate ( Others are neutral salts)
(f) Calcium oxide, magnesium oxide, zinc oxide, sodium oxide.
Answer:
zinc oxide ( Others are basic oxides)
(g) Crystalline blue vitriol, crystalline common salt, crystalline ferrous sulphate, crystalline sodium carbonate.
Answer: crystalline common salt ( Others are
crystalline substances contain water of crystallization)
(h) Sodium chloride, potassium hydroxide, acetic acid, sodium acetate.
Answer:
acetic acid ( others are electrolytes)
2.Write down the changes that will be seen in each instance and explain the reason behind it.
(a) 50ml water is added to 50ml solution of copper sulphate.
Answer:
When 50ml water is added to 50 ml solution of copper sulphate, the blue colour
of aqueous solution of copper sulphate fades and also the concentration of
copper sulphate solution decrease.
(b) Two drops of the indicator phenolphthalein were added to 10ml solution of sodium hydroxide.
Answer:
When two drops of the indicator phenolphthalein were added to 10 ml of NaOH, it
develops light pink colour.
(c) Two or three filings of copper were added to 10ml dilute nitric acid and stirred.
Answer:
When two or three fillings of copper were added to 10 ml dilute nitric acid, it
forms copper nitrate and hydrogen gas.
(d) A litmus paper was dropped into 2ml dilute HCl. Then 2ml concentrated NaOH was added to it and stirred.
Answer:
A piece of litmus paper was added into 2 ml dilute HCl, blue litmus turns red.
When I n the same solution 2 ml concentrate NaOH was added and stirred, then
the red litmus turned blue.
(e) Magnesium oxide was added to dilute HCl and magnesium oxide was added to dilute NaOH.
Answer:
1)When magnesium oxide was added to dil. HCl , it forms magnesium chloride and water. Magnesium oxide being basic in nature it neutralizes acid.
2)There
is no reaction between magnesium oxide and dil. NaOH, as both are basic in
nature.
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(f) Zinc oxide was added to dilute HCl and zinc oxide was added to dilute NaOH.
Answer:
When zinc oxide was added to dilute HCl, it forms zinc chloride and water. In
this reaction, zinc oxide is a basic oxide. When zinc oxide was added to dilute
NaOH, it forms sodium zincate and water. In this reaction, zinc oxide is an
acidic oxide. Therefore, zinc oxide is an amphoteric oxide because it shows
both acidic and basic properties.
(g) Dilute HCl was added to limestone.
Answer:
When
dilute HCl was added to lime stone, It forms calcium chloride, water and carbon
dioxide gas.
(h) Pieces of blue vitriol were heated in a test tube. On cooling, water was added to it.
Answer:
When pieces of blue vitriol were heated in a test tube, the crystalline structure of blue vitriol broke down to form colourless powder and water evaporates. On cooling when water was added to colourless powder, blue vitriol regains its blue colour. All the above changes are physical changes.
(i) Dilute H2 SO4 was taken in an electrolytic cell and electric current was passed through it.
Answer:
When electric current was passed through dilute H2SO4 in an electrolytic cell,
H2 gas was formed at the cathode and O2 gas was formed at the anode.
3. Classify the following oxides into three types and name the types.
CaO,
MgO, CO2 , SO3 , Na2O, ZnO, Al2O3 , Fe2O3
Answer:
Basic
oxides: CaO, MgO, Fe2O3 ,
Acidic
oxides : CO2 , SO3, Na2O
Amphoteric
oxides: ZnO, Al2O3
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4. Explain by drawing a figure of the electronic configuration.
a.
Formation of sodium chloride from sodium and chlorine.
Answer: Sodium chloride:
1)An atom of sodium has one electron in its outermost orbit.
2)An atom of chlorine has seven electrons in its outermost orbit.
3)when these two atoms come close together, the sodium atom donates its electron and the chlorine atom accepts it, thus, both acquire octet state.
4) Due to this, the sodium ions respectively, this results in the formation of an ionic bond between the two ions, due to electrostatic force of attraction, giving rise to ionic compound sodium chloride.
b. Formation of magnesium chloride from magnesium and chlorine.
Answer:
Magnesium chloride
The
magnesium atom has 2 electrons in its outermost orbit. It gives electron from
its outermost orbit. It gives electrons from its outermost orbit and gets
converted into a positive ion with 2 unit positive charge.
The
chlorine atom has 7 electrons in its outermost orbit. So, each chlorine atom
needs o nly one electron to establish the octet state of its outermost orbit
and there by gets converted into a negatively charge.
So two
chlorine atoms accept one electron each from a magnesium atom and consequently
two chloride ion and a magnesium ion are formed.
Due to
the electrostatic force of attraction an ionic bond is formed and this results
in the formation of magnesium chloride molecule.
5. Show the dissociation of the following compounds on dissolving in water, with the help of chemical equation and write whether the proportion of dissociation is small or large.
Hydrochloric
acid, Sodium chloride, Potassium hydroxide, Ammonia, Acetic acid, Magnesium chloride,
Copper sulphate.
Answer:
6. Write down the concentration of each of the following solutions in g/L and mol/L.
a. 7.3g HCl in 100ml solution
b. 2g NaOH in 50ml solution
c. 3g CH3 COOH in 100ml solution
d. 4.9g
H2 SO4 in 200ml solution
{For complete Table Tilt (Rotate) Your Moibile }
|
Solute |
Quantity of solute |
Volume of solution |
Concentration of solution |
||||
|
A Name |
B Molecular formula |
C Molecular mass (u) |
D Gram (g) |
E = D/C Mole (mol) |
F Litre (L) |
G = D/F Gram/litre (g/L) |
H = E/F Molarity (Mol) |
|
Hydrochloric acid |
HCl |
36.5u |
7.3g |
0.2 mol |
100ml |
73 g/L |
2 mol/L |
|
Sodium hydroxide |
NaOH |
40u |
2g |
0.05 mol |
50ml |
40 g/L |
1 mol/L |
|
Acetic Acid |
CH3CooH |
60u |
3g |
0.05 mol |
50ml |
30 g/L |
0.5 mol/L |
|
Sulphuric
Acid |
H2SO4 |
98u |
4.9g |
0.05 mol |
200ml |
24.5 g/L |
0.25 mol/L |
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7. Answer the following questions.
a. Classify the acids according to their basicity and give one example of each type.
Answer:
Basicity of acids:
The number of H+ ions obtainable by the dissociation of one molecule of an acid is called its basicity.
Examples:
Monobasic acid : HCL, HNO3
Dibasic acid : H2SO4, H2CO3
Tribasic
Acid : H3BO3, H3PO4
b. What is meant by neutralization? Give two examples from everyday life of the neutralization reaction.
Answer:
An acid reacts with a base to form a salt and water is called the neutralization.
Examples from everyday life:
1)The person is suffering from acidity. The stomach of a person produces dilute acid which helps in digestion of food that he eats. When the production of acid is more than the required amount, the person suffers from acidity which causes burning sensation of the stomach. 2) In order to cure burning sensation of the stomach, people use basic substances called antacids. These antacids neutralize the excess acid in the stomach.
2)Before
we brush our teeth , The pH of saliva is less than 7 I.e acidic. Therefore,
neutralizes the acid produced in the mouth and prevent tooth decay.
c.
Explain what is meant by electrolysis of water. Write the electrode reactions
and explain them.
Answer:
8. Write the chemical equations for the following activities.
(a) NaOH solution was added to HCl solution.
Answer:
When NaOH solution was added to HCl solution, it forms sodium chloride and
water. It is a neutralization reaction.
(b) Zinc dust was added to dilute H2 SO4 .
Answer:
When zinc dust was added to dil. H2SO4. It forms zinc sulphate and hydrogen
gas.
(c) Dilute nitric acid was added to calcium oxide.
Answer:
(e)
Carbon dioxide gas was passed through KOH solution.
Answer:
When carbon dioxide gas was passed through KOH solution, it forms potassium
carbonate and water.
(f) Dilute HCl was poured on baking soda.
Answer: When dilute HCL was poured on baking soda, it forms sodium chloride and carbon dioxide gas.
9. State the differences.
Difference between Acids and bases
|
Acids |
Bases |
|
Acids
have sour taste. |
Bases
have bitter taste. |
|
Acids
have one or more H+ ions. |
Bases have one or more
OH- Ions. |
|
Acids
turn blue litmus red. |
Bases turn red litmus
blue |
|
Oxides
of non-metals form acids. |
Oxides of metals form bases. |
|
Ex:
HCl , H2SO4 |
Ex: NaOH, Ca(OH)2 |
b.
Difference between Cation and anion
|
Cation |
Anion |
|
1.Postitively
charged ions are called cations. |
1.Negatively charged
ions are called anions.
|
|
2.Cations
are attracted towards a cathode. |
2.Anions are attracted towards an anode.
|
|
.Usually
cations are obtained from metals and hydrogens |
3.Usually anions are
obtained from non-metals.
|
|
Ex.
Na+ , H+ |
4.Cl– , Br– , So42– |
Difference between Negative electrode and positive electrode.
|
Negative electrode |
Positive electrode |
|
1.
The negatively charged electrode is called a cathode. |
1.The positively
charged electrode called an anode. |
|
2.Cations
(positive ions) are attracted towards a cathode. |
2.Anions (negative ions) are attracted
towards an anode. |
|
3.Electrons
enter the solution at a cathode or a cathode supplies electrons. |
3.Electrons are
accepted by an anode. |
10. Classify aqueous solutions of the following substances according to their pH into three groups: 7, more than 7, less than 7.
Common
salt, sodium acetate, hydrochloric acid, carbon dioxide, potassium bromide,
calcium hydoxide, ammonium chloride, vinegar, sodium carbonate, ammonia,
sulphur dioxide
Answer:
|
pH |
Aquous solution of the substance |
|
7 |
Common salt |
|
Less
than 7 |
hydrochloric acid, carbon dioxide,
ammonium chloride, vinegar, sulphur dioxide |
|
More
than 7 |
sodium acetate,
potassium bromide, calcium hydoxide, sodium carbonate, ammonia. |
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