Kerala Syllabus Class 9 Chemistry Model Question Paper Set 3 English Medium

Teachers recommend solving Kerala Syllabus 9th Standard Chemistry Question Papers Set 3 to improve time management during exams.

Kerala Syllabus Std 9 Chemistry Model Question Paper Set 3 English Medium

Score :40
Time: 1 1⁄2 hrs.

Instructions

• First 15 minutes is given as cool off time. This time is to be spent for reading and understanding the questions.
• Answer the questions according to the directions.
• Score and time to be considered while answering.

I. Answer any four questions from 1 – 5. Each carries 1 score. (4 × 1 = 4)

Question 1.
Which elements are called rare earths? (Lanthanoids, Actinoids, Halogens, Noble gases)
Answer:
J.J. Thomson

Question 2.
Who modified periodic law based on atomic number? (Linus Pauling, Mendeleev, Henry Moseley, Newton)
Answer:
Henry Moseley

Question 3.
Identify the relationship in the first pair and fill in the blanks in the second pair.
First group in the periodic table: Alkali metals
18th group in the periodic table: ________
Answer:
Noble gases

Question 4.
The chemical formula of nitric acid is ________
(H₂NO₃, H₃NO₃, HNO₃, H(NO₃)₂)
Answer:
HNO₃

Question 5.
Which of the following metal will react with hydrochloric acid and liberate hydrogen gas? (Copper, Silver, Gold, Zinc)
Answer:
Zinc

II. Answer any four questions from 6-10. Each carries 2 scores. (2 × 4 = 8)

Question 6.
a) How many elements are there in the second period of the periodic table?
b) Which is the noble gas in this period?
Answer:
a) Eight
b) Neon (Ne)

Question 7.
The electron configuration of certain elements is given in the table. (Symbols are not real).
A – 2,8,1
B – 2,8,7
C – 2,8,8,1
D – 2,8,8
a) Which of these belong to the same period?
b) Which of these belong to the same group?
Answer:
Same period – B and D
Same group – A and D

Question 8.
Match the following suitably

A	B
Neutron	J.J Thomson
Electron	Eugen Goldstein
Proton	Neils Bohr
Atom model	James Chadwick

Answer:

A	B
Neutron	James Chadwick
Electron	J.J Thomson
Proton	Eugen Goldstein
Atom model	Neils Bohr

Question 9.
Illustrate the formation of sodium chloride with an electron-dot structure.
(Hint: Atomic number Na: 11, Cl : 17)
Answer:

Question 10.
a) Which noble gas does not have an octet electron configuration?
b) Why is it stable even without a stable electron configuration?
Answer:
a) Helium (He)
b) Helium atom has only one shell in it. The maximum number of electrons that can be accommodated in the first shell is two. The helium has two electrons in the first shell. This duplet arrangement is stable.

III. Answer any four questions from 11 – 15. Each carries 3 scores.

Question 11.
a) Illustrate the chemical bonding in methane (CH₄) using symbols.
b) How many bondings are there in this molecule?
c) What is the nature of chemical bonding present in methane? (lonic bonding, Covalent bonding)
Answer:

b) Four
c) Covalent bonding

Question 12.
Shell model of an atom is illustrated below

a) Find out the atomic number and mass number of this atom.
b) Write the atomic number and electron configuration of the element on the right side of this element.
c) Write the shell atom model of the noble gas in the same period.
Answer:
a) Atomic number: 13
Mass number :13 + 14 = 27
b) Atomic number: 14
Electron configuration : 2,8,4

Question 13.
The Electronegativity values of three elements are given below
P = 3.44, Q = 1.31, R = 0.93
Find out whether the following compounds are ionic or covalent in nature.
Answer:
Electronegativity difference in PQ = 3.44 – 1.31 = 2.13
Since the difference is more than 1.7, the compound is ionic in nature.
Electronegativity difference in QR = 1.31 – 0.93 = 0.38.
Since it is less than 1.7, the compound is covalent in nature.

Question 14.
The symbols of certain elements are given below.

a) Find out a pair of isotopes from the above. Give reason.
b) Find out a pair of isobars from the above. What are isobars?
c) Write the use of any one isotope.
Answer:
a) Isotopes are \({ }_6^{14} \mathrm{D}\) and \({ }_6^{12} \mathrm{D}\)
Same atomic numbers and different mass numbers
b) Isobars are \({ }_20^{40} \mathrm{D}\)B and \({ }_18^{40} \mathrm{D}\)C
Isobars are atoms having the same mass number and different atomic numbers.
c) Carbon-14 isotope is used to find out the age of fossils.
U-235 isotope is used as a nuclear fuel.

Question 15.
Find out the statements related to J.J Thomson from those given below.
a) Conducted gold-foil experiment.
b) Put forward the plum pudding model of the atom.
c) Discovered electrons.
a) Put forward the planetary model of atom.
e) Conducted discharge tube experiments.
f) Proved the presence of protons in an atom.
Answer:
b) Put forward the plum pudding model of atom.
c) Discovered electrons.
e) Conducted discharge tube experiments.

IV. Answer any questions from 16-20. Each carries 4 scores. (4 × 4 = 16)

Question 16.
Classify the following statements as related to ionic compounds and covalent compounds.
a) Shows high melting and boiling points.
b) Dissolves in polar solvents like water.
c) Found in solid, liquid and gaseous states.
d) Dissolves in organic solvents like kerosene, benzene etc.
e) Shows low melting and boiling points.
f) Do not conduct electricity.
g) Found as crystalline solids.
h) Conduct electricity in molten state and in solutions.
Answer:
Related to ionic compounds
a) Shows high melting and boiling points.
b) Dissolves in polar solvents like water.
g) Found as crystalline solids.
h) Conduct electricity in molten state and in solution
Related to covalent compounds
c) Found in solid, liquid and gaseous states.
d) Dissolves in organic solvents like kerosene, benzene etc.
e) Shows low melting and boiling points.
f) Do not conduct electricity.

Question 17.
How does the size of an atom vary in periods and groups in the periodic table? Give reason.
Answer:
In periods from left to right, the size of atoms decreases. It is because from left to right nuclear charge increases. So, electrons are strongly attracted by the nucleus.
From top to bottom in a group, the size of atoms increases. This is because the number of shells increases from top to bottom in a group.

Question 18.
Suggest an experiment to prove the law of conservation of mass.
Answer:
Take 20 mL barium chloride solution in a beaker. Take 20 mL sodium sulphate solution in another beaker. Place both beakers in an electronic balance and note the reading. Then, pour the solution in one beaker into the other. Again note the reading. It can be seen that there is no change in the reading. This shows that mass of the reactants is equal to the mass of the products. This is law of conservation of mass.

Question 19.
Two chemical equations are given below.

a) Which of these is a redox reaction? Why?
b) Find out the oxidising agent, reducing agent, the atom gets oxidised and the atom gets reduced in these reactions.
Answer:

This is a redox reaction. Because both oxidation and reduction takes place simultaneously,

b) Oxidising agent =HCl
Reducing agent = Mg
Atom gets oxidised = Mg
(Because its oxidation number increases from zero to +2)
Atom gets reduced = H
(Because its oxidation number decreases from +1 to zero)

Question 20.
Symbols of certain cations and anions are given in the table below. Write the chemical formula of any four compounds formed by them.

Cations	Anions
Ca2+	\(\mathrm{NH}_3{ }^{-}\)
K+	\(\mathrm{NH}_4{ }^{3-}\)
\(\mathrm{NH}_4{ }^{+}\)	\(\mathrm{SO}_4{ }^{2-}\)

Answer:
Ca(NO₃)₂ – Calcium nitrate
Ca₃(PO₄)₂ – Calcium phosphate
CaSO₄ – Calcium sulphate
KNO₃ – Potassium nitrate
K₃PO₄ – Potassium phosphate
K₂SO₄ – Potassium sulphate
NH₄NO₃ – Ammonium nitrate
(NH₄)₃PO₄ – Ammonium phosphate
(NH₄)₂SO₄ – Ammonium sulphate