ICSE Class 9 Chemistry Sample Question Paper 3 with Answers

ICSE Class 9 Chemistry Sample Question Paper 3 with Answers

Section -1
(Attempt all questions from this Section)

Question 1.
(a) Fill in the blanks with the correct choice given in brackets.
(i) The number of shells is equal to the number of …………….. [valence electrons/protons]
(ii) Mendeleev’s periodic table contains vertical columns called …………… [groups/periods]
(iii) The chemical reaction that takes place in the presence of light are known as …………….. [photolysis/endothermic]
(iv) The molecular formula of baking soda is ………….. [NaHCO₃/CaCO₃]
(v) …………… pollution is the effect of undersirable changes in our surroundings that have harmful effects on plants, animals and human beings. [Sound/Environmental]
Answer:
(i) Valence electrons
(ii) Groups
(iii) Photolysis
(iv) NaHCO₃
(v) Environmental.

(b) Choose the correct answer from the options given below :
(i) The following causes nausea and irritation in the eyes and the throat.
(A) Hydrogen sulphide
(B) Oxygen
(C) Carbon monoxide
(D) Nitrogen oxide
Answer:
(A) Hydrogen suiphide

(ii) How many horizontal rows are there in the modem periodic table ?
(A) 7
(B) 5
(C) 8
(D) 10
Answer:
(A) 7

(iii) A solution may be formed by mixing :
(A) A liquid with a gas
(B) A solid with a liquid
(C) A liquid with another liquid
(D) All of the above
Answer:
(D) All of the above

(iv) The S. I. unit of pressure is :
(A) Joule
(B) Doctor
(C) Pascal
(D) Celsius
Answer:
(C) Pascal

(v) The temperature of 0° Kelvin on the Celsius scale is equal to :
(A) – 273 C
(B) + 273 C
(C) 0 C
(D) 100 C
Answer:
(A) – 273C

(c) Name the following :
(i) An oxidising agent which does not contain oxygen.
(ii) A substance which oxidises concentrated HCl to chlorine.
(iii) A substance which will reduce aqueous iron (III) ions to iron (II) ions.
(iv) A liquid which is an oxidising agent as well as a reducing agent.
(v) A solid which is an oxidising agent.
Answer:
(i) Cl (Chlorine)
(ii) MnO₂ (Manganese oxide)
(iii) H₂S (Hydrogen sulphide)
(iv) H₂O₂ (Hydrogen peroxide)
(v) MnO₂ (Manganese oxide)

(d) Give a reason for each of the following :
(i) Why the three elements chlorine (35.5), bromine (80) and iodine (127) form a triad?
(ii) Why hydrogen belongs to the first group and the first period of the periodic table?
(iii) Why hydrogen-oxygen mixture is called detonating mixture?
(iv) Why washing soda, when exposed to air becomes a monohydrate?
(v) Why noble gases are called chemically inactive gases?
Answer:
(i) 1. All are non-metals.
2. All of them reacts with water to form acids.
3. All have valency 1.

(ii) Hydrogen in the first element in the periodic table. Its atomic number is 1, and it has only 1 electron in its valence shell. Therefore, it belongs to the first group in the first period of the periodic table.

(iii) Hydrogen is a highly reactive fuel. When hydrogen molecules react with oxygen, new molecular bonds are formed which results in an explosive release of energy and the production of water.

(iv) Washing soda, when exposed to air becomes a monohydrate because it loses its water of crystallisation on exposure to air.
\(\mathrm{Na}_{2} \mathrm{CO}_{3} \cdot 10 \mathrm{H}_{2} \mathrm{O} \stackrel{\text { Dry air }}{\longrightarrow} \mathrm{Na}_{2} \mathrm{CO}_{3} \cdot \mathrm{H}_{2} \mathrm{O}+9 \mathrm{H}_{2} \mathrm{O}\)
(v) Noble gases are called chemically inactive gases because they have 8 electrons in their outermost shell, so they cannot gain or lose electrons. Therefore, they are chemi¬cally inactive.

(e) What do you observe when :
(i) When dilute sulphuric acid is added to given unknown substance.
(ii) When ammonium dichromate is heated.
(iii) When white crystalline solid is heated.
(iv) When mercuric oxide is heated.
(v) When iron pieces are dropped into a blue coloured copper sulphate solution.
Answer:
(i) A colourless gas with a foul smell, as of rotten eggs is evolved. Gas evolved is hydrogen sulphide.
(ii) The orange colour of -the substance changes to green colour and water vapour and nitrogen gas are produced.
(iii) It sublimates to form a basic NH₂ gas and an acidic gas (HCl).
(iv) It decomposes to form two elements one is mercury and the other is oxygen.
(v) The blue colour of the solution fades and turns into light green due to formation of ferrous sulphate.

(f) (i) What is gas ?
(ii) What is absolute zero temperature ?
(iii) What is standard temperature and pressure ?
Answer:
(i) The state of matter in which inter-particle attraction is weak and inter-particle space is so large that the particles become completely free to move randomly in the entire available space is known as gas.

(ii) The temperature at which the molecular motion completely ceases (theoretical concept), on the Kelvin scale is absolute zero.

(iii) The standard temperature (T) of a gas is defined as the degree of hotness of that gas. Whereas the standard pressure (P) of a gas is the force that the gas exerts per unit area on the walls of its container.

(g)(i) Balance each of the chemical equations given below :
1. Cu + H₂SO₄ → CuSO₄ + SO₂ + H₂O
2. KCl → K + Cl₂

(ii) Identify the substance which matches the description given below :
1. Which turns lime water milky ?
2. Which results in the formation of sodium carbonate on heating ?
3. Which when heated sublimates to form violet vapours ?

(h) Match Column A with Column B.

	Column A	Column B
(i)	Blue salt changes to white and then black.	(A) Ammonium dichromate
(ii)	Orange coloured compound changes to green.	(B) Iodine
(iii)	Red coloured compound changes to Brown and then yellow.	(C) Zinc nitrate
(iv)	White to yellow when hot and white when cold.	(D) Copper sulphate
(v)	Violet solid changes to violet vapours.	(E) Red lead

Section – II
(Attempt any four questions from this section)

Question 2.
(a) The formula of the chloride of a metal ‘M¹ is MO₂. State the formula of its :
(i) Nitrogen
(ii) Hydrogen
(iii) Carbon
Answer:
(i) Nitrogen dioxide
(ii) Hydrogen peroxide
(iii) Carbon dioxide

(b) Write balanced chemical equations for each of the following :
(i) Preparation of ammonia by ammonium chloride and calcium hydroxide.
(ii) When potassium dichromate reacts with hydrochloric acid.
(iii) Reaction of iron with water.
Answer:
(i) 2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2NH₃ + 2H₂O 2KCl
(ii) K₂Cr₂O₇ + 14HCl → 2KCl+ 2CrCl₃ + 7H₂Q + 3Cl₂
(iii) 2Fe + 3H₂O → Fe₂O₃ + 3H₂

(c) Draw the orbit structure for each of the following compounds :
(i) Sodium chloride [Na = 11 and Cl = 17]
(ii) Magnesium
(iii) Oxygen
(iv) Argon
Answer:

Question 3.
(a) (i) Name the industrial method for the production of hydrogen gas.
(ii) Name the promoter used in the above process.
(iii) Write one test for hydrogen.
Answer:
(i) Bosch process is the name of the industrial method for the production of hydrogen gas.
(ii) Chromic oxide (Cr₂O₃) acts as a promoter in Bosch process.
(iii) Hydrogen bums silently in air or oxygen with a pale blue flame, forming water.
2H₂ + O₂ → 2H₂O

(b) (i) What is periodic table ?
(ii) Why periodic table is called periodic table ?
(iii) What is the reason for discarding the law of triad ?
Answer:
(i) Periodic table is a chart of elements prepared in such a way that elements with similar
properties occur in same vertical column or group.
(ii) It is called periodic because elements with similar properties occur at fixed intervals or periods and it is called a table because elements are arranged in tabular forms.
(iii) 1. Dobereiner failed to arrange all the then known elements in a triad.
2. The law did not fully apply even within the same family.
(c) The d-block elements are known as transition elements. They are included in groups 3 to 12.

(c) What are transition elements ? Give examples and also write their main characteristics :
Answer:
The d-block elements are known as transition elements. They are included in groups 3 to 12.
Their main characteristics are as follows :
1. All these elements are metals with high melting and boiling points.
2. They are good conductors of heat and electricity.
3. Most of these elements are used as catalysts.
4. Some of these elements are attracted towards a magnet.
5. Most of these elements exhibit variable valencies.
6. Most of these elements form coloured ions and coloured compounds.
Some of the d-block elements are : Scandium, Titanium, Iron and Cobalt etc.

Question 4.
(a) At what temperature will 500 cm³ of a gas measured at 20°C occupy half its volume ? The pressure is kept constant.
Answer:

(b) The volume of a given mass of a gas with some pieces of marble in a container at 760 mm Hg pressure is 100 ml. If the pressure is changed to 1000 mm Hg, the new volume is 80 ml. Find the volume occupied by the marble pieces, if the temperature remains constant.
Answer:
Let the volume occupied by the marble pieces = V ml.
At 760 mm Hg, the volume occupied by the gas = (100 – V)
At 1000 mm Hg, the volume occupied by the gas = (80 – V)
By Boyle’s law,  P₁V₁ = P₂V₂760 x (100 – V) – 1000 x (80 – V)
Or 24 V = 400 ml
Or  V = 16.6 ml
The required volume = 16.6 ml.

(c) Calculate the relative molecular mass of each of the following :
(i) Ammonium dichromate [(NH₄)₂Cr₂O₇]
(ii) Methane (CH₄)
Answer:
(i) Molecular masses of the elements :Nitrogen : 14.007 g/mol
Hydrogen : 1.00794 g/mol
Chromium : 51.9961 g/mol
Oxygen : 15.999 g/mol
Molecular mass of ammonium dichromate
= (2 x 14.007) + (8 x 1.00794) + (2 x 51.9961) + (7 x 15.999) = 252.06 g/mol

(ii) Atomic mass of carbon = 12.011
Atomic mass of hydrogen = 1.00794
Molecular mass = 12.011 + (1.00794 x 4)
Molecular mass of methane = 16.04276 g/mol

Question 5.
(a) (i) Describe the “plum pudding” model of the atom ?
(ii) Compare Dalton’s atomic theory with the modem atomic theory.
Answer:
(a) (i) After the discovery of electrons and protons J. J Thomson proposed “plum pudding” model of the atom. According to this model :
1. An atom is considered to be a sphere of uniform positive charge and electrons are embedded into it.
2. The total positive charge is equal to the total negative charge so that an atom as a whole is electrically neutral.
3. The mass of an atom is considered to be uniformly distributed

Dalton’s atomic theory	Modem atomic theory
Atoms are indivisible particles.	Atoms are divisible into sub-atomic particles like protons, electrons and neutrons.
Atoms can neither be created nor be destroyed.	Atoms can be created and destroyed by nuclear fission and fusion.
Atoms follow the law of chemical combination to form compounds.	In the formation of organic compounds, the laws of chemical combination are not always followed.

(b) State the type of covalent bonding in the following molecules :
(i) Ethyne
(ii) Ammonia
(iii) Oxygen
Answer:
(i) Triple covalent bond is present in ethyne.
(ii) Single covalent bond is present in ammonia.
(iii) Double covalent bond is present in oxygen.

(c) How would you distinguish between the following pairs of substances on the basis of the tests given in brackets ?
(i) Sodium chloride and potassium chloride (flame test)
(ii) Zinc and sodium sulphite (action of dilute sulphuric acid)
Answer:
(i) When flame test is performed on the above given substances the following
observations are made :

(ii) When dilute sulphuric acid is passed through the zinc and then it is warmed, vigorous effervescence occurs and a colourless, odourless gas evolves.
Zn + H₂SO₄ → ZnSO₄ + H₂
When dilute sulphuric acid is passed to the (Sodium sulphite) and then it is warmed, a colourless gas with suffocating smell of burning sulphur is evolved.
Na₂SO₃ + H₂SO₄ → Na₂SO₄ + H₂O + SO₂

Question 6.
(a) Explain why water is called as “Universal solvent” ?
(b) Write the importance of air dissolved in water.
(c) Write two types of chemical reactions with examples of each.
Answer:
(a) Water is remarkable solvent. It dissolves many substances, forming aqueous solutions. Water has a high dielectric constant. As a result, it reduces the electrostatic force of attraction between positive and negative ions and dissolves even inorganic compounds, which are usually electrovalent. Not only solids, but also gases and other liquids dissolve in water. Hence, it is difficult to find absolutely pure water in nature. For the same reason, water is called a universal solvent.

(b) Air dissolved in water is biologically important.
1. Marine life, like fish, use the oxygen of the air dissolved in water for respiration and thus aquatic life is sustained.
2. Aquatic plants make use of dissolved carbon dioxide for photosynthesis e., to prepare their food.
3. Carbon dioxide dissolved in water reacts with limestone to form calcium bicarbonate. Marine organisms such as snails, oysters, etc., extract calcium carbonate from calcium bicarbonate to build their shells.

(c) Types of chemical reactions :
1. Direct combination reactions : A reaction in which two or more substances combine to form a single substance is called a combination reaction.
A + B → AB
Example : Photosynthesis reaction
The reaction of photosynthesis is also a combination reaction, which is endothermic. It takes place in the presence of sunlight where small molecules of carbon dioxide and water are used to make glucose.
\(6 \mathrm{CO}_{2}+6 \mathrm{H}_{2} \mathrm{O} \stackrel{\text { Sunlight and chlorophyll }}{\longrightarrow} \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+6 \mathrm{O}_{2}\)
The green pigment chlorophyll is essential for this reaction, because it traps energy from the sun.

2. Decomposition reaction : It is the breaking up of a compound either into elements or simpler compounds, such that these products do not recombine to form the original compound. A decomposition reaction that is brought about by heat is known as thermal decomposition.
Example : The compound mercuric oxide, when heated decomposes to form two elements, mercury and oxygen.
2HgO(s) → 2Hg(l) + O₂

Question 7.
(a) Complete the following table :

(b) If K and L shells of an atom are full, then what would be the number of electrons in the atom?
(c) From the symbol \(\frac{31}{15} \mathrm{P}\) state.
(i) Electronic configuration of phosphorus
(ii) Mass number of phosphorus.
Answer:
(a) (i) Atomic number = Number of electrons = Number of Protons = 1 Mass number = Number of protons + Number of neutrons
= 11 + 12 = 23

(ii) Atomic number = Number of electrons = Number of Protons
= 16

S. No.	Element	Mass Number	Atomic Number	Number of Electrons	Number of Protons	Number of Neutrons
(i)	Sodium	23	11	12	11	12
(ii)	Sulphur	32	16	16	16	16

(b) Maximum number of electrons in K shell = 2 Maximum number of electrons in L shell = 8
If an atom has completely filled shells, then it has 2 and 8 electrons in K and L shell respectively.
Hence, total number of electrons in the atom = 2 + 8 = 010.

(c) (i) 2,8,5 (ii) 31

ICSE Class 9 Chemistry Question Papers with Answers