Solving ICSE Class 10 Chemistry Previous Year Question Papers ICSE Class 10 Chemistry Question Paper 2015 is the best way to boost your preparation for the board exams.
ICSE Class 10 Chemistry Question Paper 2015 Solved
Time: 2 hours
Maximum Marks: 80
General Instructions:
- Answers to this Paper must be written on the paper provided separately.
- You will not be allowed to write during the first 15 minutes.
- This time is to be spent in reading the Question Paper.
- The time given at the head of this paper is the time allowed for writing the answers.
- Section I is compulsory. Attempt any four questions from Section II.
- The intended marks for questions or parts of questions are given in brackets [ ].
Section – I (40 Marks)
(Attempt all questions from this Section)
Question 1.
(a) Select from the list the gas that matches the description given in each case: [ammonia, ethane, hydrogen chloride, hydrogen sulphide, ethyne]
(i) This gas is used as a reducing agent in reducing copper oxide to copper.
(ii) This gas produces dense white fumes with ammonia gas.
(iii) This gas is used for welding purposes.
(iv) This gas is also a saturated hydrocarbon.
(v) This gas has a characteristic rotten egg smell. [5|
Answer:
(i) Ammonia
(ii) Hydrogen chloride
(iii) Ethyne
(iv) Ethane
(v) Hydrogen sulphide
(b) Choose the most appropriate answer for each of the following:
(i) Among the elements given below, the element with the least electronegativity is:
(A) Lithium
(B) Carbon
(C) Boron
(D) Fluorine
Answer:
(A) Lithium
Lithium is an. element with the least electronegativity.
(ii) Identify the statement which does not describe the property of alkenes:
(A) They are unsaturated hydrocarbons
(B) They decolourise bromine water
(C) They can undergo addition as well as substitution reactions
(D) They undergo combustion with oxygen forming carbon dioxide and water.
Answer:
(C) They can undergo addition and substitution reactions.
Alkenes do not undergo substitution reaction.
(iii) This is not an alloy of copper:
(A) Brass
(B) Bronze
(C) Solder
(D) Duralumin.
Answer:
(C) Solder
Solder is an alloy of lead and tin.
(iv) Bonding in this molecule can be understood to involve coordinate bonding.
(A) Carbon tetrachloride
(B) Hydrogen
(C) Hydrogen chloride
(D) Ammonium chloride
Answer:
(D) Ammonium chloride
The bond formed between the nitrogen atom in ammonia and the chloride ion is a coordinate bond.
(v) Which of the following would weigh the least?
(A) 2 gram atoms of Nitrogen.
(B) 1 mole of Silver
(C) 22.4 litres of oxygen gas at 1 atmospheric pressure and 273K
(D) 6.02 . 1023 atoms of carbon.
[Atomic masses: Ag=108, N=14, 0=16, C=12] [5]
Answer:
(D) 6.02 . 1023 atoms of carbon.
(c) Complete the following calculations. Show working for complete credit:
(i) Calculate the mass of Calcium that will contain the same number of atom as are present in 3.2 gm of Sulphur. [Atomic masses: S=32, Ca=40] [2]
Answer:
32 g of sulphur contains 6.022 × 1023 atoms
1 g of sulphur contains = \(\frac{6.022 \times 10^{23}}{32 \mathrm{~g}}\) atoms
3.2 g of sulphur will contains = \(\frac{40}{6.022 \times 10^{23}}\) × 3.2 = 6.022 × 1022 atoms
6.022 × 1023 atoms of calcium will weigh 40 g
1 atom of calcium will weigh
= \(\frac{40}{6.022 \times 10^{23}}\) × 6.022 × 1022 = 4 g
(ii) If 6 litres of hydrogen and 4 litres of chlorine are mixed and exploded and if water is added to the gases formed, find the volume of the residual gas. [2]
Answer:
1 vol of Cl2 reacts with 1 vol of H2
4 litres of Cl2 reacts with 4 litres of H2
If water is added all hydrogen chloride will dissolve.
So volume of residual air = 2 litres of hydrogen.
(iii) If the empirical formula of a compound is CH and it has a vapour density of 13, find the molecular formula of the compound. [1]
Answer:
M.M. = 2 × V.D.
= 2 × 13
= 26
n = \(\frac{\text { Molecular mass }}{\text { Empirical mass }}\)
n = \(\frac{26}{13}\)
n = 2
Molecular formula = (CH)2 = C2H2.
(d) State one relevant observation for each of the following: [5]
(i) When crystals of copper nitrate are heated in a test tube.
Answer:
(ii) When the gaseous product obtained by dehydration of ethyl alcohol is passed through bromine water.
Answer:
(iii) When hydrogen sulphide gas is passed through lead acetate solution.
Answer:
(CH3COO)2Pb + H2S → 2CH3COOH + PbS (Black colouration appears)
(iv) When ammonia gas is burnt in an atmosphere of excess oxygen.
Answer:
4NH3 + 3O2 → 2N2 + 6H3O
Ammonia bums with a yellow flame.
(v) At the Anode when aqueous copper sulphate solution is electrolysed using copper electrodes.
Answer:
CuSO4 ⇌ Cu2+ + SO42-
At Anode:
Cu → Cu2+ + 2e–
Anode will be worn out and it will be reduced to a thin uneven strip.
(e) Identify the acid which matches the following description (i) to (v): [5]
(i) The acid which is used in the preparation of a non-volatile acid.
Answer:
Hydrochloric acid
(ii) The acid which produces sugar charcoal from sugar.
Answer:
Sulphuric acid
(iii) The acid which is prepared by catalytic oxidation of ammonia.
Answer:
Nitric acid
(iv) The acid on mixing with lead nitrate solution produces a white precipitate which is insoluble even on heating.
Answer:
Sulphuric acid
(v) The acid on mixing with silver nitrate solution produces a white precipitate which is soluble in excess ammonium hydroxide.
Answer:
Hydrochloric acid
(f) Give appropriate scientific reasons for the following statements: [5]
(i) Zinc oxide can be reduced to zinc by using carbon monoxide, but aluminium oxide cannot be reduced by a reducing agent
Answer:
Zinc oxide can be reduced to zinc by using carbon monoxide but aluminium oxide cannot be because of the following reasons:
(a) Aluminium oxide has a very high melting point.
(b) Aluminium has a high affinity for oxygen so it doesn’t lose its oxygen easily.
(ii) Carbon tetrachloride does not conduct electricity.
Answer:
Carbon tetrachloride has strong covalent bonding. It contains only molecules. Due to the absence of ions it is a bad conductor of electricity.
(iii) During electrolysis of molten lead bromide graphite anode is preferred to other electrodes.
Answer:
Graphite anode is preferred because bromine vapours do not react with graphite. On the other hand, even platinum electrodes are attacked by bromine vapours.
(iv) The electrical conductivity of acetic acid is less in comparison to the electrical conductivity of dilute sulphuric acid at a given concentration.
Answer:
Acetic acid is a weak acid, its degree of ionisation is very less whereas sulphuric acid is a strong acid, its degree of ionisation is very high. Thus, due to production of large number of ions sulphuric acid behaves as a strong acid and shows high electrical conductivity.
(v) Electrolysis is of molten lead bromide is considered to be a redox reaction.
Answer:
At Cathode : Pb2+ + 2e– → Pb(s) (Reduction)
At Anode : Br– – e– → Br
Br + Br → Br2 (Oxidation)
Since both reduction and oxidation occur in the same reaction, thus we can say that electrolysis of molten lead bromide is a redox reaction.
(g) (i) Give balanced chemical equations for the following conversions A, B and C: [3]
Answer:
(ii) Differentiate between the terms strong electrolyte and weak electrolyte. [2]
(stating any two differences)
Answer:
| Strong Electrolytes | Weak Electrolytes |
| They are almost completely dissociated in the molten or dissolved states. | They are only slightly dissociated in the molten or dissolved states. |
| They consist of free ions in the molten or dissolved states | They consist of molecules as well as ions in the molten or dissolved states. |
(h) Answer the following questions:
(i) Explain the bonding in methane molecule using electron dot structure. [2]
Answer:
Methane (CH<sub>4</sub>)
C(6) → 2, 4
H(1) → 1
(ii) The metal of Group 2 from top to bottom are Be, Mg, Ca, Sr, and Ba.
(1) Which one of these elements will form ions most readily and why?
(2) State the common feature in the electronic configuration of all these elements. [3]
Answer:
(1) Barium because its size is largest, effective nuclear charge is less and energy required to remove the outermost electron (Ionisation energy) is less.
(2) All these are alkaline earth metals with 2 valence electrons.
Section – II (40 Marks)
Attempt any four questions from this Section
Question 2.
(a) Arrange the following as per the instructions given in the brackets:
(i) Cs, Na, Li, K, Rb (increasing order of metallic character).
(ii) Mg, Cl, Na, S, Si (decreasing order of atomic size).
(iii) Na, K, Cl, S, Si (increasing order ionization energy)
(iv) Cl, F, Br, I (increasing order of electron affinity) [4]
Ans.
(i) Li < Na < K < Rb < Cs
(ii) Na > Mg > Si > S > Cl
(iii) K < Na < Si < S < Cl
(iv) I < Br < F < Cl
(b) Choose the most appropriate answer from the following list of oxides which fit the description. Each answer may be used only once:
[SO2, SiO2, Al2O3, MgO, CO, Na2O]
(i) A basic oxide.
(ii) An oxide which dissolves in water forming an acid.
(iii) An amphoteric oxide.
(iv) A covalent oxide of a metalloid.
Answer:
(i) Na2O
(ii) SO2
(iii) Al2O3
(iv) SiO2
(c) Element X is a metal with a valency 2, Y is 3 non-metal with a valency 3.
(i) Write an equation to show how Y from an ion.
(ii) If Y is a diatomic gas, write an equation for the direct combination of X and Y to from a compound. [2]
Answer:
X+2,y–
(i) Y + 3e– → Y-3.
(ii) 3X + Y2 → X3Y2
Question 3
(a) Give balanced chemical equations for the following conversions’.
(i) Ethanoic acid to ethyl ethanoate.
(ii) Calcium carbide to ethyne.
(iii) Sodium ethanoate to methane. [3]
Answer:
(b) Using theiil structural formulae identify the functional group by circling them:
(i) Dimethyl ether.
(ii) Propanone.
Answer:
(c) Name the following:
(i) Process by which ethane is obtained from ethene.
(ii) A hydrocarbon which contributes towards the greenhouse effect.
(iii) Distinctive reaction that takes place when ethanol is treated with acetic acid.
(iv) The property of element by virtue of which atoms of the element can link to each other in the form of a long chain or ring structure.
(v) Reaction when an alkyl halide is treated with alcoholic potassium hydroxide. [5]
Answer:
(i) Hydrogenation
(ii) Methane
(iii) Esterification reaction
(iv) Catenation
(v) Elimination reaction
Question 4.
(a) Identify the anion present in each of the following compounds:
(i) A salt M on treatment with concentrated sulphuric acid produces a gas which fumes in moist air and gives dense fumes with ammonia.
(ii) A salt D on treatment with dilute sulphuric acid produces a gas which turns lime water milky but has no effect on acidified potassium dichromate solution.
(iii) When barium chloride solution is added to salt solution E a white precipitate insoluble in dilute hydrochloric acid is obtained. [3]
Answer:
(a) (i) Chloride ion
NaCl + H2SO4 → NaHSO4 + HCl
HCl + NH3 → NH4Cl
(ii) Carbonate ion
Na2CO3 + H2SO4 → Na2SO4 + H2O + CO2↑
(iii) Sulphate ion
Na2SO4 + BaCl2 → 2NaCl + BaSO4
(b) The following table shows the tests a student performed on four different aqueous solutions which are X, Y, Z and W. Based on the observations provided, identify the cation present: [4]
| Chemical test | Observation | Conclusion |
| To solution X, ammonium hydroxide is added in minimum quantity first and then in excess. | A dirty white precipitate is formed which dissolves in excess to form a clear solution | (i) |
| To solution Y ammonium hydroxide is added in minimum quantity first and then in excess. | A pale blue precipitate is formed which dissolves in excess to form a clear inky blue solution. | (ii) |
| To solution W a small quantity of sodium hydroxide solution is added and then in excess. | A white precipitate is formed which remains insoluble. | (iii) |
| To a salt Z calcium hydroxide solution is added and then heated. | A pungent smelling gas turning moist red litmus paper blue is obtained. | (iv) |
Answer:
(i) Zinc
(ii) Copper
(iii) Magnesium
(iv) Ammonia
(c) Give balanced chemical equations for each of the following: [3]
(i) Lab preparation of ammonia using an ammonium salt
Answer:
(i)
(ii) Reaction of ammonia with excess chlorine.
Answer:
NH3 + 3Cl2 → NCl3 + 3HCl
(iii) Reaction of ammonia with sulphuric acid.
Answer:
2NH3 + H2SO4 → (NH4)2SO4
Question 5.
(a) Consider the following reaction and based on the reaction answer the questions that follow:
Calculate:
(i) the quantity in moles of (NH4)2Cr2O7 if 63gm of(NH4)2Cr2O7 is heated.
(ii) the quantity in moles of nitrogen formed.
(iii) the volume in litres or dm3 of N2 evolved at S.T.P.
(iv) the mass in grams of Cr2O3 formed at the same time.
(Atomic masses: H=1, Cr=52, N=14)
Answer:
(i) Wt. of (NH4)2Cr2O7
= (14 + 4) × 2 + 52 × 2 + 16 × 7
= 18 × 2 + 52 × 2 + 16 × 7
= 36 + 104 + 112 = 252
252 g represents 1 mole
1 g represents \(\frac{1}{252}\) mole
63 g represents \(\frac{1}{252}\) × 63 = \(\frac{1}{4}\) mole
= 0.25 mole
(ii) If 252 g of (NH4)2Cr2O7 is heated 1 mole of Nitrogen is formed.
1 g of (NH4)2Cr2O7 is heated mole of Nitrogen is formed.
63 g of (NH4)2Cr2O7 is heated \(\frac{1}{252}\) × 63 mole of Nitrogen is formed = 0.25 mole
(iii) 1 mole of compound is heated 22.4L of N2 is liberated.
0.25 mole of compound is heated 22.4 L × 0.25 of N2 is liberated = 5.6 L
(iv) M.M. of Cr2O3
= 2(52) + 3(16) = 104 + 48 = 152
252 g of (NH4)2Cr2O7 gives us 152 g of Cr2O3.
1 g of (NH4)2Cr2O7 gives us \(\frac{152}{252}\) g of Cr2O3.
63 g of (NH4)2Cr2O7 gives us × 63 g of Cr2O3 = 38 g of Cr2O3
(b) (i) For each of the substance listed below, describe the role played in the extraction of aluminium.
(1) Cryolite
(2) Sodium hydroxide
(3) Graphite [3]
(ii) Explain why :
(1) In the electrolysis of alumina using the Hall Heroult’s Process the electrolyte is covered with powdered coke.
(2) Iron sheets are coated with zinc during galvanization. |2]
Answer:
(i) (1) Cryolite: Cryolite is Na3AlF6. It acts as a solvent and lower the fusion temperature from 2050°C to 950°C.
(2) Sodium hydroxide: It increases the alkalinity of the mixture and helps to increase the conductivity of electrolyte.
(3) Graphite : Graphite is used as electrode during the extraction of aluminium.
(ii) (1) A layer of powdered coke is sprinkled over the surface of the electrolytic mixture. This reduces the heat loss by radiation and prevents carbon anode from burning in air (the point where carbon anodes emerges from the electrolyte).
(2) Iron sheets undergo rusting so in order to prevent iron from rusting, they are covered with zinc which is known as galvanization.
Question 6.
(a) (i) Give balanced chemical equations for the action of sulphuric acid on each of the following:
(1) Potassium hydrogen carbonate.
(2) Sulphur.
(ii) In the contact process for the manufacture of sulphuric acid give the equations for the conversion of sulphur trioxide to sulphuric acid. [2]
Answer:
(1) 2KHCO3 + H2SO4 → K2SO4 + 2H2O + 2CO2↑
(2) S + 2H2SO4 → 3SO2 + 2H2O
(ii)
SO3 + H2SO4 (cone.) → H2S2O7 (Oleum)
H2S2O7 + H2O → 2H2SO4 (sulphuric acid)
(b) (i) Copy and complete the following table: [2]
| Anode | Electrolyte | |
| Purification of copper |
(ii) Write the equation taking place at the anode. [1]
Answer:
(i)
| Anode | Electrolyte | |
| Purification of copper | Impure copper | Acidified CuSO4 |
(ii) at anode: Cu – 2e– → Cu2+
Impure copper anode loses electrons to form copper ions which move to solution.
(c) Explain the following:
(i) Dilute nitric acid is generally considered a typical acid but not so in its reaction with metals.
(ii) Concentrated nitric add appears yellow when it is left standing in a glass bottle.
(iii) An all glass apparatus is used in the laboratory preparation of nitric acid. [3]
Answer:
(i) All metals on reaction with acids liberate hydrogen gas but metals on reaction with nitric acid do not liberate hydrogen. Nitric acid being a strong oxidising agent oxidises hydrogen to water.
(ii) In the laboratory, the nitric acid stored in a bottle appears yellow, this is due to dissolved NO2 in the undecomposed HNO3. The colour of NO2 is brown but when it dissolves slightly it appears to be yellow.
(iii) All glass apparatus is used because nitric acid vapours are corrosive and may attack rubber cork or metal.
Question 7.
(a) The following questions are pertaining to the laboratory preparation of hydrogen chlo¬ride gas:
(i) Write the equation for its preparation mentioning the condition required. [1]
(ii) Name the drying agent used and justify your choice. [2]
(iii) State a safety precaution you would take during the preparation of hydrochloric acid. [1]
Answer:
(i)
(ii) The gas is purified and dried by passing through cone. H2SO4 which absorbs moisture.
We cannot use basic drying agents like calcium oxide (CaO) and phosphorus pentoxide (P2O5) because they react with it.
(iii) Use inverted funnel arrangement for its preparation. If inverted funnel arrangement is not used back suction can take place leading to cracking of all apparatus.
(b) An element L consists of molecules.
(i) What type of bonding is present in the particles that make up L?
(ii) When L is heated with iron metal, it forms a compound FeL. What chemical term would
you use to describe the change undergone by L? [2]
Answer:
(i) Covalent
(ii) L + Fe → FeL
Synthesis reaction
But as in FeL, it shows that iron has lost two electrons and L has accepted these two electrons. Thus, if we take this into consideration, then we can say L is an electronegative element with high electron affinity.
(c) From the list of the following salts choose the salt that most appropriately fits the description given in the following:
[AgCl, MgCl2, NaHSO4, PbCO3, ZnCO3, KNO3, Ca(NO3)2]
(i) A deliquescent salt.
(ii) An insoluble chloride.
(iii) On heating, this salt gives a yellow residue when hot and white when cold.
(iv) On heating this salt, a brown coloured gas is evolved. [4]
Answer:
(i) MgCl2
(ii) AgCl
(iii) ZnCO3
(iv) Ca(NO3)2