ICSE BOARD PAPER-2018-CHEMISTRY

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  • Q1

    (a)  Choose the correct answer from the options given below:

    (i)   The salt solution which does not react with ammonium hydroxide is:

    (A) Calcium Nitrate

    (B) Zinc Nitrate

    (C) Lead Nitrate

    (D) Copper Nitrate

     

    (ii)  The organic compound which undergoes substitution reaction is:

    (A) C2H2

    (B) C2H4

    (C) C10H18

    (D) C2H6

     

    (iii) The electrolysis of acidified water is an example of:

    (A) Reduction

    (B) Oxidation

    (C) Redox Reaction

    (D) Synthesis

     

    (iv)The IUPAC Name of dimethyl ether is:

    (A) Ethoxy methane

    (B) Methoxy methane

    (C) Methoxy ethane

    (D) Ethoxy ethane

     

    (v)  The catalyst used in the Contact Process is:

    (A) Copper

    (B) Iron

    (C) Vanadium pentoxide

    (D) Manganese dioxide

     

    (b)  Give one word or a phrase for the following statements:

    (i)   The energy released when an electron is added to a neutral gaseous isolated atom to form a negatively charged ion.

    (ii)  Process of formation of ions from molecules which are not in ionic state.

    (iii) The tendency of an element to form chains of identical atoms.

    (iv) The property by which certain hydrated salts, when left exposed to atmosphere, lose their water of crystallization and crumble into powder.

    (v)  The process by which sulphide ore is concentrated.

     

    (c)  Write a balanced chemical equation for each of the following:

    (i)   Action of concentrated sulphuric acid on carbon.

    (ii)  Reaction of sodium hydroxide solution with iron (III) chloride solution.

    (iii) Action of heat on aluminum hydroxide.

    (iv) Reaction of zinc with potassium hydroxide solution.

    (v)  Action of dilute hydrochloric acid on magnesium sulphite.

    (d) 

    (i)   Give the IUPAC name for each of the following:

     

    (ii)  Write the structural formula of the two isomers of butane.

     

    (e)  State one relevant observation for each of the following:

    (i) Lead nitrate solution is treated with sodium hydroxide solution drop wise till it is in excess.

    (ii) At the anode, when molten lead bromide is electrolyzed using graphite electrodes.

    (iii) Lead nitrate solution is mixed with dilute hydrochloric acid and heated.

    (ix) Anhydrous calcium chloride is exposed to air for some time.

    (x) Barium chloride solution is slowly added to sodium sulphate solution.

     

    (f)  Give a reason for each of the following:

    (i) Ionic compounds have a high melting point.

    (ii) Inert gases do not form ions.

    (iii) Ionisation potential increases across a period, from left to right.

    (ix) Alkali metals are good reducing agents.

    (x) Conductivity of dilute hydrochloric acid is greater than that of acetic acid.

     

    (g)  Name the gas that is produced in each of the following cases:

    (i)   Sulphur is oxidized by concentrated nitric acid.

    (ii)  Action of dilute hydrochloric acid on sodium sulphide.

    (iii) Action of cold and dilute nitric acid on copper.

    (iv) At the anode during the electrolysis of acidified water.

    (v)  Reaction of ethanol and sodium

     

    (h)  Fill up the blanks with the correct choice given in brackets.

    (i)   Ionic or electrovalent compounds do not conduct electricity in their ________state. (fused/solid)

    (ii)  Electrolysis of aqueous sodium chloride solution will form _______ at the cathode. (hydrogen gas/sodium metal)

    (iii) Dry hydrogen chloride gas can be collected by ________ displacement of air. (downward/upward)

    (iv) The most common ore of iron is ________. (calamine/haematite)

    (v)  The salt prepared by the method of direct combination is _______ (iron (II) chloride/ iron (III) chloride)     

     

    Marks:40
    Answer:

    (a)

    (i)

    (D) Copper Nitrate

    Explanation: Calcium nitrate, zinc nitrate and lead nitrate react with ammonium hydroxide to form respective hydroxide and ammonium nitrate solution.

     

    (ii)

    (D) C2H6

    Explanation: C2H6 is ethane. Ethane is a saturated hydrocarbon and this undergoes substitution reaction.

     

    (iii)

    (C) Redox Reaction

    Explanation: Electrolysis of acidified water is an example of redox reaction. During the electrolysis of acidified water, reduction takes place at the cathode and oxidation takes place at anode.

     

    (iv)

    (B) Methoxy methane

    Explanation: The structure of dimethyl ether is:

    CH3–O–CH3

    So, the IUPAC name of the compound is Methoxy methane

     

    (v)

    (C) Vanadium pentoxide

    Explanation: Sulphuric acid is produced in large amount

    in industries by Contact Process. The catalyst used for

    the process is vanadium pentoxide (V2O5).

     

     

    (b)

    (i) Electron affinity or electron gain enthalpy

    (ii) Ionization
    (iii) Catenation
    (iv) Efflorescence
    (v) Froth floatation

    (c)

    (d)

    (i)

    (i) Methanal

    (2) Propanol

    (3) But-2-ene

    (ii) CH3–CH2–CH2–CH3 (n-butane)

    (e)

    (i) Lead nitrate reacts with sodium hydroxide to form a white precipitate of lead (II) hydroxide and sodium nitrate.

    However, when excess of sodium hydroxide is added, it reacts with white precipitate of lead hydroxide to form a soluble salt of sodium plumbite.

     

    (ii) Reddish brown fumes of bromine evolve at the anode.

     

    (iii) White precipitate of lead chloride, PbCl2 is formed.

     

    (iv) Anhydrous calcium chloride on exposure to air absorbs moisture from the atmospheric air to become moist, and ultimately dissolves in absorbed water, forming a saturated solution.

    (v) On adding barium chloride to sodium sulphate solution, a white precipitate of barium sulphate is formed.

    (f)

    (i) The cations and anions in an ionic compound are held together by strong electrostatic force of attraction, so a large amount of energy is required to break the force of attraction between the ions. On account of this large requirement of energy, ionic compounds have high melting point.

     

    (ii) Inert gases have completely filled valence shell and thus are stable. So, they neither lose nor gain electrons to form ions.

     

    (iii) From left to right, in a Period, the atomic size decreases thereby increasing the effective nuclear change (the nuclear attraction on the electrons in the valence shell increases). Thus, more energy is required to pull out the electrons from the valence shell and hence ionisation potential increases.

     

    (iv) Alkali metals have only one electron in their valence shell. They readily lose this electron and attain stability. Hence, they are good reducing agents.

    (v) Hydrochloric acid is a strong acid that completely dissociates in water to give H+ and Cl ions while acetic acid is a weak acid and dissociates partially to in aqueous solution to give H+ and CH3COO ions. Thus, conductivity of dilute hydrochloric acid is greater than that of acetic acid.

     

    (g)

    (i) Nitrogen dioxide (NO2)

    (ii) Hydrogen sulphide (H2S)

    (iii) Nitric oxide (NO)

    (iv) Oxygen (O2)

    (v) Hydrogen (H2)

     

    (h)

    (i) solid

    (ii) hydrogen gas

    (iii) upward

    (iv) haematite

    (v) iron (III) chloride

    View Answer
  • Q2

    (a) 

    (i) What do you understand by a lone pair of electrons?

    (ii) Draw the electron dot diagram of Hydronium ion. (H = 1; O = 8)

     

    (b) 

    In Period 3 of the Periodic Table, element B is placed to the left of element A. On the basis of this information, choose the correct word from

    the brackets to complete the following statements:

    (i)   The element B would have (lower/higher) metallic character than A.

    (ii)  The element A would probably have (lesser/higher) electron affinity than B.

    (iii) The element A would have (greater/smaller) atomic size than B.

     

    (c)  Copy and complete the following table which refers to the conversion of ions to neutral particles.

          

    Conversion

    Ionic Equation

    Oxidation/Reduction

    Chloride ion to chlorine molecule

     

    (i)   _______

     

    (ii)  _________

     

    Lead (II) ion to lead

    (iii) _______

    (iv) _________

     

    Marks:10
    Answer:

    (a)

    (i) The unshared pair of electrons that do not take part in the bond formation is known as the lone pair of electrons.

    (ii) Hydronium ion [H3O+]

     

     

    (b)

    (i) Metallic character decreases on going from left to right in the Periodic Table therefore, the element B would have higher metallic character than A.

    (ii) Electron affinity increases on moving from left to right in a Periodic Table. Therefore, element A would probably have higher electron affinity than B.

    (iii) The atomic size decreases on moving from left to right in the Periodic Table. Therefore, the element A would have smaller atomic size than B.

     

    (c)

     

    Conversion

    Ionic Equation

    Oxidation/Reduction

    Chloride ion to chlorine molecule

     

    (i)2Cl Cl2 + 2e

     

    (ii)Oxidation

     

    Lead (II) ion to lead

    (iii)Pb2+ + 2e Pb

    (iv)Reduction

     

     

    View Answer
  • Q3

    (a) 

    (i) Write the balanced chemical equation to prepare ammonia gas in the laboratory by using an alkali.

    (ii) State why concentrated sulphuric acid is not used for drying ammonia gas.

    (iii) Why is ammonia gas not collected over water?

     

    (b)

    (i)  Name the acid used for the preparation of hydrogen chloride gas in the laboratory. Why is this particular acid preferred to other acids?

    (ii)  Write the balanced chemical equation for the laboratory preparation of hydrogen chloride gas.

     

     

    (c)  For the preparation of hydrochloric acid in the laboratory:
    (i)   Why is direct absorption of hydrogen chloride gas in water not feasible?
    (ii)  What arrangement is done to dissolve hydrogen chloride gas in water?

    (d)  For the electro-refining of copper:

    (i)   What is the cathode made up of?

    (ii)  Write the reaction that takes place at the anode.

    Marks:10
    Answer:

    (a)

    (i)

    (ii) Ammonia being basic in nature reacts with concentrated sulphuric acid to form ammonium sulphate. Therefore, concentrated sulphuric acid is not used for drying ammonia gas.

    (iii) Ammonia is highly soluble in water. Therefore, it cannot be collected over water.

     

    (b)

    (i) Sulphuric acid is used for the preparation of hydrogen chloride gas in the laboratory. It is non-volatile and may not volatilize out along with hydrogen chloride gas.

    (ii)

     

    (c)

    (i) Direct absorption of hydrogen chloride gas in water not feasible because this may lead to an explosion due to the heat produced when water comes in contact with hot concentrated sulphuric acid.

     

    (ii) Funnel arrangement is done to dissolve hydrogen chloride gas in water.

     

    (d)

    (i) Pure copper (Cu) metal

    (ii) Oxidation occurs at the anode which is as follows:

    Cu – 2e Cu2+

    View Answer
  • Q4

    (a)  The percentage composition of a gas is:

    Nitrogen 82.35%, Hydrogen 17.64%.

    Find the empirical formula of the gas. [N = 14, H = 1]

     

    (b)  Aluminum carbide reacts with water according to the following equation:

    Al4C3 + 12H2O → 4Al(OH)3 + 3CH4

    (i)   What mass of aluminum hydroxide is formed from 12g of aluminum carbide?

    (ii)  What volume of methane at s.t.p. is obtained from 12g of aluminum carbide?

    [Relative molecular weight of Al4C3 = 144; Al(OH)3 = 78]

     

    (c)

    (i)    If 150 cc of gas A contains X molecules, how many molecules of gas B will be present in 75 cc of B?

    The gases A and B are under the same conditions of temperature and pressure.

    (ii)  Name the law on which the above problem is based.

    (d)  Name the main component of the following alloys:

    (i)   Brass

    (ii)  Duralumin

    Marks:10
    Answer:

    (a)

    Given,

    Percentage of N = 82.35%,

    Percentage of H = 17.64%

    Atomic mass of N = 14

    Atomic mass of H = 1

     

    Element

    Percentage Mass

    Atomic Mass

    Number of atoms

    Simplest ratio

    N

    82.35

    14

    5.88

    5.88/5.88= 1

    H

    17.64

    1

    17.64

    17.64/5.88= 3

     

    Hence, the empirical formula of gas is NH3.

     

    (b)

    (c)

    (i)

    (ii) Avogadro’s Law

    (d)

    (i) Brass = Copper and Zinc

    (ii) Duralumin = Aluminium, Copper, Manganese and Magnesium

    View Answer
  • Q5

    (a)  Complete the following table which relates to the homologous series of hydrocarbons:

    General formula

    IUPAC name of the homologous series

    Characteristic bond type

    IUPAC name of the first member of the series

    CnH2n–2

    (A) _____

    (B) ______

    (C) ____

    CnH2n+2

    (D) ____

    (E) ______

    (F) ____

     

    (b)  

    (i) Name the most common ore of the metal aluminum from which the metal is extracted. Write the chemical formula of the ore.

    (ii)  Name the process by which impure ore of aluminum gets purified by using concentrated solution of an alkali.

    (iii) Write the equation for the formation of aluminum at the cathode during the electrolysis of alumina.

     

    Marks:10
    Answer:

    (a)

     

    General formula

    IUPAC name of the homologous series

    Characteristic bond type

    IUPAC name of the first member of the series

    CnH2n - 2

    (A) Alkynes

    (B) Triple bond (C C─)

    (C)Ethyne

    CnH2n + 2

    (D) Alkanes

    (E) Single bond

    (F) Methane

                 

    (b)

    (i) Most common ore of aluminium is bauxite. The chemical formula of bauxite is Al2O3.2H2O.

    (ii) Baeyer’s Process

    (iii) During the electrolysis of alumina, reaction that takes place at the cathode is:

    2Al3+ + 6e 2Al

    View Answer
  • Q6

    (a)  A compound X (having vinegar like smell) when treated with ethanol in the presence of the acid Z, gives a compound Y which has a fruity smell.

    (i)   Identify Y and Z.

    (ii)  Write the structural formula of X.

    (iii) Name the above reaction.

     

    (b)  Ethane burns in oxygen to form CO2 and H2O according to the equation:

    2C2H6 + 7O2 4CO2 + 6H2O

    If 1250 cc of oxygen is brunt with 300 cc of ethane.

    Calculate:

    (i)   The volume of CO2 formed.

    (ii)  The volume of unused O2.

    (c)  Three solutions P, Q and R have pH value of 3.5, 5.2 and 12.2 respectively.

    (i)   Weak acid?

    (ii)  Strong alkali?

    Marks:10
    Answer:

    (a)

    (i) Y is an ester, Ethyl ethanoate (CH3COOC2H5); and Z is concentrated sulphuric acid (H2SO4).

    (ii) X is ethanoic acid. Its structural formula is CH3COOH.

    (iii) The reaction is an esterification reaction.

     

    (b)

    (c)

    (i) Q having pH 5.2 is weak acid

    (ii) R having pH 12.2 is strong alkali.

    View Answer
  • Q7

    (a)  Give a chemical test to distinguish between the following pairs of chemicals:

    (i)   Lead nitrate solution and Zinc nitrate solution

    (ii)  Sodium chloride solution and Sodium nitrate solution

    (b)  Write a balanced equation for the preparation of each of the following salts:

    (i)   Copper sulphate from Copper carbonate.

    (ii)  Zinc carbonate from Zinc sulphate.

    (c)

    (i)  What is the type of salt formed when the reactants are heated at a suitable temperature for the preparation of Nitric acid?

    (ii)  State why for the preparation of Nitric acid, the complete apparatus is made up of glass.

    (d)  Which property of sulphuric acid is shown by the reaction of concentrated sulphuric acid with:

    (i)   Ethanol?

    (ii)  Carbon?

    Marks:10
    Answer:

    (a)
    (i) Lead nitrate and zinc nitrate can be distinguished by passing H2S in solution. Lead nitrate, Pb(NO3)2 on reaction with H2S forms a black precipitate of PbS while zinc nitrate, Zn(NO3)2 will not.

    (ii) Sodium chloride and sodium nitrate can be distinguished by silver nitrate test.

    Sodium chloride on reaction with silver nitrate forms a white precipitate of silver chloride, while sodium nitrate will not react with silver nitrate.

    (b)


    (c)

    (i) In the preparation of nitric acid, sodium or potassium nitrate reacts with sulphuric acid to form sodium bisulphate which is an acid salt.

    (ii) Nitric acid is prepared in a glass apparatus as nitric acid does not react with glass.

     

    (d)

    (i) Sulphuric acid acts as a dehydrating agent on reaction with ethanol.

    (ii) Sulphuric acid acts as an oxidising agent on reaction with carbon.

     

    View Answer