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Board Paper of Class 10 2014 Chemistry - Solutions

General Instructions:
Answer 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 paper is the time allotted for writing the answers.

Section I is compulsory. Attempt any four questions from Section II.
The intended marks of questions or parts of questions are given in brackets [ ].



  • Question 1
     
    (a)  Choose the correct answer from the options given below:
    (i) Ionisation potential increases over a period from left to right because the
    A. Atomic radius increases and nuclear charge increases
    B. Atomic radius decreases and nuclear charge decreases
    C. Atomic radius increases and nuclear charge decreases
    D. Atomic radius decreases and nuclear charge increases
     
    (ii) A compound X consists of only molecules. Hence, X will have
    A. A crystalline hard structure
    B. A low melting point and low boiling point
    C. An ionic bond
    D. A strong force of attraction between its molecules
     
    (iii) When fused lead bromide is electrolysed, we observe
    A. A silver grey deposit at the anode and a reddish brown deposit at the cathode
    B. A silver grey deposit at the cathode and a reddish brown deposit at the anode
    C. A silver grey deposit at the cathode and reddish brown fumes at the anode
    D. Silver grey fumes at the anode and reddish brown fumes at the cathode
     
    (iv) The main ore used for the extraction of iron is
    A. Haematite
    B. Calamine
    C. Bauxite
    D. Cryolite

    (v) Heating an ore in a limited supply of air or in the absence of air at a temperature
    just below its melting point is known as
    A. Smelting
    B. Ore dressing
    C. Calcination
    D. Bessemerisation
     
    (vi) If an element A belongs to Period 3 and Group II, then it will have
    A. 3 shells and 2 valence electrons
    B. 2 shells and 3 valence electrons
    C. 3 shells and 3 valence electrons
    D. 2 shells and 2 valence electrons
     
    (vii) The molecule containing a triple covalent bond is
    A. Ammonia
    B. Methane
    C. Water
    D. Nitrogen

    (viii) The electrolyte used for electroplating an article with silver is
    A. Silver nitrate solution
    B. Silver cyanide solution
    C. Sodium argentocyanide solution
    D. Nickel sulphate solution
     
    (ix) Aluminium powder is used in thermite welding because
    A. It is a strong reducing agent.
    B. It is a strong oxidising agent.
    C. It is corrosion resistant.
    D. It is a good conductor of heat.
     
    (x) The IUPAC name of acetylene is
    A. Propane
    B. Propyne
    C. Ethene
    D. Ethyne
    		 [10]
    (b)  Fill in the blanks from the choices given within brackets: [5]
    (i) The basicity of acetic acid is-------- (3, 1, 4).  
    (ii) The compound formed when ethanol reacts with sodium is---------
    (sodium ethanoate, sodium ethoxide, sodium propanoate).
    (iii) Quicklime is not used to dry HCl gas because---------
    (CaO is alkaline, CaO is acidic, CaO is neutral).
      (iv) Ammonia gas is collected by---------- (an upward displacement of air, a downward displacement of water, a downward displacement of air).
      (v) Cold, dilute nitric acid reacts with copper to form---------
    (hydrogen, nitrogen dioxide, nitric oxide).
    (c) Give one word or phrase for the following: [5]
      (i) The ratio of the mass of a certain volume of gas to the mass of an equal volume of hydrogen under the same conditions of temperature and pressure  
      (ii) Formation of ions from molecules
      (iii) Electrolytic deposition of a superior metal on a baser metal
      (iv) Hydrocarbons containing a - C ||- functional group
      (v) The amount of energy released when an atom in the gaseous state accepts an
    electron to form an anion
    (d) Match the options A to E with the statements (i) to (v):
    A  Alkyne (i)  No. of molecules in 22.4 dm–3 of carbon dioxide at STP
    B Alkane (ii)  An element with electronic configuration 2, 8, 8, 3
    C Iron (iii)  CnH2n + 2
    D 6.023 × 1023 (iv)  CnH2n − 2
    E Metal (v)  The metal which forms two types of ions
    		[5]
    (e) Write balanced equations for the following:
    (i) Action of heat on a mixture of copper and concentrated nitric acid
    (ii) Action of warm water on magnesium nitride
    (iii) Action of concentrated sulphuric acid on carbon
    (iv) Action of dilute hydrochloric acid on sodium sulphide
    (v) Preparation of ethane from sodium propionate    		 [5]
    (f) Distinguish between the following pairs of compounds using the
    test given within brackets:
    (i) Iron (II) sulphate and iron (III) sulphate (using ammonium hydroxide)
    (ii) A lead salt and a zinc salt (using excess ammonium hydroxide)
    (iii) Sodium nitrate and sodium sulphite (using dilute sulphuric acid)
    (iv) Dilute sulphuric acid and dilute hydrochloric acid
     (using barium chloride solution)
    (v) Ethane and ethene (using alkaline potassium permanganate solution)    		 [5]
    (g) (i) Oxygen oxidises ethyne to carbon dioxide and water as shown by the equation:
    2C2H2 + 5O2 → 4CO2 + 2H2O
    What volume of ethyne gas at STP is required to produce 8.4 dm3 of
    carbon dioxide at STP? [H = 1, C = 12, O = 16]    		 [5]
      (ii) A compound made up of two elements X and Y has an empirical formula X2Y.
    If the atomic weight of X is 10 and that of Y is 5 and the compound ha a vapour
    density 25, find its molecular formula.
    VIEW SOLUTION


  • Question 2
    (a) State your observation in each of the following cases: [5]
      (i) When dilute hydrochloric acid is added to sodium carbonate crystals.  
      (ii) When excess sodium hydroxide is added to calcium nitrate solution.
      (iii) At the cathode, when acidified aqueous copper sulphate solution is electrolysed with copper electrodes.
      (iv) When calcium hydroxide is heated with ammonium chloride crystals.
      (v) When moist starch iodide paper is introduced into chlorine gas.
    (b) Study the figure given below and answer the questions which follow:
    		 [3]
    (i) Identify the gas Y.
    (ii) What property of gas Y does this experiment demonstrate?
    (iii) Name another gas which has the same property and can be demonstrated through this experiment.
    (c) (i) Name the other ion formed when ammonia dissolves in water. [2]
      (ii) Give one test which can be used to detect the presence of the ion produced.  
    VIEW SOLUTION


  • Question 3
    (a) State the conditions required for the following reactions to take place: [5]
      (i) Catalytic hydrogenation of ethyne
    (ii) Preparation of ethyne from ethylene dibromide
    (iii) Catalytic oxidation of ammonia to nitric oxide
    (iv) Any two conditions for the conversion of sulphur dioxide to sulphur trioxide
    (b) State the main components of the following alloys: [3]
    (i) Brass
    (ii) Duralumin
    (iii) Bronze
    (c) Give balanced equations for the following:  
      (i) Laboratory preparation of nitric acid [2]
      (ii) Preparation of ethanol from monochloroethane and aq. sodium hydroxide  
    VIEW SOLUTION


  • Question 4
    (a) Give the structural formula of the following: [4]
      (i) Ethanol
    (ii) 1-propanal
    (iii) Ethanoic acid
    (iv) 1, 2-dichloroethane
    (b) Draw the structure of the stable positive ion formed when an acid dissolves in water. [2]
    (c) State the inference drawn from the following observations:  
      (i) On carrying out the flame test with a salt P, a brick red flame was obtained. What is the cation in P? [4]
      (ii) A gas Q turns moist lead acetate paper silvery black. Identify the gas Q.  
      (iii) pH of liquid R is 10. What kind of substance is R?  
      (iv) Salt S is prepared by reacting dilute sulphuric acid with copper oxide. Identify S.  
    VIEW SOLUTION


  • Question 5
    (a)  Name the following: [3]
      (i) The property possessed by metals by which they can be beaten into sheets.
    (ii) A compound added to lower the fusion temperature of electrolytic bath in the extraction of aluminium.
    (iii) The ore of zinc containing its sulphide.
    (b)  Give one equation each to show the following properties of sulphuric acid: [3]
    (i) Dehydrating property
    (ii) Acidic nature
    (iii) As a non-volatile acid
     
    (c)  Give balanced chemical equations to prepare the following salts:  
      (i) Lead sulphate from lead carbonate [3]
      (ii) Sodium sulphate using dilute sulphuric acid  
      (iii) Copper chloride using copper carbonate  
    VIEW SOLUTION


  • Question 6
    (a) (i) State Avogadro's Law. [4]
    (ii) A cylinder contains 68 g of ammonia gas at STP.
    (a) What is the volume occupied by this gas?
    (b) How many moles of ammonia are present in the cylinder?
    (c) How many molecules of ammonia are present in the cylinder?
     [N = 14, H = 1]
    (b) (i) Why do covalent compounds exist as gases, liquids or soft solids? [3]
    (ii) Which electrode – anode or cathode – is the oxidising electrode? Why?
    (c) Name the kind of particles present in [3]
      (i) Sodium hydroxide solution  
      (ii) Carbonic acid  
      (iii) Sugar solution  
    VIEW SOLUTION


  • Question 7
    (a) An element Z has atomic number 16. Answer the following questions on Z:  
      (i) State the period and group to which Z belongs. [5]
    (ii) Is Z a metal or a non-metal?
      (iii) State the formula between Z and hydrogen  
      (iv) What kind of a compound is this?  
    (b) M is a metal above hydrogen in the activity series and its oxide has the formula M2O. This oxide when dissolved in water forms the corresponding hydroxide which is a good conductor of electricity. In the above context, answer the following: [5]
      (i) What kind of combination exists between M and O?
      (ii) How many electrons are there in the outermost shell of M?
      (iii) Name the group to which M belongs.
      (iv) State the reaction taking place at the cathode.
      (v) Name the product at the anode.
    VIEW SOLUTION
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