SCHOLASTIC APTITUDE TEST 2000

CHEMISTRY

Time: 1 Hour

Max.Marks : 60

Instructions:

(1) Answer must be written either in English or the medium of instruction of the candidate in high school.

(2) There will be no negative marking

(3) Use of calculators or graph papers is not permitted

(4) There are SIX Questions. Answer all the questions.

I. Differentiate the following: (10x2 =20 Marks)

  1. orbit - orbital
  2. rayon - nylon
  3. strong acid - concentrated acid
  4. polypeptides - polysaccharides
  5. periodicity - periodic properties
  6. acidity - basicity
  7. solution - colloid
  8. normal salt - acid salt
  9. vanderwaal’s forces - intermolecular forces
  10. hardening - annealing

II. Write the balanced Chemical Equations for following chemical changes:                 (5x1=5 Marks)

  1. Photographic film is exposed to sunlight.
  2. Lightening strucks the atmosphere.
  3. Burning magnesium ribbon is inserted into a jar of carbondioxide.
  4. Lime water is exposed to air.
  5. Red hot Iron interacts with steam.

III. Explain the following Facts: (10x2 = 20 Marks)

(Write the chemical equations wherever necessary)

  1. Formation of F-(g) from F(g) is exothermic where as formation of O2-(g) from O(g) is endothermic.
  2. Acetylene reacts with ammonical silver nitrate where as ethylene does not react with this reagent.
  3. HF is weaker than HCl is aqueous solution.
  4. In the electroplating of an article, the metal to be plated on the article is made as anode and article to be electroplated is placed at the cathode.
  5. Pure NaCl is precipitated when HCl is bubbled through concentrated solution of brine.
  6. MgSO4 crystallises with greater number of molecules of water of crystallisation than CaSO4.
  7. CO2 is gas where as SiO2 is solid at room temperature.
  8. Across a period from left to right atomic size should increase as the number of electrons is increasing. But atomic size decreases.
  9. K2Cr2O7 is used as oxidising agent in H2SO4 medium. Can we use HCl as acidic medium?
  10. An aqueous solution of I2 becomes colourless on adding little NaOH solution to it.

IV. Fill in the blanks: (5x1 = 5 Marks)

  1. The volume of steam produced when a mixture of 22.4 litres of Hydrogen and 22.4 litres of oxygen is ignited at 1000C ___________________.
  2. In nuclear reactions there is conservation of ______________ and ____________ for reactants and products.
  3. Half life periods of two bromine nuclei 80Br and 80Br are 4.4 hr and 18 minutes respectively. These two nuclei are called _____________.
  4. Aminoacids are water soluble and have high melting points due to ______________.
  5. Iron is independently converted into FeCl2 and FeCl3 by reacting with _________ and ____________ respectively.

V. Multiple choice. Each question has one or more answers. Indicate the correct answer by A,B,C,D. (5x1 = 5 Marks)

  1. Which of the following equilibria is (are) affected by pressure change
    A) N2+O2 Â 2NO B) N2+3H2 Â 2NH3
    C) 2O3 Â 3O2 D) H2+Cl2 Â 2HCl
  2. Atom X (with 1 valence electron), Atom Y (with 3 valence electrons) Atom Z (with 7 valence electrons) belong to same period in the periodic table. The correct formula(e) of compounds formed from these atoms are.
    A) YX3 B) ZX7 C) XZ D) YZ3
  3. If 92U235 undergoes decay only by emitting a and b particles, the possible product(s) of decay
    A) 89Ac227 B) 90Th227 C) 89Ac321 D) 91Pa231
  4. Auxochrome
    A) Is responsible for the colour of the dye
    B) forms chemical bonds between dye and fibre
    C) intensifies the colour of the dye
    D) all the above
  5. When a perfect gas is made to expand into vacuum at constant temperature
    A) its internal energy increases
    B) internal energy decreases
    C) decrease in internal energy is followed by its conversion is to liquid
    D) no change in internal energy

VI. Solve the following: (5 Marks)

  1. An experiment to measure Avogadro’s number involves the collection of a beam of alpha particles to which electrons are added to give neutral helium. Suppose that for a particular run it takes a number of electrons equivalent to 6.40x10-5 coulomb/sec to neutralise the beam, and that after 24 hours of collection 1.14x10-4 g of neutral helium are collected. From this data, determine Avogadro’s number. The charge on one electron is 1.602x10-19 coulombs. (24 hours is equivalent to 86,400 sec) 3M
  2. An element of atomic weight X consists of two isotopes of Mass number (X-1) and (X+2) what is the percentage abundance of heavier isotope. 2M