Posts Tagged ‘chemistry’

CBSE Class 12 Chemistry Test – Solid State

MM : 25 TIME : 40 MIN.
1. Give an example of ionic compound which show Frenkel defect.
2. What type of semiconductor is obtained when silicon is doped with Arsenic?
3. How do metallic and ionic substances differ in conducting electricity ?
4. How are the following properties of the crystals affected by Schottky and Frenkel defects
(i) Density (ii) Electrical Conductivity
5. What is the number of atom in a unit cell of
(i) face centered cubic structure
(ii) body centered cubic structure
6. What are F – centers ? Why are solids containing F – centers paramagnetic?
7. Account for the following :
(i) Fe3O4 is a ferromagnetic at room temperature but becomes paramagnetic at 850 K.
(ii) Zinc oxide on heating becomes yellow.
(iii) Frenkel defect does not change the density of AgCl crystal .
8. Chromium metal crystallizes in a body centered cubic lattice . The length of the unit cell edge is found to be 287 pm . Calculate the atomic radius of chromium
9. The density of Cu metal is 8.95 g cm-3. If the radius of Cu atom is 127.8 pm . Is the copper unit cell a simple cubic , a body centered or a face centered cubic structure ?
10. A cubic solid is made of two elements X and Y . Atoms Y are at corner of the cube and X at body centre . What is the formula of the compound ?
11. Calculate the distance between Na+ and Cl- ion in NaCl crystal if its density is 2.165 g cm-3 (Molar mass on NaCl = 58.5 g mol-1 )


Subscribe by Email

Be the first to comment - What do you think?  Posted by admin - February 21, 2013 at 1:14 pm

Categories: AISSCE CHEMISTRY, CBSE Chemistry, Chemistry Sample Papers   Tags: , , , , , , ,

CBSE Class 12 Chemistry Revision Test – Solutions

MM : 25                                             TIME : 40 MIN.
1. Two liquids A and B boil at 145oC respectively and 190oc respectively . Which of them has a higher vapour pressure at 80oc ?
2. Why is freezing point depression of 0.1 M sodium chloride solution nearly twice that of 0.1M glucose solution ?
3. Define the term molarity of the solution . State one disadvantage in using the molarity as the unit of concentration.
4. Define the term osmotic pressure . What is advantage of using osmotic pressure as compared to other colligative properties for the determination of molar masses of solutes in the solutions ?.
5. Non – ideal solutions exhibit either positive or negative deviation for Raoult’s law . What are these deviations and why are they caused ?
6. What mass of ethylene glycol (molar mass = 62g mol-1) must be added to 5.50 Kg of water to lower the freezing point of water to lower the freezing point of water from 00c to – 10 .0 0c ? [Kf for water = 1.86 K Kg mol-1 )
7. What concentration of nitrogen should be present in a glass of water at room temperature. Assume a temperature of 25oc a total pressure of 1 atmosphere and mole fraction of nitrogen in air of 0.78 (Kh for N2 = 8.42 x 10-7 M/mm Hg) .
8. The boiling point elevation of 0.30 g acetic acid in 100 g benzene is 0.0633 K . Calculate the molar mass of acetic acid from this data . What conclusion can you draw about the molecular state of the solute in the solution ? [Kb = 2.53 K Kg mol-1)
9. An antifreeze solution is prepared from 222.6 g of ethyleneglycol and 200 g of water . Calculate the molality of the solution . If density of this solution be 1.072gml-1 What will be the molarity of the solution?
10. Urea forms an ideal solution in water . Determine the vapour pressure of an aqueous solution containing 10% by mass of urea at 400c ( vapour pressure of water = 55.3 mm of Hg)
11. A 4% solution of sucrose is isotonic with 3% solution of an unknown organic substance . Calculate the molecular mass of unknown substance .


Be the first to comment - What do you think?  Posted by admin - at 1:12 pm

Categories: AISSCE CHEMISTRY, CBSE Chemistry, Chemistry Model Papers   Tags: , , , , , , ,

CBSE Class 12 Chemistry Question Bank – Solid State

CBSE Class 12 Chemistry Question Bank – Solid State

  1. What is a crystal?
  2. What are the different types of crystalline solids?
  3. Define a unit cell
  4. Why do atoms /ions in a crystal pack closely? Give two examples of close-packed structures.
  5. What are the coordination numbers for hcp and ccp structures?
  6. What do you understand by the term “ packing efficiency” ?
  7. What is radius ratio? What is its significance?
  8. Why do different ionic compounds assume different geometries of arrangement?
  9. What are the two type of holes or voids found in the close-packed structure of ionic compounds?
  10. What do you undersatand by defects in solids/
  11. What is the difference between a stoichiometric and a nonstoichiometric defect?
  12. What is a dopant? How does it affect the conductivity of a semiconductor?
  13. What are ferrimagnetic materials?
  14. Why do some solids exhibit magnetic properties?
  15. What type (n or p) of a semiconductor is created by the addition of arsenic to a crystal of germanium?
  16. Gallium arsenide can be made an n-type or p-type semiconductor by replacing some of the arsenic by another element.Which of the elements Se , Sb or Sn will work?
  17. Does the addition of Al2O3 to ZnO create an n-type or p-type semiconductor?
  18. Does doping ZnO with Li2O create an n-type or p-type semiconductor?

Be the first to comment - What do you think?  Posted by admin - February 18, 2013 at 5:22 pm

Categories: Question bank   Tags: , ,

Differences between acid and base and other questions

  1. List two difference between acid and base on  the basis of chemical properties
  2. Using the quation for electrolytic decomposition of water differentiate between a skeletal chemical equation and a balanced chemical equation
  3. State the change in colour name of the compound when iron material is exposed to air

Be the first to comment - What do you think?  Posted by admin - September 16, 2012 at 6:45 am

Categories: CBSE Chemistry   Tags: , , , , , , ,

What is a polymer?

Peter Barham describes the science of molecular chains.

Be the first to comment - What do you think?  Posted by admin - August 10, 2012 at 8:18 am

Categories: CBSE Chemistry   Tags: , , , , , , ,

« Previous PageNext Page »