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Atoms And Molecules

Q. 1. What is law of conservation of mass ?

Q. 2. 100 g of 10% lead nitrate is mixed with 100 g of 10% sodium chloride solution in a closed container. 13.66 g of lead chloride is precipitated. The mixture contains 180 g of water and sodium nitrate. What amount of sodium nitrate is formed ?

Q. 3. State and explain law of constant proportion.

Q. 4. State and explain law of multiple proportions.

Q. 5. State the postulates of Dalton’s atomic theory of matter.

Q. 6. Explain the law of constant proportion on the basis of Dalton’s atomic theory.

Q. 7. Water and hydrogen are two compounds of hydrogen and oxygen. Which law of Dalton is confirmed by this observation ?

Q. 8. Write the drawbacks of Dalton’s atomic theory of matter.

Q. 9. What is one major drawback of Dalton’s atomic theory of matter ?

Q. 10. A sample of ammonia contains 28 g nitrogen and 6 g hydrogen. Another sample contains 15 g hydrogen. Find the amount of nitrogen in the second sample.

Q. 11. In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide , 0.9 g water and 8.2 g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass.

Q. 12. Hydrogen and oxygen combine in the ratio 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas ?

Q. 13. Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass ?

Q. 14. Which postulate of Dalton’s atomic theory can explain the law of definite proportions ?

Q. 15. Define atom and give examples of atom.

Q. 16.  What is the form of a atom that exists in a solid ?

Q. 17. How the names of elements were derived ?

Q. 18. Write the present accepted system of symbols of elements ?

Q. 19. State the term “symbols” of elements.

Q. 20. Give the significance of a symbol of an element with example.

Q. 21. What is the significance of Na, the symbol of sodium ?

Q. 22. Write the symbol of any five elements which is taken from their names in English.

Q. 23. Write the symbol of some elements which is taken from their names from a language other than English.

Q. 24. Write the symbol of following elements : Argon, Arsenic, Barium, Boron, Cesium, Chromium, Cobalt, Neon, Platinum, Silicon.

Q. 25. What is the contribution of Dalton’s atomic theory to the mass of atom ? How this issue were resolved ?

Q. 26. State and explain atomic mass of an element.

Q. 27. Define the atomic mass unit.

Q. 28.  How do atoms exists ?

Q.29. Why is it not possible to see an atom with naked eyes ?

Q. 30. What are molecules ? How are atoms arranged in the molecules ?

Q. 31.  Differentiate between a molecule and a compound.

Q. 32. “A molecule is the smallest particle of a substance (element or compound) having the properties of the substance and i s stable”. Comment.

Structure Of The Atoms

Q. 1. How can you say that matter is electrical in nature ?

Q. 2. Write about a discharge tube.

Q. 3. State the cathode rays. How are they produced ?

Q. 4. Give important properties of cathode rays.

Q. 5. Write the observation made, while conducting a discharge experiments, which showed that :

(i) Cathode rays travel in straight line.

(ii) Cathode rays are made up of material particles having mass and kinetic energy.

(iii) Cathode rays are negatively charged.

Q. 6. How will you explain the flow of current in a cathode ray experiment, knowing that gases are bad conductors of electricity ?

Q. 7. Relative atomic mass of an element A is 16.2.There are 2 isotopes with mass no.16 and 18 respectively of the element. Calculate the percentage of these 2 isotopes present in the element.?

Q. 9. State the properties of X-rays.

Q. 10. Define Isotopes. What are the characteristics of isotopes? Write any 4 uses of Isotope

Q. 11. Explain how X-rays are used to locate craks in fractured bones.

Q. 12. Give one use of X-rays giving the property which makes this use possible.

Q. 13. What is the mass and charge of an electron ?

Q. 14.Draw a diagram to show the presence of charge on cathode rays in the discharge tube and label it.

Q. 15. “Electrons are common constituents of all matter”. Comment.

Q. 16. How can you say that cathode rays are negatively charged particles ?

Q. 17. Experimentally show that cathode rays travel in straight line.

Q. 18. What are the limitations of Rutherford’s model of the atom?

Q. 19. Describe the different stages observed when a discharge tube is connected to a high voltage source and the pressure of the air in it is reduced gradually.

Q. 20. What happens when the cathode rays are passed through an electric field between two parallel plates ? What do you conclude with this experiment ?

Q. 21. State anode or positive rays. How are they produced ?

Q. 22.  State the important properties of anode rays.

Q. 23. State the observation that led to the conclusion that the nature of the anode rays depend upon the gas used in the cathode rays tube.

Q. 24. What can you say about the mass of the particles of anode rays ?

Q. 25. Explain how electricity is conducted through gases at very low pressures.

Q. 26. What is proton ? State its characteristics.

Q. 27. Differentiate between cathode rays and positive rays.

Q. 28. “All substances contain protons in addition to electrons”. Comment.

Q. 29. State the nature of charge on :

(i) X-rays    (ii) Cathode rays     (iii) Gamma rays     (iv) Anode rays.

Q. 30. State the differences in the discharge tube used to study cathode rays and the anode rays.

Q. 31. Name the fundamental particles discovered by

(i) Thomson   (ii) Goldstein    (iii) Chadwick.

Q. 32. ‘The mass and charge on positive rays change with change in nature of the gas in the discharge tube’. Give reason for this.  

Q. 33. State the significance of nature of protons found in the different elements.

Q. 34. What are canal rays ?

Q. 35. If an atom contains one electron and one proton, will it carry any charge or not ?

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