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Atoms and Molecules Viva Questions


ATOMS AND MOLECULES VIVA QUESTIONS (CLASS 9)

1. What is the Avogadro number of Helium (He) atoms weigh ?


Ans: 4.0 g


2. Determine the number of hydrogen atoms in 3 mole of NH3 ?


Ans: 9 x 6.02 x 1023


3. Which of the following weighs least among  the following?

(a) 0.224 litres of O2 at NTP

(b) 6.02 x 1023 molecules of oxygen

(c) 6.02 x 1023 atoms of carbon

(d) 10 g of CO2


Ans: 0.224 litres of O2 at NTP


4. An element's oxides contain 57.1 % and 72.1 % oxygen, respectively. What is the second oxide if the first oxide is MO?


Ans: MO2


5. What is the molarity of Na2CO3 solution containing 10.6 g per 500 ml solution?


Ans:  0.2


6. Determine the volume of 0.5 M HNO3 that can be prepared from 25 mL of 2.5 M HNO3


Ans: 125 mL


7. If 30 L is converted into SI unit and expressed in scientific notation,  determine the value obtained?


Ans:  3 x 10-2 m3


8. The average density of earth is 5.5 g cm-3. In kg m-3, determine the average density?


Ans: 5.5 x 10-3


9.  In 1.0046, how many significant figures are there?


Ans:  five


10. From the given lists, which of the following has more number of rnolecules ?

(a) 1 g CO2

(b) 1 g N2

(c) 1 g H2

(d) 1 g CH4


Ans: 1 g H2


11. Carbon monoxide and carbon dioxide may be taken as examples for illustrating which  law ?


Ans: Law of multiple proportions


12. From the given, which of the following contains Avogadro number of atoms,

(a) 11.2 L of H2 at STP

(b) 32 g of oxygen

(c) 28 g nitrogen

(d) 22.4 L of Cl2 at STP


Ans: 11.2 L of H2 at STP


13. Find the volume of oxygen at STP required to react with 3 g graphite to give CO2  ?


Ans: 5.6 L


14. A solute has a molecular mass of 60 g and 90 g of it is dissolved in a litre of solution. Then what is its molarity?


Ans: 1.5


15. From the given samples, determine which of the following is not a mixture?

(a) air (b) milk (c) smoke (d) water


Ans: Water


16. The volume of l g of a gas at STP is 1.12 L. What will be its molecular mass ?


Ans: 20


17. A mass of 16 g of an element was mixed with 32 g oxygen when 32 g of compound was formed. If the element was the limiting reagent, what will be the mass ratio of the element to oxygen in the compound ?


Ans:  1:1


18. Chemical equations are balanced so that they are in accordance with which law?


Ans: Law of conservation of mass


19. At NTP, 0.225 g of carbon reacts with 140 mL of oxygen. What would the compound's molecular formula be then?


Ans: C3O2


20. 0.25 g of a tetratomic element is 3.125 x 10-3 mole. Then what is the atomic mass of the element is


Ans:  20


21. Neon contains two isotopes of atomic masses 20 and 22 in the mass ratio 9 : 1  respectively. Find the atomic mass of the element ?


Ans: 20.2


22. What is the atomicity of ozone?


Ans: The atomicity of ozone is 2


23. Determine which molecule from the following elements is tetratomic?

(a) ozone (b) phosphorus (c) sulphur (d) xenon


Ans: Phosphorus


24. What is the number of significant figures in 6.023 x 1023 ?


Ans: The number of significant figures is  4  


25. Determine the approximate number of atoms present in lg CH3COOH ?


Ans:  The approximate number of atoms present is 1022


26. Find the number of significant figures in 0.0480 ?


Ans: The number of significant figures is 3


27. Give the number of dimensionally independent physical quantities in SI units?


Ans: 7


28. Give the equivalent of 1 cm3 of volume?


Ans: 10-3 dm3


29. Determine the equivalent of one joule of energy ?


Ans:  0.2381 cal


30. From the following, determine the SI unit of work?

(a) cal (b) Joule (c) litre-atm (d) ergs


Ans: Joule

 

31. One kg weight is equivalent to


Ans:  9.8 N


32. The unit of J. Pa-I is equivalent to


Ans:  m3


33.  From the listed elements, determine which of the element is not an element?

(a) Diamond (b) 22 carat gold (c) graphite (d) oxygen


Ans: 22 carat gold


34.  From the given mixtures, find which one is not a homogeneous mixture?

(a) one rupee coin (b) gasoline (c) iodised table salt (d) air


Ans: Iodised table salt


35.  Give the mass of a Mg atom ?


Ans: The mass of Mg atom is 24.3/6.02 x 1023 g  


36.  Determine the number of mols of carbon present in 1 mot of ethanol?


Ans:  2


37. 615.00 has...........significant figures


Ans: 5


38. How will you measure the Luminous intensity ?


Ans: The luminous intensity is measured in terms of Candela


39. The prefix tera means


Ans: 1012


40. Pure water can be obtained from sea water by which process?


Ans:  Distillation process


41. From the listed elements, find which one contains the largest number of molecules?

(a) 1g CO2  (b) 1g N2 (c) 1 g H2  (d) 1 g CH4    


Ans:  1 g H2   


42. Carbon forms two oxides CO and CO2. This illustrates which law?


Ans: Law of  Multiple proportions


43. Two oxides of a metal contain 50% and 60% of oxygen respectively. If the formula of the first oxide is MO, determine the formula of the second one?


Ans: The formula of the second one is M2O3


44. What is the simplest formula for a compound with 50% of element X (atomic mass 10) and 50% of element Y (atomic mass 20) in it?


Ans: The simplest formula is: X2Y


45. Which of the following contains the same number of atoms as in 6 g carbon?

(a) 24 g Mg  (b) 23 g Sodium  (c) 20 g Ca  (d) 63.5 g Cu


Ans: 20 g Ca 


46. 3.2 g of gas contains 6.02 x 1022 molecules. determine its vapour density?


Ans: The vapour density is 16


47. Find the volume of 1 M NaOH required to convert 1.2 g of NaHSO4 completely to Na2SO4 ?


Ans: 10 ml


48. How many moles of water would be formed when 4 g of methane (CH4) are burnt?


Ans: 0.5


49. calculate the number of significant figures of the following numbers?

(a) 100.04   

Ans: 5


(b) 4.20 x 1010 

Ans: 3


(c) 324.0

Ans: 4


(d) 500.00

Ans: 5


(e) 0.02670 

Ans: 4


50. Compute the following:

(a) 5.28 x 0.156 x 3/0.428

Ans: 5.77


(b) 5.28 x 0.156 x 3/0.421

Ans: 5.67


51.  List the proper number of significant figures in the following and indicate which zeros are significant?

(a) 0.216

Ans: 3 Significant figures


(b) 90.1

Ans: 3 Significant figures and zero is significant


(c) 800.0

Ans: 4 Significant figures all zeros are significant


(d) 0.0670

Ans: 3 Significant figures, last zero is significant


52.  Determine the number of moles of Oxygen atoms are there in

(a) one mole of HNO3

Ans: 3 moles


(b) one mole of H2SO4

Ans: 4 moles


53. Determine the number of moles of water produced when 8 g of methane (CH4) are burnt?


Ans: 1 mol.


54. How many moles of KClO3 are needed to give 1.5 moles of oxygen?


Ans: 1 mol.


55. How many moles of KCl are formed when 0.33 mol of KClO3 is decomposed?


Ans: 0.33 mol.


56. A chemist weighs 10 g of water, 10 g of ammonia and 10 g of hydrogen chloride. Calculate the total number of moles contained in the mixture?


Ans: 1.4 moles


57. Give the mass of a silver atom?


Ans: 1.794 x 10-22


58. Determine the number of molecules contained in a drop of water weighing 0.04 g?


Ans: 1.34 x 1021 molecules


59. Express 0.000000367 in scientific notation and calculate the significant figures?


Ans: 3.67 x 10-7 ; Number of significant figures is 3


60. What is the mass of HCl required to neutralise completely 5g  of NaOH?


Ans: 4.545 g


61. Which contains more molecules: 1 g of sulphur dioxide or 1 g of sulphur trioxide?


Ans: 1 g of SO2

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