Mole Concept | Some Basic Concepts of Chemistry MCQs and Answers with FREE PDF

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1. Mass of one atom of the element A is 3.985410-23. How many atoms are contained in 1 gm of the element A?

(a)    2.509 1023

(b)    6.022 1023

(c)    12.044 1023

(d)     None of these

2. Density of a 2.05 M solution of acetic acid in water is 1.02 g/mL. The molality of the solution is:

(a)    1.14 mol kg–1

(b)    3.28 mol kg–1

(c)    2.28 mol kg–1

(d)    0.44 mol kg–1

3. If water sample are taken from sea, rivers or lake, they will be found to contain hydrogen and oxygen in the approximate ratio of 1 : 8.This indicates the law of :     

(a) Multiple proportion

(b) Definite proportion

(c) Reciprocal proportions

(d) None of these

4. Hydrogen and oxygen combine to form H2O2 and H2O containing 5.93% and 11.2 % hydrogen respectively. The data illustrates :

(a) Law of conservation of mass

(b) Law of constant proportion

(c) Law of reciprocal proportion

(d) Law of multiple proportion

5. Total number of moles oxygen atoms in 3 litre O3 (g) at 270C and 8.21 atm are:

(a) 3

(b) 1

(c) 1

(d) None of these

6. One atoms of an element x weigh 6.64310-23 g. Number of moles in 20 kg is :

(a) 4

(b) 40

(c) 100

(d) 500

7.  Which of the following contains the largest mass of hydrogen atoms?

(a) 5.0 moles C2H2O4

(b) 1.1 moles C3H8O3

(c) 1.5 moles C6H8O6

(d) 4.0 moles C2H4O2

8. It is known that atom contain protons, neutrons and electrons. If the mass of neutron assumed to half of its original value whereas that of proton is assumed to be twice its of original value then the atomic mass of will be :

(a) Same

(b) 14.28 % less

(c) 14.28 % more

(d) 28.56 % less    20.

9. Mass of 1 atom of hydrogen

(a)    1.66 ´ 10–28 g

(b)    1.66 ´ 10–27 g

(c)    1.66 ´ 10–24 g

(d)    1 g

10. The dot at the end of this sentence has a mass of about one microgram. Assuming that the black stuff is carbon, number of atoms of carbon needed to make such a dot is approximately

(a)    5 ´ 1012 atoms

(b)    5 ´ 1014 atoms

(c)    5 ´ 1016 atoms

(d)    5 ´ 1018 atoms

11. The mass of 1 ´ 1022 molecules CuSO4 5H2O is

(a)    41.59 g

(b)    415.9 g

(c)    4.159 g

(d)    None of these

12. If 1021 molecules are removed from 200 mg of CO2, then the number of moles of CO2 left are

(a)    2.88 ´ 10–3

(b)    1.66 ´ 10–3

(c)    4.54 ´ 10–3

(d)    1.66 ´ 10–2

13. How many molecules are present in one gram of hydrogen?

(a)    6.02 ´ 1023

(b)    3.01 ´ 1023

(c)    2.5 ´ 1023

(d)    1.5 ´ 1023

14.  The mass percentage of oxygen in NaOH is

(a)    40

(b)    60

(c)    8

(d)    10

15.  One mole of CO2 contains

(a)    6.02 ´ 1023 atoms of C

(b)    6.02 ´ 1023 atoms of O

(c)    18.1 ´ 1023 molecules of CO2

(d)    3 gram of carbon

16.  The number of oxygen atoms is 4.4 g of CO2 is approximately

(a)    1.2 ´ 1023

(b)    6 ´ 1022

(c)    6 ´ 1023

(d)    12 ´ 1022

17. 4.4 g of an unknown gas occupies 2.24 L of volume at Standard temperature and pressure. The gas may be

(a)    Carbon dioxide

(b)    Carbon monoxide

(c)    Oxygen

(d)    Sulphur dioxide

18.  one gram atom of Nitrogen atom corresponds to

(a)    NA molecules of N2

(b)    11.2 L of N2 at STP

(c)    14 g of N2

(d)    22.4 L of N2 at STP

19. The maximum volume of STP is occupied by

(a)    1 g molecule of CO2

(b)    1 g of CO2 of molecule

(c)    0.5 mole of CO2

(d)    44.5 g of CO2

20.  Which of the following represents 1 g mole of the substance

(a)    6.02 ´ 1023 molecules of NH3

(b)    4 g of He

(c)    56 g of CaO

(d)    71 g of Cl2

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