Basic Concepts of Chemistry Online Mcqs Test

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Question 1

1. What is correct relationship between empirical and molecular formulas?

Answer

Molecular formula /n = Empirical formula

Answer

Empirical formula x n² = Molecular formula

Answer

Empirical formula /n = Molecular formula

Answer

Empirical formula x √n = Molecular formula

Question 2

2. How can you separate the mixture of two gases of different atomic masses?

Answer

Crystallization

Answer

Chromatography

Answer

Sublimation

Answer

Graham’s Law of diffusion

Question 3

3. 1 mole of CH₄ contains

Answer

3.0 g of carbon

Answer

6.02 x 10²³ atoms of H

Answer

1.81 x 10²³ molecules of CH₄

Answer

4 g-atom of hydrogen

Question 4

4. Which of the following represents an element?

Answer

The periodic table

Answer

A pure substance made up of two or more types of atoms

Answer

A compound made up of one type of element

Answer

A pure substance made up of one type of atom

Question 5

5. A ring contains 1.2g of diamond. How many number of carbon atoms are in diamond?

Answer

6.02 x 10²³

Answer

3.01 x 10²³

Answer

3.01 x 10²²

Answer

6.02 x 10²²

Question 6

6. If the empirical formula of compound is CH₂. Which of the following is true about its molecular formula?

Answer

Only one molecular formula (CH2) is possible

Answer

Its molecular formula does not exist

Answer

More than one could be a molecular formula for CH₂

Answer

Only one molecular formula (C2H2) is possible

Question 7

7. How many elements are present in two molecules of aspirin? The formula for aspirin is C₉H₈O₄.

Question 8

8. Most atoms are neutral, to become a positive ion the atom must:

Answer

Lose electrons and protons

Answer

Gain electrons and protons

Answer

None of these

Answer

Lose electrons

Question 9

9. An oxide of nitrogen contain 36.8% nitrogen and 63.2% oxygen by mass. Calculate its empirical formula.

Question 10

10. Which of the following is NOT true of matter on the Earth?

Answer

Matter is always composed of atoms

Answer

All matter contains chemical elements

Answer

All substances are made of matter

Answer

Matter always consists of molecules

Question 11

11. How many moles of Helium gas occupy 22.4 L at 0°C at 1 atm. Pressure?

Question 12

12. Vapor density of a gas is 22. What is its molecular mass?

Question 13

13. How many number of ions are there in 98 grams of sulphate ions?

Answer

3 x 6.02 x 10²³

Answer

4 x 6.02 x 10²³

Answer

6.02 x 10²³

Answer

6.02 x 10²³ x 2

Question 14

14. Which of the following could be an empirical formula?

Answer

C₆H₁₂O₆

Question 15

15. The set of numerical coefficients that balances the chemical equation K₂CrO₄ + CH1 → K₂Cr₂O₇ + KC1 + H₂O

Answer

2, 2, 1, 2, 1

Answer

1, 1, 2, 2, 1

Answer

2, 1, 1, 2, 1

Answer

2, 2, 1, 1, 1

Question 16

16. Which law directly explains the law of conservation of mass?

Answer

Newton’s law

Answer

Hund’s rule

Answer

Dalton’s law

Answer

Moley’s law

Question 17

17. How many moles of KBrO₃ are required to prepare 0.0700 moles of Br₂ according to the reaction: KBrO₃ + 5KBr + 6HNO₃ → 6KNO₃ + 3Br₂ + 3H₂O

Question 18

18. Isotopes differ in the

Answer

Number of protons

Answer

Number of atoms

Answer

Number of electrons

Answer

Number of neutrons

Question 19

19. Bromine has two isotopes having the relative abundances as ⁷⁵₃₉Br = 50.51% and ⁸¹₃₅Br= 49.49%. The average atomic mass of bromine is

Question 20

20. The empirical formula of a compound is CH₂O and its molecular mass is 120. The molecular formula of the compound is

Answer

C₄H₈O₄

Answer

C₂H₄O₂

Answer

C₃H₆O₃

Question 21

21. Ayesha required an aqueous solution of sodium chloride. She made the solution by dissolving salt in:

Answer

Oxygen gas

Question 22

22. The coefficient of viscosity η of a fluid moving steadily between two surfaces is given by the formula, f = η dV/dx where f is the frictional force on the fluid. A is an area in the fluid and dV/dx is the velocity gradient inside the fluid at that area. The S.I. unit of viscosity coefficient η is given as,

Answer

Nm¯²s¯²

Answer

Kg m¯¹s¯¹

Answer

Nil, it is dimensionless constant

Question 23

23. Which of the following method is used to estimate oxygen in an organic compound?

Answer

K. Jeldahl’s method

Answer

Duma’s method

Answer

Combustion method

Answer

All of above

Question 24

24. Indicate the incorrect statement form the following

Answer

The empirical and molecular formula of some of the compounds are same

Answer

Stoichiometric calculation can only be done if no side reaction happen

Answer

A limiting reactant is used at the end of reaction

Answer

Actual yield is always less than theoretical yield

Question 25

25. Which one of the following is ambiguous?

Answer

A mole of sodium atoms

Answer

A mole of hydrogen

Answer

A mole of potassium ions

Answer

A mole of electrons

Question 26

26. One of the substances is used to absorb CO₂ gas in combustion analysis. Which is that substance?

Answer

Mg(ClO₄)₂

Question 27

27. What is a multivalent ion?

Answer

An ion that can have more than one charge

Answer

Only negatively charged

Answer

Ions that are made of more than one type of atom and act as one

Answer

Some ions can have only one charge

Question 28

28. What are the two different types of ions?

Answer

Negative and positive

Answer

Polyatomic and multivalent

Answer

Polyatomic and compound ions

Answer

Electrons and protons

Question 29

29. How many moles of CO₂ are present in 220 mg?

Answer

0.005 mole

Question 30

30. A compound contains 6.0 g of carbon and 1.0 g of hydrogen. The percent composition of the compound is:

Answer

86% hydrogen and 14% carbon

Answer

83% hydrogen and 17% carbon

Answer

14% hydrogen and 86% carbon

Answer

17% hydrogen and 83% carbon

Question 31

31. What are the ratios among the volumes of gases of ³²O₂,²H₂, and ¹⁶CH₄ if equal mass of each gas is taken?

Question 32

32. If Na is Avogadro’s number, then number of valence electrons in 4.2 g of nitride ions N³¯ is

Question 33

33. To differentiate between C-12, C-13 and C-14, the instrument that you would use is

Answer

Atomic absorption spectrometer

Answer

Ultraviolet spectrometer

Answer

Mass spectrometer

Answer

Infra-red spectrometer

Question 34

34. What is a chemical compound?

Answer

A mixture of two or more substance

Answer

A combination of two or more chemical elements

Answer

A combination of two protons and two electrons

Answer

A subatomic particle

Question 35

35. Which of the following is NOT a pure substance?

Answer

Sodium Chloride

Question 36

36. Percent of calcium in calcium carbonate is

Question 37

37. For which of the following terms empirical formula cannot be applied?

Answer

It can be applied to all

Question 38

38. The Number of oxygen atoms in 4.4 g of CO2 is approximately

Answer

12 x 10²³

Answer

1.2 x 10²³

Answer

6 x 10²²

Answer

6 x 10²²

Question 39

39. How do you calculate the number of neutrons in an atom?

Answer

The atomic mass plus the number of protons

Answer

The atomic mass subtracted the number of electrons

Answer

The atomic mass plus the number of electrons

Answer

The atomic mass subtracted the number of protons

Question 40

40. An anhydrous salt of copper is found to contain 52.7% chlorine and 47.3% copper by mass. What is the empirical formula for this salt?

Answer

Cu₂Cl₃

Question 41

41. What is the net charge on ferrous ion?

Question 42

42. Which of the following statements is wrong about isotopes?

Answer

They possess same position in the periodic table

Answer

They possess same physical properties

Answer

They possess different mass number

Answer

They possess same chemical properties

Question 43

43. Copper (II) oxide is mixed with organic compound during combustion. The purpose is

Answer

To reduce the economy of the process

Answer

All of these

Answer

To reduce the time for completion of the reaction

Answer

To carry out compete combustion

Question 44

44. Which of the following is a pure substance made up of two or more types of atoms or elements?

Question 45

45. The modern atomic weight scale is based on

Question 46

46. Which of the following statements is FALSE for the chemical equation given below in which nitrogen gas reacts with hydrogen gas to form ammonia gas assuming the reaction goes to completion?
N₂ + 3H₂ → 2NH₃

Answer

One molecule of nitrogen requires three molecules of hydrogen for complete reaction.

Answer

One moles of N₂ will produce two moles of NH₃.

Answer

The reaction of one mole of H₂ will produce 2/3 moles of NH₃.

Answer

The reaction of three moles of hydrogen gas will produce 17 g of ammonia

Question 47

47. Empirical formula of chloroform is

Answer

CH₂C₁₂

Question 48

48. The percentage of oxygen in NaOH is

Question 49

49. A gaseous mixture contains 50% helium and 50% methane by volume. What is the percent by weight of methane in the mixture?

Question 50

50. What is the percent water in hydrated calcium chloride (CaC1₂ 2H₂O)?

Question 51

51. What does the atomic number of an atom represent?

Answer

Electrons and shells

Answer

Protons and neutrons

Answer

Neutrons and electrons

Answer

Protons and electrons

Question 52

52. Since atoms are neutral, the number of electrons is equal to the number of:

Question 53

53. Which of the following is an element?

Answer

Common Salt

Question 54

54. How will you separate a mixture of two gases?

Answer

Graham’s law of diffusion technique

Answer

Chromatography

Answer

Fractional distillation technique

Question 55

55. Water (H₂O) is a common compound made up of:

Answer

3 elements and a total of 2 atoms

Answer

3 elements and a total of 3 atoms

Answer

2 elements and a total of 2 atoms

Answer

2 elements and a total of 3 atoms

Question 56

56. The prefix 10¹⁸ is

Question 57

57. What do you call pure substances that are formed from the attraction between positive ions and negative ions?

Answer

Ionic compounds

Answer

Ionic charges

Answer

Ionic atoms

Answer

Ionic element

Question 58

58. Calculate the weight, in grams, of one molecule of carbon dioxide, CO₂.

Answer

1.37 x 10²²

Answer

7.31 x 10¯²³

Answer

1.99 x 10¯²³

Answer

4.65 x 10¯²³

Question 59

59. Which of the following represents a compound?

Answer

Made up of 10 atoms

Answer

Pure substances made up to of 2 or more types of atoms

Answer

Two words in one word

Answer

A pure substance made up of one type of atom

Question 60

60. Irrespective of the source, pure sample of water always yields 88.89% mass of oxygen and 11.11% mass of hydrogen. This is explained by the law of

Answer

Conservation of mass

Answer

Constant volume

Answer

Multiple proportions

Answer

Definite proportions

Question 61

61. The empirical formula of the compound having 50% sulphur and 50% oxygen by mass is

Question 62

62. Diameter of an atom is in the range of

Answer

2 x10¯¹⁰

Question 63

63. What are the parts of an atom?

Answer

Ions, electrons, neutrons, water

Answer

Nucleus, element, carbon, space

Answer

Protons, neutrons, electrons, nucleus

Answer

Protons, neutrons, nucleus, mass

Question 64

64. Difference in density is the basis of

Answer

Molecular sieving

Answer

Molecular attraction

Answer

Gravity separation

Answer

Ultrafiltration

Answer 152

Carbon dioxide

Answer 153

H₂S, SO₂

Answer 154

NH₃, HC1

Answer 155

CS₂, FeSO₄

Answer 156

CuO, Cu₂O

Answer 157

CH₃COCH₃

Answer 158

C₂H₅OH

Total Questions:	71
Time Allowed:	30 Minutes
Total Marks:	71
How to Attempt Test:	Please choose the right Option in MCQ-type question.
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