Basic Concepts of Chemistry Online Mcqs Test

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Question 1

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

Answer

Gain electrons and protons

Answer

Lose electrons

Answer

None of these

Answer

Lose electrons and protons

Question 2

2. Calculate the number of moles of CaCO₃ (Formula weight = 100) in a sample that weighs 25.0 grams.

Question 3

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

Question 4

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

Question 5

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

Question 6

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

Answer

2, 1, 1, 2, 1

Answer

2, 2, 1, 1, 1

Answer

1, 1, 2, 2, 1

Answer

2, 2, 1, 2, 1

Question 7

7. What is the net charge on ferrous ion?

Question 8

8. The modern atomic weight scale is based on

Question 9

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

Answer

12 x 10²³

Answer

6 x 10²²

Answer

1.2 x 10²³

Answer

6 x 10²²

Question 10

10. Which of the following represents an element?

Answer

A compound made up of one type of element

Answer

A pure substance made up of one type of atom

Answer

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

Answer

The periodic table

Question 11

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

Answer

Ultraviolet spectrometer

Answer

Infra-red spectrometer

Answer

Atomic absorption spectrometer

Answer

Mass spectrometer

Question 12

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

Answer

C₆H₁₂O₆

Question 13

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

Question 14

14. Balance the following equation using minimum integral coefficients: (NH₃ + O₂ → NO₂ + H₂O) Find the stoichiometric coefficient for oxygen gas O₂:

Question 15

15. What is a multivalent ion?

Answer

An ion that can have more than one charge

Answer

Some ions can have only one charge

Answer

Only negatively charged

Answer

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

Question 16

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

Answer

Dalton’s law

Answer

Newton’s law

Answer

Hund’s rule

Answer

Moley’s law

Question 17

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

Question 18

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

Answer

Ionic atoms

Answer

Ionic element

Answer

Ionic charges

Answer

Ionic compounds

Question 19

19. The percentage of oxygen in NaOH is

Question 20

20. What are the two different types of ions?

Answer

Polyatomic and multivalent

Answer

Electrons and protons

Answer

Negative and positive

Answer

Polyatomic and compound ions

Question 21

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

Question 22

22. 1 mole of CH₄ contains

Answer

4 g-atom of hydrogen

Answer

1.81 x 10²³ molecules of CH₄

Answer

3.0 g of carbon

Answer

6.02 x 10²³ atoms of H

Question 23

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

Answer

They possess different mass number

Answer

They possess same position in the periodic table

Answer

They possess same chemical properties

Answer

They possess same physical properties

Question 24

24. Which of the following represents a compound?

Answer

Two words in one word

Answer

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

Answer

A pure substance made up of one type of atom

Answer

Made up of 10 atoms

Question 25

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

Answer

2 elements and a total of 3 atoms

Answer

2 elements and a total of 2 atoms

Answer

3 elements and a total of 3 atoms

Answer

3 elements and a total of 2 atoms

Question 26

26. Among the following pairs, the one which illustrates the law of multiple proportions is

Answer

H₂S, SO₂

Answer

CS₂, FeSO₄

Answer

NH₃, HC1

Answer

CuO, Cu₂O

Question 27

27. 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 28

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

Answer

83% hydrogen and 17% carbon

Answer

17% hydrogen and 83% carbon

Answer

86% hydrogen and 14% carbon

Answer

14% hydrogen and 86% carbon

Question 29

29. 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 30

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

Question 31

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

Answer

It can be applied to all

Question 32

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

Question 33

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

Answer

More than one could be a molecular formula for CH₂

Answer

Its molecular formula does not exist

Answer

Only one molecular formula (CH2) is possible

Answer

Only one molecular formula (C2H2) is possible

Question 34

34. 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 35

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

Answer

Sodium Chloride

Question 36

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

Answer

Graham’s Law of diffusion

Answer

Sublimation

Answer

Chromatography

Answer

Crystallization

Question 37

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

Answer

To carry out compete combustion

Answer

All of these

Answer

To reduce the time for completion of the reaction

Answer

To reduce the economy of the process

Question 38

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

Answer

0.005 mole

Question 39

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

Question 40

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

Question 41

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

Question 42

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

Answer

Protons and electrons

Answer

Protons and neutrons

Answer

Electrons and shells

Answer

Neutrons and electrons

Question 43

43. The compound having highest percent of oxygen is

Answer

C₂H₅OH

Answer

CH₃COCH₃

Question 44

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

Question 45

45. The volume occupied by 28 gram of N₂ at STP?

Question 46

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

Answer

Fractional distillation technique

Answer

Graham’s law of diffusion technique

Answer

Chromatography

Question 47

47. Which of the following is an element?

Answer

Common Salt

Question 48

48. The hydrogen phosphate of certain metal has formula MHPO₄. The formula of metal chloride would be

Question 49

49. What is a chemical compound?

Answer

A subatomic particle

Answer

A combination of two or more chemical elements

Answer

A mixture of two or more substance

Answer

A combination of two protons and two electrons

Question 50

50. Molecular compounds can be found in all three states of matter at room temperature. Which molecule compound is a liquid at room temperature?

Answer

Carbon dioxide

Question 51

51. 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 52

52. 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

Definite proportions

Answer

Multiple proportions

Question 53

53. 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 three moles of hydrogen gas will produce 17 g of ammonia

Answer

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

Question 54

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

Answer

6.02 x 10²³

Answer

6.02 x 10²²

Answer

3.01 x 10²³

Answer

3.01 x 10²²

Question 55

55. Diameter of an atom is in the range of

Answer

2 x10¯¹⁰

Question 56

56. 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 x 2

Answer

6.02 x 10²³

Question 57

57. Which one of the following is ambiguous?

Answer

A mole of sodium atoms

Answer

A mole of electrons

Answer

A mole of potassium ions

Answer

A mole of hydrogen

Question 58

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

Answer

Matter always consists of molecules

Answer

All substances are made of matter

Answer

All matter contains chemical elements

Answer

Matter is always composed of atoms

Question 59

59. The prefix 10¹⁸ is

Question 60

60. Difference in density is the basis of

Answer

Ultrafiltration

Answer

Molecular sieving

Answer

Gravity separation

Answer

Molecular attraction

Question 61

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

Answer

Mg(ClO₄)₂

Question 62

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

Answer

The atomic mass plus the number of electrons

Answer

The atomic mass subtracted the number of electrons

Answer

The atomic mass plus the number of protons

Answer

The atomic mass subtracted the number of protons

Question 63

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

Answer

1.99 x 10¯²³

Answer

1.37 x 10²²

Answer

7.31 x 10¯²³

Answer

4.65 x 10¯²³

Question 64

64. Isotopes differ in the

Answer

Number of electrons

Answer

Number of protons

Answer

Number of atoms

Answer

Number of neutrons

Answer 142

Kg m¯¹s¯¹

Answer 143

Nil, it is dimensionless constant

Answer 144

Nm¯²s¯²

Answer 145

Protons, neutrons, electrons, nucleus

Answer 146

Nucleus, element, carbon, space

Answer 147

Ions, electrons, neutrons, water

Answer 148

Protons, neutrons, nucleus, mass

Answer 149

Oxygen gas

Answer 150

CH₂C₁₂

Answer 151

Actual yield is always less than theoretical yield

Answer 152

Stoichiometric calculation can only be done if no side reaction happen

Answer 153

A limiting reactant is used at the end of reaction

Answer 154

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

Answer 155

Combustion method

Answer 156

Duma’s method

Answer 157

All of above

Answer 158

K. Jeldahl’s method

Total Questions:	71
Time Allowed:	30 Minutes
Total Marks:	71
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