Basic Concepts of Chemistry Online Mcqs Test

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Question 1

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

Question 2

2. 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 3

3. The prefix 10¹⁸ is

Question 4

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

Answer

Matter always consists of molecules

Answer

All matter contains chemical elements

Answer

All substances are made of matter

Answer

Matter is always composed of atoms

Question 5

5. Diameter of an atom is in the range of

Answer

2 x10¯¹⁰

Question 6

6. What is the net charge on ferrous ion?

Question 7

7. Which one of the following is ambiguous?

Answer

A mole of electrons

Answer

A mole of hydrogen

Answer

A mole of sodium atoms

Answer

A mole of potassium ions

Question 8

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

Answer

1.37 x 10²²

Answer

1.99 x 10¯²³

Answer

4.65 x 10¯²³

Answer

7.31 x 10¯²³

Question 9

9. Which of the following represents an element?

Answer

A compound made up of one type of element

Answer

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

Answer

A pure substance made up of one type of atom

Answer

The periodic table

Question 10

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

Answer

C₃H₆O₃

Answer

C₂H₄O₂

Answer

C₄H₈O₄

Question 11

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

Answer

To reduce the economy of the process

Answer

To carry out compete combustion

Answer

To reduce the time for completion of the reaction

Answer

All of these

Question 12

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

Question 13

13. 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 14

14. Difference in density is the basis of

Answer

Molecular attraction

Answer

Ultrafiltration

Answer

Gravity separation

Answer

Molecular sieving

Question 15

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

Question 16

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

Answer

Empirical formula x √n = Molecular formula

Answer

Empirical formula /n = Molecular formula

Answer

Molecular formula /n = Empirical formula

Answer

Empirical formula x n² = Molecular formula

Question 17

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

Answer

Newton’s law

Answer

Moley’s law

Answer

Hund’s rule

Answer

Dalton’s law

Question 18

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

Answer

CuO, Cu₂O

Answer

CS₂, FeSO₄

Answer

NH₃, HC1

Answer

H₂S, SO₂

Question 19

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

Question 20

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

Question 21

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

Answer

Ionic charges

Answer

Ionic compounds

Answer

Ionic atoms

Answer

Ionic element

Question 22

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

Question 23

23. What are the two different types of ions?

Answer

Polyatomic and compound ions

Answer

Polyatomic and multivalent

Answer

Negative and positive

Answer

Electrons and protons

Question 24

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

Answer

0.005 mole

Question 25

25. Empirical formula of chloroform is

Answer

CH₂C₁₂

Question 26

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

Question 27

27. The modern atomic weight scale is based on

Question 28

28. Indicate the incorrect statement form the following

Answer

Actual yield is always less than theoretical yield

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

Question 29

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

Answer

3 elements and a total of 2 atoms

Answer

2 elements and a total of 2 atoms

Answer

3 elements and a total of 3 atoms

Answer

2 elements and a total of 3 atoms

Question 30

30. What is a chemical compound?

Answer

A combination of two protons and two electrons

Answer

A subatomic particle

Answer

A combination of two or more chemical elements

Answer

A mixture of two or more substance

Question 31

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

Question 32

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

Question 33

33. 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 34

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

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

Answer

The atomic mass plus the number of electrons

Question 35

35. What are the parts of an atom?

Answer

Nucleus, element, carbon, space

Answer

Ions, electrons, neutrons, water

Answer

Protons, neutrons, electrons, nucleus

Answer

Protons, neutrons, nucleus, mass

Question 36

36. What is a multivalent ion?

Answer

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

Answer

An ion that can have more than one charge

Answer

Only negatively charged

Answer

Some ions can have only one charge

Question 37

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

Question 38

38. 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

6.02 x 10²²

Answer

3.01 x 10²²

Question 39

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

Answer

C₆H₁₂O₆

Question 40

40. The compound having highest percent of oxygen is

Answer

CH₃COCH₃

Answer

C₂H₅OH

Question 41

41. Which of the following represents a compound?

Answer

Made up of 10 atoms

Answer

A pure substance made up of one type of atom

Answer

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

Answer

Two words in one word

Question 42

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

Answer

2, 2, 1, 1, 1

Answer

2, 2, 1, 2, 1

Answer

1, 1, 2, 2, 1

Answer

2, 1, 1, 2, 1

Question 43

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

Question 44

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

Question 45

45. 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

Nil, it is dimensionless constant

Answer

Kg m¯¹s¯¹

Answer

Nm¯²s¯²

Question 46

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

Answer

Sodium Chloride

Question 47

47. 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

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

Answer

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

Answer

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

Answer

One moles of N₂ will produce two moles of NH₃.

Question 48

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

Question 49

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

Question 50

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

Answer

Crystallization

Answer

Sublimation

Answer

Chromatography

Answer

Graham’s Law of diffusion

Question 51

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

Question 52

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

Answer

Lose electrons and protons

Answer

None of these

Answer

Lose electrons

Answer

Gain electrons and protons

Question 53

53. 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 54

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

Answer

Fractional distillation technique

Answer

Graham’s law of diffusion technique

Answer

Chromatography

Question 55

55. 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 56

56. The percentage of oxygen in NaOH is

Question 57

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

Answer

Infra-red spectrometer

Answer

Atomic absorption spectrometer

Answer

Ultraviolet spectrometer

Answer

Mass spectrometer

Question 58

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

Answer

They possess different mass number

Answer

They possess same physical properties

Answer

They possess same position in the periodic table

Answer

They possess same chemical properties

Question 59

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

Question 60

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

Answer

1.2 x 10²³

Answer

6 x 10²²

Answer

12 x 10²³

Answer

6 x 10²²

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. Isotopes differ in the

Answer

Number of protons

Answer

Number of electrons

Answer

Number of neutrons

Answer

Number of atoms

Question 63

63. Percent of calcium in calcium carbonate is

Question 64

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

Answer

Only one molecular formula (C2H2) is possible

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 140

4 g-atom of hydrogen

Answer 141

6.02 x 10²³ atoms of H

Answer 142

3.0 g of carbon

Answer 143

1.81 x 10²³ molecules of CH₄

Answer 144

6.02 x 10²³ x 2

Answer 145

3 x 6.02 x 10²³

Answer 146

6.02 x 10²³

Answer 147

4 x 6.02 x 10²³

Answer 148

It can be applied to all

Answer 149

Conservation of mass

Answer 150

Multiple proportions

Answer 151

Constant volume

Answer 152

Definite proportions

Answer 153

Common Salt

Answer 154

K. Jeldahl’s method

Answer 155

All of above

Answer 156

Duma’s method

Answer 157

Combustion method

Answer 158

Oxygen gas

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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