Basic Concepts of Chemistry Online Mcqs Test

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

2. Percent of calcium in calcium carbonate is

3. Diameter of an atom is in the range of

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

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

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

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

8. Empirical formula of chloroform is

9. The modern atomic weight scale is based on

10. The prefix 10¹⁸ is

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

12. 1 mole of CH₄ contains

13. What is a multivalent ion?

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

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

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

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

18. What is a chemical compound?

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

20. What are the parts of an atom?

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

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

23. 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

24. What is the net charge on ferrous ion?

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

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

27. Difference in density is the basis of

28. Which of the following represents an element?

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

30. 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?

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

32. The percentage of oxygen in NaOH is

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

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

35. Which of the following represents a compound?

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

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

38. Which one of the following is ambiguous?

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

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

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

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

43. 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

44. The compound having highest percent of oxygen is

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

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

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

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

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

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

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

52. Indicate the incorrect statement form the following

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

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

55. Which of the following is an element?

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

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

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

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

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

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

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

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

64. What are the two different types of ions?

65. 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,

66. Isotopes differ in the

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

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

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

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

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