MDCAT Fundamental Concepts of Chemistry Test Online MCQs

MDCAT Fundamental Concepts of Chemistry Online Test

Prepare for MDCAT Chemistry with this online MCQ test on Fundamental Concepts of Chemistry. This quiz covers key basics such as atomic mass, moles, empirical and molecular formulas, and chemical calculations, aligned with the MDCAT 2025 syllabus to build a strong foundation for the subject.

MDCAT 2025 Basic Concepts Online Test

MDCAT Chemistry Basic Concepts Test Question with Answer

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1. Which of the following is an element?

Common Salt

Gold

Water

Sugar

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2. Isotopes differ in the

Number of atoms

Number of electrons

Number of protons

Number of neutrons

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

4

7

3

1

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

Ionic element

Ionic charges

Ionic compounds

Ionic atoms

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

66.67%

24.51%

12.26%

32.47%

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6. What are the two different types of ions?

Negative and positive

Polyatomic and multivalent

Electrons and protons

Polyatomic and compound ions

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

The atomic mass plus the number of protons

The atomic mass subtracted the number of electrons

The atomic mass plus the number of electrons

The atomic mass subtracted the number of protons

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8. Which of the following represents an element?

The periodic table

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

A pure substance made up of one type of atom

A compound made up of one type of element

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9. Diameter of an atom is in the range of

0.2 m

0.2 Pm

0.2 nm

2 x10¯¹⁰

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

Empirical formula x √n = Molecular formula

Empirical formula /n = Molecular formula

Molecular formula /n = Empirical formula

Empirical formula x n² = Molecular formula

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11. 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

Multiple proportions

Definite proportions

Conservation of mass

Constant volume

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

1.0

1.11

0.90

0.11

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

1:1:1

2:16:1

2:16:2

1:16:2

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

NO

N₂O₃

N₂O

NO₂

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

CuO, Cu₂O

H₂S, SO₂

NH₃, HC1

CS₂, FeSO₄

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

Neutrons and electrons

Electrons and shells

Protons and neutrons

Protons and electrons

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

3.01 x 10²²

6.02 x 10²³

6.02 x 10²²

3.01 x 10²³

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18. 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?

Cu₂Cl₃

CuCl₂

CuCl

CuCl₃

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

19.97%

50%

80.03%

20.05%

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

81

79

79.5

80

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

33

11

22

44

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

To reduce the economy of the process

All of these

To carry out compete combustion

To reduce the time for completion of the reaction

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23. 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,

Kg m¯¹s¯¹

Newton

Nm¯²s¯²

Nil, it is dimensionless constant

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

3.2 Na

1.6 Na

2.4 Na

4.2 Na

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

2, 2, 1, 1, 1

2, 2, 1, 2, 1

2, 1, 1, 2, 1

1, 1, 2, 2, 1

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

86% hydrogen and 14% carbon

14% hydrogen and 86% carbon

17% hydrogen and 83% carbon

83% hydrogen and 17% carbon

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

Graham’s Law of diffusion

Chromatography

Sublimation

Crystallization

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

Mg(ClO₄)₂

KOH

SiO₂

Al₂O₃

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

3

42

6

21

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

They possess same chemical properties

They possess same position in the periodic table

They possess different mass number

They possess same physical properties

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

6 x 10²²

1.2 x 10²³

6 x 10²²

12 x 10²³

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

More than one could be a molecular formula for CH₂

Its molecular formula does not exist

Only one molecular formula (C2H2) is possible

Only one molecular formula (CH2) is possible

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33. Indicate the incorrect statement form the following

A limiting reactant is used at the end of reaction

Actual yield is always less than theoretical yield

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

Stoichiometric calculation can only be done if no side reaction happen

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34. The modern atomic weight scale is based on

C¹²

O¹⁶

H¹

C¹³

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

MCL₂

M₂C1₂

MC1

MC1₃

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

22.4 dm³

112 Cm³

1.12 dm³

2.24 dm³

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

Graham’s law of diffusion technique

Osmosis

Fractional distillation technique

Chromatography

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38. Which one of the following is ambiguous?

A mole of hydrogen

A mole of potassium ions

A mole of electrons

A mole of sodium atoms

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

Soil

Water

Gold

Sodium Chloride

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

NaC1

H₂O

It can be applied to all

CC1₄

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41. The percentage of oxygen in NaOH is

8

60

40

10

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

Mass spectrometer

Atomic absorption spectrometer

Ultraviolet spectrometer

Infra-red spectrometer

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43. The prefix 10¹⁸ is

Exa

Nano

Kilo

Giga

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

Nucleus

Ions

Protons

Neutrons

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

3 elements and a total of 3 atoms

2 elements and a total of 3 atoms

3 elements and a total of 2 atoms

2 elements and a total of 2 atoms

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

5 moles

10 moles

5000 mole

0.005 mole

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47. What is a multivalent ion?

Only negatively charged

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

An ion that can have more than one charge

Some ions can have only one charge

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

0.25

0.5

0.75

1.00

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

Carbon dioxide

Methane

Water

Sugar

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50. What is the net charge on ferrous ion?

+4

+2

+3

+5

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51. Which of the following represents a compound?

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

A pure substance made up of one type of atom

Two words in one word

Made up of 10 atoms

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

All substances are made of matter

All matter contains chemical elements

Matter always consists of molecules

Matter is always composed of atoms

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

SO₂

SO

S₂O₃

SO₃

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

C₃H₆O₃

C₂H₄O₂

C₄H₈O₄

CH₂O

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

K. Jeldahl’s method

All of above

Combustion method

Duma’s method

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56. 1 mole of CH₄ contains

4 g-atom of hydrogen

1.81 x 10²³ molecules of CH₄

6.02 x 10²³ atoms of H

3.0 g of carbon

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

1.99 x 10¯²³

7.31 x 10¯²³

1.37 x 10²²

4.65 x 10¯²³

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

6.02 x 10²³ x 2

3 x 6.02 x 10²³

6.02 x 10²³

4 x 6.02 x 10²³

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

BaO₂

C₆H₁₂O₆

H₂O₂

C₂H₄

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

Mixture

Element

Compound

Crystal

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61. Difference in density is the basis of

Molecular sieving

Molecular attraction

Ultrafiltration

Gravity separation

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62. 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

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

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

One moles of N₂ will produce two moles of NH₃.

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

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

Lose electrons and protons

Gain electrons and protons

Lose electrons

None of these

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64. Empirical formula of chloroform is

CHCl₃

CH₃cl

CH₂C₁₂

CHCl

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65. Percent of calcium in calcium carbonate is

40%

30%

80%

20%

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66. The compound having highest percent of oxygen is

H₂O

CH₃COCH₃

CH₃COOH

C₂H₅OH

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

Dalton’s law

Hund’s rule

Moley’s law

Newton’s law

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68. What are the parts of an atom?

Protons, neutrons, nucleus, mass

Ions, electrons, neutrons, water

Nucleus, element, carbon, space

Protons, neutrons, electrons, nucleus

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69. What is a chemical compound?

A combination of two or more chemical elements

A mixture of two or more substance

A subatomic particle

A combination of two protons and two electrons

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

Oxygen gas

Vinegar

Air

Water

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

0.210

0.0732

0.0704

0.0233

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