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

Gain electrons and protons

None of these

Lose electrons and protons

Lose electrons

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2. Which of the following represents a compound?

A pure substance made up of one type of atom

Made up of 10 atoms

Two words in one word

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

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3. 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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4. The compound having highest percent of oxygen is

CH₃COOH

C₂H₅OH

CH₃COCH₃

H₂O

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5. 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

4 x 6.02 x 10²³

6.02 x 10²³

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

CS₂, FeSO₄

H₂S, SO₂

CuO, Cu₂O

NH₃, HC1

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

83% hydrogen and 17% carbon

17% hydrogen and 83% carbon

86% hydrogen and 14% carbon

14% hydrogen and 86% carbon

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

2, 2, 1, 2, 1

2, 1, 1, 2, 1

1, 1, 2, 2, 1

2, 2, 1, 1, 1

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

All of above

K. Jeldahl’s method

Duma’s method

Combustion method

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

1.99 x 10¯²³

4.65 x 10¯²³

7.31 x 10¯²³

1.37 x 10²²

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

Mg(ClO₄)₂

SiO₂

Al₂O₃

KOH

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

3

6

21

42

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14. What is a chemical compound?

A subatomic particle

A mixture of two or more substance

A combination of two or more chemical elements

A combination of two protons and two electrons

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15. 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

Constant volume

Definite proportions

Conservation of mass

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

Electrons and shells

Protons and electrons

Protons and neutrons

Neutrons and electrons

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17. 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?

CuCl₂

CuCl

CuCl₃

Cu₂Cl₃

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

2 elements and a total of 2 atoms

3 elements and a total of 3 atoms

3 elements and a total of 2 atoms

2 elements and a total of 3 atoms

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

Ionic compounds

Ionic charges

Ionic element

Ionic atoms

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

All of these

To reduce the time for completion of the reaction

To reduce the economy of the process

To carry out compete combustion

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

6 x 10²²

6 x 10²²

1.2 x 10²³

12 x 10²³

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

Its molecular formula does not exist

Only one molecular formula (C2H2) is possible

More than one could be a molecular formula for CH₂

Only one molecular formula (CH2) is possible

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

Newton’s law

Hund’s rule

Moley’s law

Dalton’s law

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24. What are the parts of an atom?

Ions, electrons, neutrons, water

Protons, neutrons, nucleus, mass

Nucleus, element, carbon, space

Protons, neutrons, electrons, nucleus

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

The atomic mass plus the number of electrons

The atomic mass plus the number of protons

The atomic mass subtracted the number of protons

The atomic mass subtracted the number of electrons

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26. What is a multivalent ion?

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

Only negatively charged

Some ions can have only one charge

An ion that can have more than one charge

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27. What are the two different types of ions?

Electrons and protons

Polyatomic and compound ions

Polyatomic and multivalent

Negative and positive

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

3.01 x 10²³

3.01 x 10²²

6.02 x 10²³

6.02 x 10²²

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29. Which of the following represents an element?

A pure substance made up of one type of atom

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

The periodic table

A compound made up of one type of element

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30. Percent of calcium in calcium carbonate is

80%

30%

40%

20%

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

C₃H₆O₃

CH₂O

C₂H₄O₂

C₄H₈O₄

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

They possess different mass number

They possess same physical properties

They possess same chemical properties

They possess same position in the periodic table

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

0.25

0.75

0.5

1.00

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

Nucleus

Neutrons

Ions

Protons

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35. 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

One moles of N₂ will produce two moles of NH₃.

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

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

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

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36. The percentage of oxygen in NaOH is

8

10

40

60

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

MC1

MC1₃

MCL₂

M₂C1₂

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38. 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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39. The prefix 10¹⁸ is

Nano

Exa

Giga

Kilo

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

Mass spectrometer

Infra-red spectrometer

Ultraviolet spectrometer

Atomic absorption spectrometer

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

12.26%

32.47%

24.51%

66.67%

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

33

44

22

11

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

Air

Water

Oxygen gas

Vinegar

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44. Difference in density is the basis of

Molecular attraction

Gravity separation

Ultrafiltration

Molecular sieving

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45. Which one of the following is ambiguous?

A mole of potassium ions

A mole of sodium atoms

A mole of electrons

A mole of hydrogen

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

Crystallization

Chromatography

Graham’s Law of diffusion

Sublimation

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

NO

NO₂

N₂O₃

N₂O

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48. Empirical formula of chloroform is

CHCl₃

CHCl

CH₃cl

CH₂C₁₂

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49. Which of the following is an element?

Common Salt

Water

Sugar

Gold

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

81

79.5

79

80

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

C₂H₄

C₆H₁₂O₆

H₂O₂

BaO₂

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52. Indicate the incorrect statement form the following

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

Actual yield is always less than theoretical yield

Stoichiometric calculation can only be done if no side reaction happen

A limiting reactant is used at the end of reaction

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

0.005 mole

5 moles

5000 mole

10 moles

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

All matter contains chemical elements

Matter always consists of molecules

Matter is always composed of atoms

All substances are made of matter

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

3

1

7

4

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

Water

Sugar

Methane

Carbon dioxide

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

1.6 Na

2.4 Na

4.2 Na

3.2 Na

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

1.12 dm³

112 Cm³

2.24 dm³

22.4 dm³

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60. The modern atomic weight scale is based on

C¹³

O¹⁶

H¹

C¹²

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61. Isotopes differ in the

Number of protons

Number of electrons

Number of neutrons

Number of atoms

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62. 1 mole of CH₄ contains

4 g-atom of hydrogen

3.0 g of carbon

1.81 x 10²³ molecules of CH₄

6.02 x 10²³ atoms of H

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

SO

S₂O₃

SO₃

SO₂

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

1:16:2

1:1:1

2:16:2

2:16:1

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

CC1₄

H₂O

NaC1

It can be applied to all

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

Empirical formula /n = Molecular formula

Empirical formula x n² = Molecular formula

Molecular formula /n = Empirical formula

Empirical formula x √n = Molecular formula

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67. 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,

Newton

Nil, it is dimensionless constant

Nm¯²s¯²

Kg m¯¹s¯¹

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

20.05%

80.03%

50%

19.97%

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

Sodium Chloride

Gold

Soil

Water

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70. What is the net charge on ferrous ion?

+5

+3

+4

+2

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

Fractional distillation technique

Chromatography

Graham’s law of diffusion technique

Osmosis

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