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. 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?

CuCl₃

CuCl

CuCl₂

Cu₂Cl₃

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

50%

20.05%

19.97%

80.03%

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

Molecular formula /n = Empirical formula

Empirical formula x n² = Molecular formula

Empirical formula /n = Molecular formula

Empirical formula x √n = Molecular formula

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

2.24 dm³

112 Cm³

1.12 dm³

22.4 dm³

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

H₂O

NaC1

CC1₄

It can be applied to all

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

NO

N₂O

NO₂

N₂O₃

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

Duma’s method

All of above

K. Jeldahl’s method

Combustion method

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

C₄H₈O₄

C₂H₄O₂

CH₂O

C₃H₆O₃

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

S₂O₃

SO

SO₂

SO₃

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

Air

Vinegar

Water

Oxygen gas

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

5 moles

0.005 mole

5000 mole

10 moles

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13. The modern atomic weight scale is based on

C¹²

O¹⁶

C¹³

H¹

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

Graham’s law of diffusion technique

Osmosis

Fractional distillation technique

Chromatography

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

2:16:2

2:16:1

1:16:2

1:1:1

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

21

42

6

3

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17. What are the parts of an atom?

Ions, electrons, neutrons, water

Nucleus, element, carbon, space

Protons, neutrons, nucleus, mass

Protons, neutrons, electrons, nucleus

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18. 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

Definite proportions

Multiple proportions

Conservation of mass

Constant volume

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

Ionic charges

Ionic element

Ionic atoms

Ionic compounds

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

1.11

0.90

0.11

1.0

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

80

79.5

79

81

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

1, 1, 2, 2, 1

2, 2, 1, 1, 1

2, 2, 1, 2, 1

2, 1, 1, 2, 1

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23. Which of the following represents a compound?

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

Two words in one word

Made up of 10 atoms

A pure substance made up of one type of atom

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

Mixture

Compound

Element

Crystal

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25. The compound having highest percent of oxygen is

CH₃COCH₃

C₂H₅OH

CH₃COOH

H₂O

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26. Difference in density is the basis of

Molecular sieving

Molecular attraction

Ultrafiltration

Gravity separation

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27. 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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28. Which law directly explains the law of conservation of mass?

Dalton’s law

Newton’s law

Hund’s rule

Moley’s law

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

32.47%

66.67%

24.51%

12.26%

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

BaO₂

H₂O₂

C₆H₁₂O₆

C₂H₄

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31. What is a multivalent ion?

Only negatively charged

Some ions can have only one charge

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

An ion that can have more than one charge

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

6.02 x 10²³ x 2

4 x 6.02 x 10²³

3 x 6.02 x 10²³

6.02 x 10²³

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

Sugar

Methane

Water

Carbon dioxide

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

To reduce the time for completion of the reaction

To carry out compete combustion

All of these

To reduce the economy of the process

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

Protons

Ions

Nucleus

Neutrons

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36. Diameter of an atom is in the range of

2 x10¯¹⁰

0.2 m

0.2 Pm

0.2 nm

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37. 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.

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

One moles of N₂ will produce two moles of NH₃.

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38. The prefix 10¹⁸ is

Kilo

Giga

Exa

Nano

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

Mg(ClO₄)₂

SiO₂

KOH

Al₂O₃

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

They possess same chemical properties

They possess different mass number

They possess same position in the periodic table

They possess same physical properties

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41. Empirical formula of chloroform is

CHCl

CH₃cl

CHCl₃

CH₂C₁₂

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42. 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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43. 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

14% hydrogen and 86% carbon

17% hydrogen and 83% carbon

86% hydrogen and 14% carbon

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

CS₂, FeSO₄

CuO, Cu₂O

H₂S, SO₂

NH₃, HC1

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45. Isotopes differ in the

Number of neutrons

Number of atoms

Number of electrons

Number of protons

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

None of these

Lose electrons and protons

Gain electrons and protons

Lose electrons

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

2 elements and a total of 2 atoms

3 elements and a total of 2 atoms

3 elements and a total of 3 atoms

2 elements and a total of 3 atoms

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

Water

Soil

Gold

Sodium Chloride

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50. 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,

Nil, it is dimensionless constant

Newton

Nm¯²s¯²

Kg m¯¹s¯¹

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

3

7

1

4

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52. Which of the following represents an element?

A compound made up of one type of element

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

The periodic table

A pure substance made up of one type of atom

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53. What is the net charge on ferrous ion?

+2

+4

+5

+3

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

0.0233

0.0732

0.210

0.0704

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

MCL₂

MC1₃

M₂C1₂

MC1

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56. The percentage of oxygen in NaOH is

8

40

60

10

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57. Percent of calcium in calcium carbonate is

80%

20%

40%

30%

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58. Which of the following is an element?

Sugar

Common Salt

Gold

Water

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

Electrons and shells

Protons and neutrons

Protons and electrons

Neutrons and electrons

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

3.2 Na

2.4 Na

1.6 Na

4.2 Na

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62. 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 (CH2) is possible

Only one molecular formula (C2H2) is possible

More than one could be a molecular formula for CH₂

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

1.2 x 10²³

6 x 10²²

12 x 10²³

6 x 10²²

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

Mass spectrometer

Ultraviolet spectrometer

Atomic absorption spectrometer

Infra-red spectrometer

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

The atomic mass subtracted the number of protons

The atomic mass plus the number of protons

The atomic mass plus the number of electrons

The atomic mass subtracted the number of electrons

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

Matter always consists of molecules

All matter contains chemical elements

Matter is always composed of atoms

All substances are made of matter

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

0.75

0.25

0.5

1.00

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

44

22

33

11

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69. Which one of the following is ambiguous?

A mole of sodium atoms

A mole of hydrogen

A mole of electrons

A mole of potassium ions

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

Crystallization

Sublimation

Chromatography

Graham’s Law of diffusion

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71. What is a chemical compound?

A subatomic particle

A mixture of two or more substance

A combination of two protons and two electrons

A combination of two or more chemical elements

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