Multiple Choice Questions
ATOMS AND MOLECULES
Practice Questions with Answers
Total 88 questions available
Q. 1
What are the building blocks of matter?
A
AtomsB
CompoundC
MoleculesD
ElementClick an option to check your answer
Q. 2
Cl₂ stands for:
A
2 ions of chlorineB
2 molecules of chlorineC
3 molecules of chlorineD
2 atoms of chlorineClick an option to check your answer
Q. 3
What kind of particles do ionic compounds consist of?
A
IonsB
AtomsC
ElementsD
MoleculesClick an option to check your answer
Q. 4
How are the elements in a chemical formula typically arranged?
A
RandomlyB
Metals first, then non-metalsC
Non-metals firstD
AlphabeticallyClick an option to check your answer
Q. 5
What is the difference between molecular mass and formula unit mass?
A
NoneB
Molecular mass is for covalent compounds; formula unit mass is for ionic compoundsC
Molecular mass is always higherD
They are the sameClick an option to check your answer
Q. 6
Which of the following is the correct IUPAC symbol for the element Cobalt?
A
CoB
CbC
CD
none of theseClick an option to check your answer
Q. 7
Which atom is the smallest atom of all?
A
HydrogenB
LithiumC
HeliumD
CarbonClick an option to check your answer
Q. 8
What is an atom?
A
Smallest particle of a compoundB
Smallest particle of a mixtureC
Largest particle of an elementD
Smallest particle of an elementClick an option to check your answer
Q. 9
How do atoms usually exist in nature?
A
In the free stateB
In the form of moleculesC
In the form of ionsD
In the form of molecules and IonsClick an option to check your answer
Q. 10
Who gave the Law of constant proportions?
A
DaltonB
CavendishC
ProustD
LavoisierClick an option to check your answer
Q. 11
1 u or 1 amu means
A
Mass of O-16 atomB
1/12th mass of C-12 atomsC
Mass of C-12 atomD
Mass of Hydrogen moleculeClick an option to check your answer
Q. 12
In the formula Mg(OH)₂, what does the "2" outside the brackets indicate?
A
2 H atomsB
2 OH ionsC
2 O atomsD
2 Mg atomsClick an option to check your answer
Q. 13
Which of the following is the correct pair of elements and its symbol?
A
Potassium – PtB
Sodium – SoC
Sulphur – SD
Silver – SiClick an option to check your answer
Q. 14
What does the term "atomicity" refer to?
A
Mass of an atomB
Number of atoms in a moleculeC
Size of an atomD
Number of protons in an atomClick an option to check your answer
Q. 15
The balancing of chemical equations is based upon:
A
Law of combining volumesB
Law of definite proportionC
Law of conservation of massD
Law of multiple proportionsClick an option to check your answer
Q. 16
Law of conservation of mass can be derived from which postulate of Dalton’s atomic theory?
A
Matter is made of tiny particles.B
Atoms of a given element have the same mass.C
Atom can neither be created nor destroyed.D
The relative number and kind of atoms are constant in a given compound.Click an option to check your answer
Q. 17
What is the formula for sodium chloride?
A
NaCl₃B
NaCl₂C
Na₂ClD
NaClClick an option to check your answer
Q. 18
One atomic mass unit is a mass unit equal to exactly one twelfth of the mass of ___________.
A
Carbon-1B
Nitrogen -14C
Silicon-14D
Carbon-12Click an option to check your answer
Q. 19
Calculate the formula unit mass of ZnCl2?
A
123 uB
136.3 uC
111 uD
124 uClick an option to check your answer
Q. 20
The atomic mass of sodium is 23. The number of moles in 46g of sodium is ________.
A
2B
0C
4D
½Click an option to check your answer
Q. 21
Molecules of compounds are made up of the same type of atoms.
A
TrueB
FalseClick an option to check your answer
Q. 22
Which of the following can be used to see atoms?
A
MicroscopeB
Optical microscopeC
Most powerful microscopeD
Scanning tunneling microscopeClick an option to check your answer
Q. 23
9 grams of water decompose to give:
A
4g oxygen and 16g hydrogenB
2g hydrogen and 1g oxygenC
8g oxygen and 1g hydrogenD
noneClick an option to check your answer
Q. 24
What does the Law of Constant Proportions tell us about chemical compounds?
A
They have elements that vary in mass randomlyB
They contain different elements in different proportionsC
They change their elements when prepared differentlyD
They always have the same elements in the same proportion by massClick an option to check your answer
Q. 25
How are the names of elements typically derived?
A
RandomlyB
From places or namesC
From numbersD
From colorsClick an option to check your answer
Q. 26
Which is the smallest particle of an element that can take part in a chemical reaction?
A
CompoundB
MixtureC
MoleculeD
AtomClick an option to check your answer
Q. 27
Which of the following represents the correct relation between Avogadro's number (N₀), number of particles (N), and moles (n)?
A
n = N / N₀B
n = N₀ / NC
n = N N₀D
All are correctClick an option to check your answer
Q. 28
Which type of reaction verifies the law of conservation of mass?
A
Displacement reactionB
Decomposition reactionC
Double decomposition reactionD
Precipitation reactionClick an option to check your answer
Q. 29
Atoms of a given element are different in mass and chemical properties.
A
FalseB
TrueClick an option to check your answer
Q. 30
Which of the following statements is not true about an atom?
A
Atoms are the basic units from which molecules and ions are formed.B
Atoms are not able to exist independently.C
Atoms are always neutral in nature.D
Atoms aggregate in large numbers to form matter.Click an option to check your answer
Q. 31
Which element's atomic mass was originally used as a standard before carbon-12?
A
HydrogenB
OxygenC
NitrogenD
NoneClick an option to check your answer
Q. 32
What is the molecular mass of nitric acid (HNO₃)?
A
70 uB
64 uC
63 uD
58 uClick an option to check your answer
Q. 33
Which of the following contains the maximum number of molecules?
A
19 CO₂B
1 g CH₄C
1 g N₂D
1 g H₂Click an option to check your answer
Q. 34
A student heats 25g of reactant ‘A’ with 50g of reactant ‘B’... What law is confirmed?
A
Law of conservation of massB
Law of constant proportionC
Law of multiple proportionsD
Law of conservation of mass and Law of constant proportionClick an option to check your answer
Q. 35
Molecules can exist in free state because:
A
They are very stableB
They are electrically chargedC
They are very reactiveD
They are bigger in sizeClick an option to check your answer
Q. 36
How many atoms of oxygen are present in 300 grams of CaCO₃?
A
54.207 × 10²³B
22.2 × 10²³C
6.207 × 10²³D
12.207 × 10²³Click an option to check your answer
Q. 37
Study of internal structure of Earth is known as
A
nuclear physicsB
geophysicsC
atomic physicsD
mechanicsClick an option to check your answer
Q. 38
3.42 g of sucrose are dissolved in 18 g of water. The number of oxygen atoms in the solution is:
A
6.68 × 10²³B
6.09 × 10²²C
6.022 × 10²¹D
6.022 × 10²³Click an option to check your answer
Q. 39
How many atoms are in a molecule of phosphorus (P₄)?
A
4B
1C
8D
2Click an option to check your answer
Q. 40
The reaction used to verify the law of conservation of mass is included in which category?
A
Precipitation reactionB
Double displacement reactionC
Neutralization reactionD
Both Precipitation reaction and Double displacement reactionClick an option to check your answer
Q. 41
Which statement is not in accordance with Dalton’s atomic theory?
A
All matter is made of tiny particles.B
Atoms can be divided into subatomic particles.C
Atoms of given elements are identical in mass and properties.D
Atoms combine in small whole number ratios.Click an option to check your answer
Q. 42
What is a molecule?
A
A single atomB
A group of atomsC
A compoundD
A charged ionClick an option to check your answer
Q. 43
An element X is divalent and another element Y is tetravalent. The compound formed will be:
A
XY₂B
XY₄C
XYD
X₂YClick an option to check your answer
Q. 44
Which element has an atomic mass closest to 12 u?
A
NitrogenB
HydrogenC
CarbonD
OxygenClick an option to check your answer
Q. 45
How is the molecular mass of a substance expressed?
A
In gramsB
In litersC
In atomic mass unitsD
In molesClick an option to check your answer
Q. 46
What is the formula mass unit of ZnO?
A
18 uB
88 uC
81 uD
188 uClick an option to check your answer
Q. 47
What do the subscripts in a chemical formula represent?
A
Number of ionsB
Number of moleculesC
Number of atomsD
Number of elementsClick an option to check your answer
Q. 48
When CaCO3 is heated, it forms CaO and CO2. What best describes the mass of products?
A
The mass of each product is equal to CaCO3.B
The sum of the products’ masses equals the mass of CaCO3.C
The sum of the products’ masses is less than the mass of CaCO3.D
The difference in products’ masses is equal to the mass of CaCO3.Click an option to check your answer
Q. 49
Which constituent of air is monoatomic?
A
Water vapourB
ArgonC
OxygenD
NitrogenClick an option to check your answer
Q. 50
What is the atomic mass of nitrogen?
A
14 a.m.u.B
7 a.m.u.C
8 a.m.u.D
16 a.m.u.Click an option to check your answer
Q. 51
Which of the following is a polyatomic ion?
A
Cl⁻B
H₂C
OH⁻D
Na⁺Click an option to check your answer
Q. 52
Which statement is true about the law of conservation of mass?
A
Elements are always present in a constant proportion.B
If two elements form more than one compound...C
The rate of reaction is proportional to active mass.D
In a chemical reaction, matter is conserved.Click an option to check your answer
Q. 53
What is a major drawback of Dalton’s atomic theory?
A
Atoms of an element have exactly the same mass.B
All of theseC
Atoms of different elements have same masses.D
Atoms are indivisible.Click an option to check your answer
Q. 54
A change in the physical state can be brought about:
A
only when energy is given to the systemB
Without any energy changeC
only when energy is taken out from the systemD
When energy is either given to or taken outClick an option to check your answer
Q. 55
What is the atomic mass unit (amu) based on?
A
OxygenB
Carbon-12C
NitrogenD
HydrogenClick an option to check your answer
Q. 56
Valency of Calcium element is:
A
5B
4C
2D
3Click an option to check your answer
Q. 57
Which of the following is a triatomic molecule?
A
O₃B
Cl₂C
H₂D
N₂Click an option to check your answer
Q. 58
The molecular formula of potassium nitrate is ________.
A
KNOB
KNO₂C
KNO3D
KONClick an option to check your answer
Q. 59
What type of molecule is helium (He)?
A
MonoatomicB
DiatomicC
PolyatomicD
TriatomicClick an option to check your answer
Q. 60
Which statement about atoms is correct?
A
They cannot bondB
They are visibleC
They always form moleculesD
They can exist independentlyClick an option to check your answer
Q. 61
Molecular mass is defined as the:
A
Mass of one molecule compared to one atom of C-12B
Mass of one atom compared to the mass of one atom of hydrogenC
Mass of one atom compared to one moleculeD
None of the aboveClick an option to check your answer
Q. 62
The atomic masses and chemical properties of Sulphur and Phosphorus are different. This can be explained on the basis of:
A
Law of constant proportionsB
Dalton’s Atomic theoryC
Law of conservation of massD
Laws of Chemical combinationClick an option to check your answer
Q. 63
What is the valency of an element?
A
Its colorB
Its atomic massC
Its ability to combineD
Its chargeClick an option to check your answer
Q. 64
Who proposed the Law of Constant Proportions?
A
Antoine LavoisierB
Joseph ProustC
John DaltonD
Dmitri MendeleevClick an option to check your answer
Q. 65
According to Law of conservation of mass, mass of reactants will be equal to the mass of:
A
Apparatus used for reactionB
Gases evolvedC
CatalystsD
ProductsClick an option to check your answer
Q. 66
What is the formula unit mass of CaCl₂?
A
150 uB
71 uC
100 uD
111 uClick an option to check your answer
Q. 67
The number of atoms present in one molecule of an element is called as:
A
AtomicityB
MoleculeC
Empirical formulaD
CompoundClick an option to check your answer
Q. 68
What does a cation represent?
A
Neutral ionB
Negatively charged ionC
Positively charged ionD
A group of atomsClick an option to check your answer
Q. 69
Molecules of compounds are made up of different types of atoms in ______ proportions.
A
definiteB
specificC
unlimitedD
randomClick an option to check your answer
Q. 70
A sample of NH3 molecule contains 82.35% Nitrogen and 17.65% Hydrogen by mass. This data supports:
A
Law of Definite ProportionsB
Law of Conservation of MassC
Avogadro’s LawD
Law of Multiple ProportionsClick an option to check your answer
Q. 71
What is the molecular mass of water (H₂O)?
A
20 uB
16 uC
12 uD
18 uClick an option to check your answer
Q. 72
How are formulas for compounds with polyatomic ions written?
A
With numbersB
With bracketsC
With no bracketsD
With lettersClick an option to check your answer
Q. 73
Which of the following is a diatomic molecule?
A
H₂OB
N₂C
O₃D
CO₂Click an option to check your answer
Q. 74
Maharishi Kanad suggested that matter could be divided until reaching an indivisible unit called "_____".
A
ParmanusB
ProtonsC
AtomsD
MoleculesClick an option to check your answer
Q. 75
Which of the following represents a correct chemical formula?
A
NaSB
CaClC
NaSO₄D
BiPO₄Click an option to check your answer
Q. 76
What is a negatively charged ion called?
A
CationB
AnionC
ProtonD
NeutronClick an option to check your answer
Q. 77
5 grams of compound A reacts with 10 grams of compound B... What should be the mass of C?
A
50 gB
15 gC
10 gD
5 gClick an option to check your answer
Q. 78
NaCl molecule is made of which of the following ions?
A
Na cation and Cl anionB
Cl cation and Na anionC
Both Na and Cl cationD
Both Na and Cl anionClick an option to check your answer
Q. 79
Which one of the following is the modern symbol of Gold?
A
GlB
GoC
SiD
AuClick an option to check your answer
Q. 80
Which is correct for the ‘Law of Conservation of Mass’?
A
Mass can be created or destroyed.B
The rate of reaction is directly proportional to active mass.C
Mass can neither be created nor destroyed.D
Elements are always present in a constant proportion.Click an option to check your answer
Q. 81
What does the Law of Conservation of Mass state?
A
Mass can be createdB
Mass changes in reactionsC
Mass remains constantD
Mass can be destroyedClick an option to check your answer
Q. 82
Who stated the Law of conservation of mass?
A
ThomsonB
DaltonC
CavendishD
LavoisierClick an option to check your answer
Q. 83
What should be the formula of hydrogen sulphide?
A
H2S2B
H2SC
HSD
HS2Click an option to check your answer
Q. 84
Which of the following is a characteristic of a molecule?
A
Cannot exist aloneB
Cannot form bondsC
Is visibleD
Has fixed massClick an option to check your answer
Q. 85
An atom has a mass number of 23 and atomic number 11. The number of protons are ________.
A
11B
23C
12D
44Click an option to check your answer
Q. 86
Which is not a postulate of Dalton’s atomic theory?
A
The number of atoms in a compound is fixed.B
Atoms cannot be divided.C
Atoms can neither be created nor destroyed.D
Atoms of the same elements cannot combine in more than one ratio.Click an option to check your answer
Q. 87
If all reactants in a chemical reaction are completely used, which statement accurately describes the relationship?
A
Products must have different physical states than reactants.B
Total mass of reactants = total mass of products.C
Density of reactants must equal density of products.D
Reactants must contain more complex molecules than products.Click an option to check your answer
Q. 88
Chemical formula of a compound is A2B3. The valency of A is
A
5B
6C
3D
2Click an option to check your answer
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