MCQ Questions for Class 9 Chemistry Atoms And Molecules Quiz 1

Who called the indivisible particles as atoms?

0%
Antoine L. Lavoisier
0%
Democritus
0%
Rutherford
0%
Both B and C

Explanation

$430 \ B.C$ , Democritus postulated that matter is made up of very small particles called “atoms” which means"indivisible".

________ is the latin name for sodium.

0%
Sodiumin
0%
Natrium
0%
Natrimium
0%
Kalium

Explanation

The chemical abbreviation for sodium atom is

$Na,$ from its Latin name,

$Natrium$ .

When did Maharishi Kanad give the idea of parmanu ?

0%
$500 BC$
0%
$100 BC$
0%
$460 BC$
0%
$1808 BC$

What is atomic mass of

$He$ in amu

$(u)$ units?

0%
$8$
0%
$9$
0%
$2$
0%
$4$

Explanation

The atomic mass of an element is the average mass of an element measured in an atomic mass unit (amu). The atomic mass of

$He$ is

$4\ u$ .

Option

$D$ is correct.

The cation in

$CaCl_2$ is:

0%
$Ca^{+}$
0%
$Cl^{2-}$
0%
$Ca^{2+}$
0%
$Cl^{2+}$

Explanation

$CaCl_2$ is made up of

$Ca^{2+}$ and

$2Cl^-$ .

A cation contains is a positively charged ion, so the cation in

$CaCl_2$ is

$Ca^{2+}$

The term mole is a latin word which means:

0%
bunch
0%
heap or pile
0%
herd
0%
flock

Avogadro number is equal to:

0%
$6.023\times10^{21}$
0%
$6.023\times10^{22}$
0%
$6.023\times10^{23}$
0%
$6.023\times10^{24}$

One mole is defined as:

0%
quantity having a mass equal to its atomic/molecular mass.
0%
quantity having mass equal to half of its atomic/molecular mass.
0%
one gram of any quantity.
0%
one kilogram of any quantity.

Explanation

One mole is defined as a quantity having a mass equal to its atomic/molecular mass.

For example, one mole sodium

$(Na) = 23 \ gm =$ atomic mass of sodium

Which of the following property of an element never changes?

0%
Valency
0%
Atomic weight
0%
Both A and B
0%
None of the above

Cation and anion present (if any) in NaCl is :

0%
Anion: $Cl^{2-}$ Cation: $Na^+$
0%
Anion: $Cl^{-}$ Cation: $Na^{2+}$
0%
Cation: $Cl^{-}$ Anion: $Na^+$
0%
Anion: $Cl^{-}$ Cation: $Na^+$

Explanation

Separate the compound into its cation and anion.

$NaCl \rightarrow Na^+ + Cl^-$
Cation

$\rightarrow Na^+$
Anion

$\rightarrow Cl^-$

Avogadro's number is the number of molecules present in:

0%
1 g of molecule
0%
1 atom of molecule
0%
1 mole
0%
1 litre of molecule

Explanation

The Avogadro constant is defined as the number of constituent particles per mole of a given substance. It is equal to

$6.022\times 10^{23}$ .

Calculate the molecular mass of the lime stone.

0%
$CaCO_2 = 84 g mol^{-1}$
0%
$CaCO_3 = 100 g mol^{-1}$
0%
$Ca_2CO_3 = 140 g mol^{-1}$
0%
$CaCO = 68 g mol^{-1}$

Explanation

Formula for lime stone is

$CaCO_3$ . Molar mass

$= 40 + 12 + (3 \times 16) = 100 g mol^{-1}$

Cations and anions present (if any) in

$H_2$ are:

0%
$H^+$
0%
$H^-$
0%
$H^{2+}$
0%
None of the above

Explanation

$H_2$ molecule is formed by covalent bond and hence, it does not have any cations and anions.

The value of 1 amu is equal to:

0%
$1.66\times 10^{-8}g$
0%
$1.66\times 10^{-4}g$
0%
$1.66\times 10^{-16}g$
0%
$1.66\times 10^{-24}g$

Explanation

One an amu is

$\dfrac{1}{12}$ of the mass of one carbon-12 atom.

It is equal to

$\dfrac{1}{N_A}$

$= \dfrac{1}{6.022\times10^{23}} = 1.66 \times 10^{-24} g$ .

The formula and molecular mass of caustic soda is :

0%
$NaOH = 40 g mol^{-1}$
0%
$Na_2OH = 63 g mol^{-1}$
0%
$Na(OH)_2 = 57 g mol^{-1}$
0%
none of the above

Explanation

Sodium has valency

$+1$ and is represented as

$Na,$ and hydroxyl has a valency of

$-1$ and is represented as

$OH^-$ . Caustic soda is

$NaOH.$ Molar mass =

$23+16+1 = 40 g mol^{-1}$ .

Calculate the molecular mass of the baking powder.

0%
$NaHCO_2 = 68 g mol^{1}$
0%
$Na_2HCO_3 = 107 g mol^{1}$
0%
$NaHCO_3 = 84 g mol^{1}$
0%
none of these

Explanation

Baking powder (sodium bicarbonate) -

$NaHCO_3$
Molar mass -

$23 + 1 + 12 + (3 \times 16) = 84 g mol^{-1}$

The % of Copper and Oxygen in samples of CuO obtained by different methods were found to be the same.

This proves the law of:

0%
constant proportions
0%
reciprocal proportions
0%
multiple proportions
0%
conservation of mass.

Which of the following is used as standard for determination of atomic mass unit?

0%
$O^{16}$
0%
$C^{12}$
0%
$H^{1}$
0%
$O^{17}$

Explanation

Atomic mass of a compound is measured in atomic mass units abbreviated as amu or u. One atomic mass unit is defined as

$\frac{1}{12}^{th}$ of mass of a single carbon-12 atom.

A negatively charged ion is known as anion.

0%
True
0%
False

Explanation

$(A)$

$True$

$Reason$ : A negatively charged ion is known as an anion, as an anion is formed by the gain of one or more electrons by an atom.

$Example$ : Chlorine gains one electron to form chloride ion

$(Cl^-)$ .

Which one of the following properties of an element is not variable?

0%
Valency
0%
Atomic weight
0%
Equivalent weight
0%
All of these

The element lead is derived from the Latin name plumbum.

0%
True
0%
False

Explanation

Lead's chemical symbol

$Pb$ comes from the Latin word 'plumbum'.

The symbols of lead and mercury are respectively:

0%
$Hg, Pb$
0%
$Pb, Hg$
0%
$Le,Me$
0%
$Ld, My$

Explanation

Symbol of lead is

$Pb$ and of mercury is

$Hg$
Therefore option B is correct.

A molecule is made up of like atoms.

0%
True
0%
False

Explanation

A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Atoms may be same or different varies in molecules.

Example :

$H_2, CO_2$ etc.

A symbol of an element is always represented by the first alphabet of an atom of the element.

0%
True
0%
False

Explanation

The statement is not true. For example, symbol for tin is

$Sn$ , tungsten is

$W$ , potassium is

$K$ , sodium is

$Na$ and there are several other examples. Some symbols of elements have been taken from their Greek names, Latin names, and sometimes even their colours.

A balanced chemical equation is in accordance with the law of conservation of mass.

0%
True
0%
False

Explanation

A balanced chemical equation is an equation in which the number of atoms of reactants and products taking part in the reaction is equal.
The law of conservation of mass states that an atom can neither be created nor be destroyed but can be transformed from one form to the other.

According to the law, the mass of reactants

$=$ mass of products i.e. atoms of reactants are rearranged to form products, and the total amount of mass in the chemical equation remains constant. Hence the given statement is true.

Number of atoms in

$12$ gm of

$^{12}_6C$ is:

0%
$6$
0%
$12$
0%
$6.02\times 10^{23}$
0%
$6\times 6.02\times 10^{23}$

Explanation

The Avogadro number, which is

$6.022 \times 10^{23}$ is defined as the number of atoms in exactly 12 g of

$^{12}_6C$ (carbon-12). So, we can say that the number of atoms in 12 gm of carbon-12 is

$6.022 \times 10^{23}$ .

The value of the Avogadro constant is :

0%
$6.022\times 10^{24}$
0%
$6.022\times 10^{22}$
0%
$60.22\times 10^{24}$
0%
$6.022\times 10^{23}$

Explanation

Correct option : $D$

Explanation:

Avogadro constant is defined as the number of constituent particles per mole of a given substance.
The value for Avogadro's constant is $6.022 \times 10^{23}$ .
It is used as the number of units in a mole of any substance.
For Example: 1 mole of $CO_2$ has $44 \ g$ and it has $6.022 \times 10^{23}$ molecules in it.

Mass of one twelth of carbon atom is called atomic mass unit.

0%
True
0%
False

Explanation

An atomic mass unit(amu) is defined as

$\frac{1}{12}^{th}$ the mass of an atom of

$C-12$

The relative atomic masses of all elements have been found with respect to an atom of carbon-12.

_________ is the smallest unit of matter which may or may not have an independent existence, but always takes part in a chemical reaction.

0%
An Atom
0%
A compound
0%
A crystal
0%
All the above

Explanation

An atom is the smallest unit of matter which takes part in a chemical reaction, it may or may not have an independent existence.

A compound is formed by definite composition of atoms. Example- Water (

$H_2O$ )- there are 2 Hydrogen atoms and 1 oxygen atom.

A crystal is a periodic arrangement of atoms or ions. Example- Cu, NaCl

Molecular weight of water is

$20$ u.

0%
True
0%
False

Explanation

Molecular formula of water is

$H_2O$
Atomic weight of

$H$ is

$1$ u and of

$O$ is

$16$ u
Molecular weight of water =

$2\times mass\ of\ H+1\times mass\ of\ O$

$2\times 1 + 16=18$ u
Therefore, option

$B$ is correct.

The molecular mass of

$(NH_2)_2CO$ is :

(Given atomic mass of H = 1, O = 16, C = 12, N = 14.)

0%
$90gm/mole$
0%
$80gm/mole$
0%
$60gm/mole$
0%
$62gm/mole$

Explanation

Molar mass

$(NH_2)_2CO = 2 \times (14+2)+12+16 = 60 gm/mole$

A symbol of an element does not convey information about:

0%
Atomic number
0%
Atomic weight
0%
Mass number
0%
All of the above

Explanation

Each element of the periodic table has a one, two or three letter unique symbol, which is an abbreviated form of its present or old name. It does not convey about its elemental properties like atomic number, atomic weight or mass number.
Therefore option

$D$ is correct.

An atom is different from its ion in:

0%
nuclear charge
0%
mass number
0%
number of electrons
0%
number of neutrons

Explanation

An ion is formed by gain or loss of electrons from a neutral atom. The number of electrons gained or losses is the charge of that ion. Therefore an atom and an ion differ in the number of electrons.

Hence, the correct option is

$C$ .

The molecular mass of

$Mg_3N_2$ is ::

Given atomic mass of

$(N = 14, Mg = 24.)$

0%
$84gm/mole$
0%
$98gm/mole$
0%
$114gm/mole$
0%
$100gm/mole$

Explanation

Molar mass

$Mg_3N_2 = 3\times24+2\times14 = 100 gm/mole$

What is the representation of atom of hydrogen and a molecule of hydrogen?

0%
$H$ and $H_2$
0%
$H_2$ and $H$
0%
$H$ and $H$
0%
$H_2$ and $H_2$

Explanation

The hydrogen atom is written as

$H$ and hydrogen molecule is formed by the combination of two hydrogen atoms and is written as

$H_{2}$ .

The statement "atom is indivisible" was proposed by:

0%
Rutherford
0%
Dalton
0%
Bohr
0%
Einstein

The chemical formula of a particular compound represents:

0%
the size of molecule
0%
the shape of its molecules
0%
the total number of molecules in the compound
0%
the number of different types of atoms in its molecule

Explanation

The chemical formula of a particular compound represents the number of different types of atoms in its molecule. For instance, the compound

$CO_2$ (carbon dioxide) has one carbon atom and two oxygen atoms. It does not represent the size or shape of the molecule or the number of molecules in the compound.

Which is the smallest possible unit of a chemical compound?

0%
Atom
0%
Electron
0%
Proton
0%
Molecule

Law of constant composition is also called as the law of :

0%
Conservation of mass
0%
Conservation of energy
0%
Multiple proportion
0%
Definite proportion

A 'mole' of a substance is the same as ________.

0%
avogadro's number of particles of the substance
0%
the molecule
0%
the quantity of substance reacting with 8 parts of oxygen
0%
the saturated solution of the substance

Explanation

The mole is a unit of measurement for amount of substance. It is defined as the amount of any chemical substance that contains elementary particles e.g. atoms,molecules,ions or electrons. This number is expressed by the Avogadro constant which has value of

${ 6.022\times10 }^{ 23 }$ .

The amount of a chemical substance is reported as _______.

0%
mole
0%
mass
0%
volume
0%
density

Explanation

Mole

$= \dfrac {Given \ mass \ of \ a \ substance}{Molecular \ mass \ or \ atomic \ mass}$

Which is the lightest element in the universe?

0%
Helium
0%
Hydrogen
0%
Nitrogen
0%
Silicon

Explanation

$\text {Hydrogen}$ is the lightest element in the universe with atomic number

$1$ and so, it has the simplest atomic structure.

Which of the following represents Plumbous ion?

0%
$Pb^{+2}$
0%
$Pb^{+4}$
0%
$Pb^{+3}$
0%
$Pb^{+1}$

Explanation

Lead looses 2 electrons when combines with other element.

So Plumbous ion is written as;

$Pb^{2+}$ .

The atomic theory of matter was proposed by :

0%
John Kennedy
0%
Lavoisier
0%
Proust
0%
John Dalton

Avogadro's number represents the number of atoms in:

0%
12 g of $C^{12}$
0%
320 g of sulphur
0%
32 g of oxygen
0%
14.3 of sulphur

Explanation

Avogadro's number represents the number of atoms in 12 g of

$C^{12}$

The smallest unit of a compound is called a molecule.

0%
True
0%
False

The mass number of sulfur atom is:

(Given: Atomic number = 16 and number of neutrons = 16)

0%
18
0%
32
0%
24
0%
16

Explanation

Atomic number = number of protons =

$16$

Mass number = Number of protons + number of neutrons

So the mass number of sulfur =

$32$

Mass of atom expressed in atomic mass unit is :

0%
Atomic mass
0%
Molecular mass
0%
Atomic number
0%
None of the above

What is the atomic mass (u) of calcium?

0%
10
0%
20
0%
30
0%
40

Explanation

Atomic mass (u) of Calcium is 40 u.

Hence, the correct option is

$\text{D}$

One a.m.u is defined as mass of :

0%
$\frac{1}{16}^{th}$ mass of one oxygen atom
0%
$\frac{1}{14}^{th}$ mass of one atom of nitrogen
0%
$\frac{1}{12}^{th}$ mass of one carbon-12 atom
0%
None of above

Explanation

One a.m.u. is defined as mass of

$\frac1{12}^{th}$ the mass of one carbon-12 atom.

CBSE Questions for Class 9 Chemistry Atoms And Molecules Quiz 1 - MCQExams.com

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Practice Class 9 Chemistry Quiz Questions and Answers

CBSE Questions for Class 9 Chemistry Atoms And Molecules Quiz 1 - MCQExams.com

0:0:1

Practice Class 9 Chemistry Quiz Questions and Answers

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