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Science M.C.Q. [1 M]

Atoms and Molecules · Gujarat Board (GSEB) STD 9 (GSEB - English Medium). 182 questions.

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M.C.Q. [1 M]

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MCQ 11 Mark
Protons and neutrons clump together to form the __________ of an atom.
  • A
    Nucleus
  • B
    Centrosome
  • C
    Outer shell
  • D
    Orbital
Answer
  1. Nucleus
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MCQ 21 Mark
Arrange the following according to correct Dalton's symbols. Hydrogen Carbon Oxygen Sulphur:
  • A
    $\text{Hydrogen}\bullet\text{Carbon}\odot\text{Oxygen}\oplus\text{Sulphus}\bigcirc$
  • B
    $\text{Hydrogen}\odot\text{Carbon}\bullet\text{Oxygen}\bigcirc\text{Sulphus}\oplus$
  • C
    $\text{Hydrogen}\bigcirc\text{Carbon}\odot\text{Oxygen}\bullet\text{Sulphus}\oplus$
  • D
    $\text{Hydrogen}\oplus\text{Carbon}\bigcirc\text{Oxygen}\odot\text{Sulphus}\bullet$
Answer
  1. $\text{Hydrogen}\bigcirc\text{Carbon}\odot\text{Oxygen}\bullet\text{Sulphus}\oplus$
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MCQ 31 Mark
1.008 grams of hydrogen combines with 35.453 g of chlorine to form 36.463 g of a pure compound (hydrogen chloride). Dalton's explanation for this experimental fact might be: 
  • A
    One atom of hydrogen combines with 35.453 atoms of chlorine in this reaction
  • B
    Hydrogen and chlorine atoms always combine in a 1:35 ratio.
  • C
    Chlorine accepts hydrogen's electron to form polar covalent hydrogen chloride
  • D
    Hydrogen and chlorine atoms aren't created or destroyed in the process so the reactant mass is the same as the product mass.
Answer
  1. Hydrogen and chlorine atoms aren't created or destroyed in the process so the reactant mass is the same as the product mass.

Explanation:

Dalton Atomic theory postulates-

All matter is made up of atoms and atoms are indestructible cannot be created or destroyed so the total mass of reactants remains equal to the total mass of products.

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MCQ 61 Mark
Which part of an atom is represented by the blue circles?
  • A
    Electrons
  • B
    Neutrons
  • C
    Protons
  • D
    A and B
Answer
  1. Electrons
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MCQ 81 Mark
Which of the following represents a correct chemical formula?
  • A
    CaCl
  • B
    Na3N
  • C
    NaSO4
  • D
    NaS
Answer
  1. Na3N

Explanation:

The correct chemical formula among the listed chemicals is of Na3N.

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MCQ 91 Mark
The chemical symbol for sodium is:
  • A
    So
  • B
    Sd
  • C
    NA
  • D
    Na
Answer

  1. NA

Explanation:

Name "sodium" has been derived from Latin - natrium.

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MCQ 101 Mark
The law of constant proportions was given by:
  • A
    Proust.
  • B
    Lavoisier.
  • C
    Dalton.
  • D
    Berzelius.
Answer
  1. Proust.

Explanation:

The law of constant proportion was proposed by Joseph Proust.

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MCQ 111 Mark
The formula of a compound is X3Y. The valencies of elements X and Y will be respectively:
  • A
    1 and 3
  • B
    3 and 1
  • C
    2 and 3
  • D
    3 and 2
Answer
  1. 1 and 3

Explanation:

Valencies of element X and Y will be 1 and 3, respectively.

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MCQ 121 Mark
'All matter is composed of very small particles called Parmanu' was first suggested by:
  • A
    John Dalton
  • B
    J.J. Thomson
  • C
    Kanad
  • D
    William J. Crooke
Answer
  1. Kanad

Explanation:

Indian philosopher who suggested that all matter is composed of very small particles was Maharshi Kanad.

The particles were called Parmanu (atom).

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MCQ 131 Mark
Which of the following is not a postulate of Dalton's atomic theory
  • A
    Different elements have atoms of different masses.
  • B
    Atoms combine in simple whole number ratios to form compounds.
  • C
    Atoms are not created or destroyed in chemical change.
  • D
    Atoms of a single element can have different masses.
Answer
  1. Atoms of a single element can have different masses

Explanation:

Postulates of Dalton's atomic theory:

All matter consists of indivisible particles called atoms.

Atoms of the same elements are similar in shape and mass but differ from the atoms of other elements.

Atoms cannot be created or destroyed.

Atoms of different elements may combine with each other in fixed, simple, whole-number ratios to form elements and compounds.

The atom is the smallest unit of matter that can take part in a chemical reaction.

'Atoms of a single element can have different masses' is not present in postulates of Dalton's atomic theory.

It is in fact a limitation of Dalton's atomic theory

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MCQ 141 Mark
‘X’ and ‘Y' are two elements which form X2Y3 and X3Y4. If 0.2mol of X2Y3 weighs 32g and 0.4mol of X3Y4, weighs 92.8g, the atomic weights of X and Y respectively are:
  • A
    16, 56
  • B
    16, 16
  • C
    56, 16
  • D
    56, 56
Answer
  1. 56, 16

Explanation:

Molecular weight of X2Y3 = 32.0g/0.2mol

X2Y3 = 32.0g/0.2mol = 160g/mol

Molecular weight of X3Y4 = 92.8g/0.4mol

X3Y4 = 92.8g/0.4mol = 232g/mol

Now suppose the atomic weight of X = a and atomic weight of Y = b

Then, 2a + 3b = 160 ......(i)

And, 3a + 4b = 232 ......(ii)

For equ (i)

$\text{A}=\frac{(160-3\text{b})}{2}$

Put value of (i) in (ii)

$3\frac{(160-3\text{b})}{2}+4\text{b}=232$

After solving,

a = 56 and b = 16

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MCQ 151 Mark
Avogadro number is the number of atoms present in exactly:
  • A
    16g of oxygen
  • B
    12g of carbon
  • C
    2g of hydrogen
  • D
    None of the above
Answer
  1. 12g of carbon

Explanation:

Avogadro number is the number of atoms in exactly 12g of carbon -12.

It is equal to 6.022×1023.

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MCQ 161 Mark
16g of S8 molecules contain:
  • A
    3.78 × 1022 atoms.
  • B
    3.78 × 1022 × 8 atoms.
  • C
    3.78 × 1022 moles.
  • D
    3.78 × 1023 molecules.
Answer
  1. 3.78 × 1023 molecules.

Explanation:

Molar mass of S8 = 256g mol-1

We know,

1 mole of S8 = Molar mass of S8 = 6.022 × 1023 molecules.

256g of S8 = 6.022 × 1023 molecules.

Hence, 16g of S8 $=\frac{6.022\times10^{23\times}16}{256}$ molecules

= 3.76 × 1022 molecules

= 3.76 × 1022 molecules

= 3.78 × 1023 molecules (approx)

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MCQ 171 Mark
Which of the following symbol of elements is not taken from Latin names:
  • A
    K
  • B
    Na
  • C
    Cu
  • D
    Zn
Answer
  1. Zn

Explanation:

K, Na, Cu is derived from Latin names namely Kalium, Natrium, and Cuprum.

The symbol of Zinc is not taken from Latin names.

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MCQ 181 Mark
The Latin language name of an element is natrium. The English name of this element is:
  • A
    Sodium.
  • B
    Potassium.
  • C
    Magnesium.
  • D
    Sulphur.
Answer
  1. Sodium.

Explanation:

The English name of the element natrium is Sodium(Na).

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MCQ 191 Mark
The atoms of which of the following pair of elements are most likely to exist in free state?
  • A
    Hydrogen and helium.
  • B
    Argon and carbon.
  • C
    Neon and nitrogen.
  • D
    Helium and neon.
Answer
  1. Helium and neon.

Explanation:

Atoms of helium and neon exist in a free state because they are inert gases and chemically inactive.

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MCQ 221 Mark
An ionic compound will be formed by the combination of one of the following pairs of elements. This pair of elements is:
  • A
    Chlorine and calcium.
  • B
    Calcium and sodium.
  • C
    Sulphur and carbon.
  • D
    Chlorine and chlorine.
Answer
  1. Chlorine and calcium.

Explanation:

Chlorine and calcium can form an ionic compound CaCl2.

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MCQ 231 Mark
A solution of copper oxide was prepared by heating, igniting and precipitation. Which of the following method will give higher ratio of copper oxide:
  • A
    Heating
  • B
    Precipitation
  • C
    Ignition
  • D
    All of the above will give the same ratio
Answer
  1. All of the above will give the same ratio

Explanation:

In a compound, the ratio of the atoms or element by mass remains always the same irrespective of the source of the compound.

This means a certain compound is always formed by the combination of atoms in the same ratio by mass.

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MCQ 241 Mark
A student wants to have 3.011 × 1023 atoms each of magnesium and carbon elements. For this purpose, he will have to weigh:
  • A
    24g of magnesium and 6g of carbon.
  • B
    12g of carbon and 24g of magnesium.
  • C
    20g of magnesium and 10g of carbon.
  • D
    12g of magnesium and 6g of carbon.
Answer
  1. 12g of magnesium and 6g of carbon.

Explanation:

The student will have to weigh 12g of Magnesium and 6g of Carbon.

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MCQ 251 Mark
In ammonia, nitrogen and hydrogen always combine in 14 : 3 ratio by mass.This is in agreement with:
  • A
    Law of conservation of mass
  • B
    Law of definite proportion
  • C
    Law of multiple proportion
  • D
    Law of combining volume
Answer
  1. Law of definite proportion
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MCQ 261 Mark
The scientist who proposed the first letter (or first letter and another letter) of the Latin or English name of an element as its symbol, was:
  • A
    Dalton.
  • B
    Proust.
  • C
    Lavoisier.
  • D
    Berzelius.
Answer
  1. Berzelius.

Explanation:

Berzelius proposed the first letter (or first letter and another letter) of the Latin or English name of any element as its symbol.

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MCQ 271 Mark
The English name of an element is potassium, its Latin name will be:
  • A
    Plumbum.
  • B
    Cuprum.
  • C
    Kalium.
  • D
    Natrium.
Answer
  1. Kalium.

Explanation:

The Latin name of the element potassium is kalium. Hence, the symbol for potassium is K.

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MCQ 281 Mark
The atomic number of an element X is 13. What will be the number of electrons in its ion X3+?
  • A
    11
  • B
    15
  • C
    16
  • D
    10
Answer
  1. 10

Explanation:

If the atomic number of X is 13, the number of electrons in its X3+ ion would be 13 - 3 = 10.

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MCQ 291 Mark
Which of the following pair of elements represents a mole ratio of 1 : 1?
  • A
    10g of calcium and 12g of magnesium.
  • B
    12g of magnesium and 6g of carbon.
  • C
    12g of carbon and 20g of calcium.
  • D
    20g of sodium and 20g of calcium.
Answer
  1. 12g of magnesium and 6g of carbon.

Explanation:

12g of magnesium and 6g of carbon will have a mole ratio of 1 : 1

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MCQ 311 Mark
Smallest particle of an element or a compound which is capable of independent existence is called:
  • A
    Atom
  • B
    Molecule
  • C
    Element
  • D
    Compound
Answer
  1. Molecule

Explanation:

Smallest particle of an element or a compound which is capable of independent existence is called molecule.A molecule is formed when two or more atoms join together chemically.

Molecules of elements like noble gases such as helium,neon etc are made up of one atom only(molecules are capable of independent existence while atoms are not capable of independent existence).

Only in these case atoms are capable of independent existence.

Noble gases are monoatomic.

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MCQ 321 Mark
Which of the following is not a property of a molecule?
  • A
    Molecules of any given substance are similar.
  • B
    Molecules are represented by chemical formula.
  • C
    The properties of a substance are the properties of the molecule.
  • D
    None of above.
Answer
  1. None of above.
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MCQ 331 Mark
The atomic theory of matter was proposed by:
  • A
    John Kennedy.
  • B
    Lavoisier.
  • C
    Proust.
  • D
    John Dalton.
Answer
  1. John Dalton.

Explanation:

The atomic theory of matter was proposed by John Dalton.

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MCQ 361 Mark
The atomic radius of hydrogen is in nanometers:
  • A
    37nm
  • B
    0.37nm
  • C
    0.037nm
  • D
    0.0037nm
Answer
  1. 0.037nm

Explanation:

Element Symbol Atomic number Atomic radius in nanometers
Hydrogen H 1 0.037
Helium He 2 0.05
Lithium Li 3 0.152
Beryllium Be 4 0.111
Boron B 5 0.088
Carbon C 6 0.077
Nitrogen N 7 0.070
Oxygen O 8 0.066
Fluorine F 9 0.064
Neon Ne 10 0.070
Sodium Na 11 0.186
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MCQ 371 Mark
Four students A, B, C and D verified the law of conservation of mass by performing chemical reaction between barium chloride and sodium sulphate. All of them took 107.2g barium chloride solution and 116.1g of sodium sulphate solution and mixed them in the beaker of mass 150g. They reported their results as follows:
Students
Colour of reaction mixture after mixing
Mass of reation mixture in the beaker including mass of beaker
A
White Precipitate
383.3g
B
Brown Precipitate
393.3g
C
White Precipitate
373.3g
D
Brown Precipitate
363.3g
The correct observation is that of student.
  • A
    A.
  • B
    B.
  • C
    C.
  • D
    D.
Answer
  1. C

Explanation:

Mass of barium sulphate =107.2g

Mass of barium chloride = 116.g

Mass of beaker = 150g

Total mass of reaction mixture in the beaker including mass of

Beaker = 107.2g + 116.1g + 150g = 373.3g

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MCQ 381 Mark
If the number of electrons in an ion Z3- is 10, the atomic number of element Z will be:
  • A
    7
  • B
    5
  • C
    10
  • D
    8
Answer
  1. 7

Explanation:

If the number of electrons in an ion Z3- is 10, the atomic number of element Z will be 7 because the ion is formed by gaining three electrons.

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MCQ 391 Mark
If the ratio of the atoms by mass is altered then:
  • A
    New compound formed
  • B
    Same compounds are formed
  • C
    No reaction takes place
  • D
    State of compounds are changed
Answer
  1. New compound formed

Explanation:

In a compound, the ratio of the atoms or element by mass remains always the same irrespective of the source of the compound.

This means a certain compound is always formed by the combination of atoms in the same ratio by mass.

If the ratio of the mass of constituent atoms will be altered the new compound is formed.

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MCQ 401 Mark
Which scientist proposed the concept of atomic mass:
  • A
    Avogadro
  • B
    Gay Lussac
  • C
    Proust
  • D
    Dalton
Answer
  1. Proust

Explanation:

The concept of atomic mass was proposed by William Prout.

Early atomic mass theory was proposed by the English chemist William Prout in a series of published papers in 1815 and 1816.

Known as Prout's Law, Prout suggested that the known elements had atomic weights that were whole number multiples of the atomic mass of hydrogen.

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MCQ 411 Mark
Which of the following is not correctly matched ?
  • A
    Calcium - Ca
  • B
    Silver - Ag
  • C
    Gold - Au
  • D
    Copper - Co
Answer
  1. Copper - Co
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MCQ 421 Mark
The ratio of moles of atoms in 12g of magnesium and 16g of sulphur will be:
  • A
    3 : 4
  • B
    4 : 3
  • C
    1 : 1
  • D
    1 : 2
Answer
  1. 1 : 1

Explanation:

The ratio of moles of atoms in 12g of Magnesium and 16g of Sulphur will be 1 : 1

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MCQ 431 Mark
In which of the following, the valency of each of the constituent elements is equal to the total number of atoms in one molecule of the compound?
  • A
    HCl
  • B
    H2S
  • C
    MgCl2
  • D
    CaO
Answer
  1. CaO

Explanation:

In the compound Calcium Oxide (CaO)

There are two atoms: one of Calcium (Ca) and the other of Oxygen (O)

We know that Calcium is a metal whereas Oxygen is a non-metal

Atomic number of Calcium is “20”

Hence, its electronic configuration is 2, 8, 2

Since it has 2 valence electrons, its valency is 2

On the other hand, oxygen is a non metal with atomic number 8

Hence, its electronic configuration is: 2, 6.

So, its valency is 8 - 6 = 2(-2).

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MCQ 441 Mark
The nucleus of an atom is made up of ___________________.
  • A
    Protons and Neutrino
  • B
    Neutrons and Electrons
  • C
    Protons and Neutrons
  • D
    Protons and Electrons
Answer
  1. Protons and Neutrons
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MCQ 451 Mark
A particle P has 18 electrons, 20 neutrons and 19 protons. This particle must be:
  • A
    A molecule.
  • B
    A binary compound.
  • C
    An anion.
  • D
    A cation.
Answer
  1. A cation.

Explanation:

Particle P must be a cation.

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MCQ 461 Mark
A substance formed by the reaction of hydrogen and oxygen is called a/ an:
  • A
    Element
  • B
    Compound
  • C
    Solution
  • D
    Mixture
Answer
  1. Compound

Explanation: 

When hydrogen and oxygen are reacted, water is formed.

2H2​ + O2 ​→ 2H2​O

Water is a compound and its properties are different from the properties of both hydrogen and oxygen.

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MCQ 471 Mark
Who postulated that matter is made up of very small particles in 430 BC?
  • A
    Democritus
  • B
    Aristotle
  • C
    Dalton
  • D
    Robert Brown
Answer
  1. Democritus

Explanation:

Democritus postulated that matter is made up of very tiny particles i.e atom. In approximately 430 B.C.

Democritus coined the term atoms, which means “un-cuttable” or “the smallest indivisible particle of matter.

They are homogeneous, contain no void and no interstices, and are in perpetual motion moving equally in all directions.

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MCQ 481 Mark
Elements are made of:
  • A
    Many types of atoms
  • B
    The periodic table
  • C
    One type of atom
  • D
    Molecules
Answer
  1. One type of atom
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MCQ 491 Mark
 A change in the physical state can be brought about:
  • A
    Only when energy is given to the system.
  • B
    Only when energy is taken out from the system.
  • C
    When energy is either given to, or taken out from the system.
  • D
    Without any energy change.
Answer
  1. When energy is either given to, or taken out from the system.
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MCQ 501 Mark
Molecular compounds are usually formed by the combination between:
  • A
    A metal and a non-metal.
  • B
    Two different non-metals.
  • C
    Two different metals.
  • D
    Any two gaseous elements.
Answer
  1. Two different non-metals.

Explanation:

Molecular compounds are formed by the combination of two different non-metals.

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