MCQ

MCQ 11 Mark

Which of the following statements are correct?
Neutrons have

A
No mass
B
A mass less than that of a proton
C
A mass equal to that of a helium atom
D
Mass greater than that of a neutron

Answer

No electric charge.

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MCQ 21 Mark

Which of the following statements are correct? Electrons have

A
No mass
✓
A mass less than that of a proton
C
A mass less than not that of a proton
D
Mass greater than that of a proton

Answer

Correct option: B.

A mass less than that of a proton

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MCQ 31 Mark

Which one of the following statements about alpha and beta particles is
correct?

A
they carry equal amounts of charge
B
each alpha paticle has four times the mass of beta particle
C
They can both be deflected by magnetic fields when they are in motion
D
alpha particles have a larger range in air then beta particles

Answer

Answer is (iii) as both alpha and beta particles are deflected by magnetic

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MCQ 41 Mark

An element P has an atomic mass of 239 and an atomic number of 92. It
emits a beta particle forming an element Q. Q can be represented by.

A
$239 \times 91$
B
$239 \times 92$
✓
$239 \times 93$
D
$238 \times 92$

Answer

Correct option: C.

$239 \times 93$

Initially element is represented by $92 p ^{239}$
$\beta$ particle is represented by $-1 e^{\circ}$ after emitting a $\beta$ particle atomic number of element would increase by 1 unit and mass number of element would remain unchanged.
So after emitting a $\beta$ particle ${ }_{92} p^{239}$ would become ${ }_{92+1} p^{239}=93 p^{239}$.
${ }_b Q^a=93 P^{239}$
So answer is $C$.

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MCQ 51 Mark

The element X has an atomic mass number of 238 and an atomic number
of 92. It emits an alpha particle forming an element y. Y can be represented
by

✓
$234 \times 90$
B
$236 \times 90$
C
$235 \times 91$
D
$238 \times 92$

Answer

Correct option: A.

$234 \times 90$

Initially element is represented by $9_{22} x ^{238}$
a particle is represented by ${ }_2 He ^4$ this means it contains 2 protons and 2
neutrons so mass of a particle is 4 unit. Thus after emitting a particle mass
number of element would decrease by 4 unit and atomic number of element would decrease by 2 .
So after emitting a particle $92 x^{238}$ would become $92-2 x^{23 a-4}=90 x^{234}$.
$b Q ^{ a }=93 p ^{239}$
So answer is A .

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MCQ 61 Mark

A radioactive nuclide ${ }_{86}^{226}$ Ra decays by emission of two alpha particles, one beta particle and gamma rays. Which of the following is the resulting nuclide $X$ ?

A
$223 \times 83$
✓
$218 \times 83$
C
$218 \times 84$
D
$217 \times 85$

Answer

Correct option: B.

$218 \times 83$

Initially element is represented by ${ }_{86} Ra ^{226}$
a particle is represented by ${ }_2 He ^4$ this means it contains 2 protons and 2
neutrons so mass of a particle is 4 unit. Thus after emitting a particle mass number of element would decrease by 4 unit and atomic number of element would decrease by 2 .
So after emitting 2 a particle ${ }_{86} Ra ^{226}$ would become $86-2-2 Ra { }^{226-4-4}={ }_{82} Ra ^{218}$.
$\beta$ particle is represented by $-1 e^{\circ}$ after emitting a $\beta$ particle atomic number of element would increase by 1 unit and mass number of element would remain unchanged.
So after emitting a p particle ${ }_{82} Ra ^{218}$ would become $82+1 Ra ^{218}=83 Ra ^{218}$
Gamma radiations have zero mass and no charge so after emission of gamma radiation mass and atomic number remains unaltered.
The daughter nucleus is represented by $b x^a$
$b x^a={ }_{83} R^{218}$
So answer is B.

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MCQ 71 Mark

Make the correct choices in the following:
(a) In one atom of copper (mass number 63, atomic number 29) there are

A
63 protons and 29 neutrons
✓
63 protons and 29 electrons
C
29 protons and 29 neutrons
D
29 protons and 29 electrons

Answer

Correct option: B.

63 protons and 29 electrons

Mass number of copper = 63
Atomic number of copper = 29
As atomic number of element gives number of proton and electrons while mass number of element gives number of protons +number of neutrons.
So, number of protons in copper = atomic number of copper = 29.
Number of electron in copper = number of protons in copper =29.
Number of neutrons = mass number atomic number = 63 29 =34.
So answer is (iv) as copper contains 29 protons and 29 electrons.

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