Atoms Test

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Atoms Test - 65

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Weekly Quiz Competition

Question 1
1 / -0

In Bohr's model of hydrogen atom, which of the following pairs of quantities are quantized

A
Energy and linear momentum

B
Linear and angular momentum

C
Energy and angular momentum

D
None of these

Solution
Question 2
1 / -0

The boher model of atoms

A
Assume that the angular momentum of electrons is quantized

B
Uses Einstein's photo electric equation

C
Predicts continuous emission spectra for atoms

D
Predicts the same emission spectra for all types of atoms

Solution

Bohr defined stable orbits of electron revolution in his second postulate. According to this postulate:

· An electron revolves around the nucleus in orbits.

· The angular momentum of revolution is an integral multiple of h/2π where h is Planck’s constant.
Hence, the angular momentum (L) of the orbiting electron is: L = nh/2π, which is quantized. (Option A is correct)
Question 3
1 / -0

The possible quantum number for $$3d$$ electron are

A
$$n=3, l=1, m_1=+1, m_s=-\dfrac 12$$

B
$$n=3, l=2, m_1=+2, m_s=-\dfrac 12$$

C
$$n=3, l=1, m_1=-1, m_s=+\dfrac 12$$

D
$$n=3, l=0, m_1=+1, m_s=-\dfrac 12$$

Solution
Question 4
1 / -0

The radius of the first ( lowest ) orbit of the hydrogen atom is $$a_0$$. The radius of the second ( next higher ) orbit will be

A
$$4a_0$$

B
$$6a_0$$

C
$$8a_0$$

D
$$10a_0$$

Solution

$$r_n=\dfrac{n^2}{z}a_b$$
$$r_1=\dfrac{1}{L}a_0$$
$$r_1=a_0$$
$$r_2=\dfrac{(2)^2}{1}a_0$$
$$r_2=4a_0$$
Question 5
1 / -0

Radius of first Bohr orbit is $$r$$. What is the radius of $$2-$$Bohr orbit?

A
$$8\ r$$

B
$$2\ r$$

C
$$4\ r$$

D
$$2\ \sqrt {2r}$$

Solution
Question 6
1 / -0

Which of the following is quantised according to Bohr's theory of hydrogen atom

A
Linear momentum of electron

B
Angular momentum of electron

C
Linear velocity of electron

D
Angular velocity of electron

Solution
Question 7
1 / -0

The spectrum obtained from a sodium vapour lamp is an example of

A
Absorption spectrum

B
Emission spectrum

C
Continuous spectrum

D
Band spectrum

Solution

Sodium light gives emission spectrum having two yellow lines.
Question 8
1 / -0

The colour of the second line of Balmer series is

A
Blue

B
Yellow

C
Red

D
Violet

Solution
Question 9
1 / -0

When light emitted by a white hot solid is passed through a sodium flame, the spectrum of the emergent light will show

A
The $$D_{1}$$ and $$D_{2}$$ bright yellow lines of sodium

B
Two dark lines in the yellow region

C
All colours from violet to red

D
No colours at all

Solution

When light emitted by a white hot solid passes through sodium vapour then cooler sodium vapour absorb energy from white light spectrum producing spectrum of bright yellow light with two dark lines in the yellow region.
Question 10
1 / -0

When a hydrogen atom is raised from ground to excited state.

A
The P.E increases and K.E decreases

B
The P.E decreases and K.E increases

C
Both P.E and K.E increase

D
Both P.E and K.E decreases

Solution

Potential energy of hydrogen atom is given by
$$P.E=\dfrac{-kZe}{r}$$
As atom is excited,it's radius increases. But due to negative sign or reverse sign. Its actual potential energy increases.
And kinetic energy is given by
$$K.E=\dfrac{kZe}{2r}$$
As Tom is excited, it's radius increases this resulting in decrease of kinetic energy.
The PE increases and KE decreases.