Atoms Test

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Atoms Test - 64

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following is true for number of spectral lines in going form Layman series to Pfund series

A
Increases

B
Decreases

C
Unchanged

D
May decreases or increases

Solution
Question 2
1 / -0

In bohr's model, if the atomic radius of the first orbit is $$r_0$$, then the radius of the fourth orbit is

A
$$r_0$$

B
$$4r_0$$

C
$$r_0/16$$

D
$$16r_0$$

Solution

$$r_n \propto n^2\Rightarrow \dfrac {r_4}{r_1}=\left( \dfrac 41 \right)^2 =\dfrac {16}{1}\Rightarrow r_4=16r_1 \Rightarrow r_4=16\ r_0$$
Question 3
1 / -0

For principal quantum number $$n=3$$, the possible values of orbital quantum number $$'I$$ are

A
$$1, 2, 3$$

B
$$0, 1, 2, 3$$

C
$$0, 1, 2$$

D
$$-1, 0, +1$$

Solution

For $$M$$ shell $$(n=3)$$, orbital quantum number $$I=0, 1, 2$$.
Question 4
1 / -0

Radius of the first orbit of the electron in a hydrogen atom is $$0.53\ A^o$$. So, the radius of the third orbit will be

A
$$2.12\ A^o$$

B
$$4.77\ A^o$$

C
$$1.06\ A^o$$

D
$$1.59\ A^o$$

Solution

$$r_n \propto n^2 \Rightarrow \dfrac{r_3}{r_1}=\dfrac{3^2}{1}$$
$$\Rightarrow r_3=9r_1=9\times 0.53 =4.77\ A^o$$
Question 5
1 / -0

In Bohr model of hydrogen atom, the ratio of periods of revolution of an electron in $$n=2$$ and $$n=1$$ orbits is

A
$$2:1$$

B
$$4:1$$

C
$$8:1$$

D
$$16:1$$

Solution

$$T \propto n^3 \Rightarrow \dfrac {T_2}{T_1}$$
$$=\dfrac{2^3}{1^3}=\dfrac 81$$
Question 6
1 / -0

The ratio of the speed of the electron in the first Bohr orbit of hydrogen and the speed of light is equal to ( where $$e, h$$ and $$c$$ have their usual meanings)

A
$$2\pi hc/e^2$$

B
$$e^2h/2\pi c$$

C
$$e^2c/2\pi h$$

D
$$2\pi e^2 /hc$$

Solution

Speed of electron in $$\pi$$ orbit ( in CGS) $$v_n=\dfrac{2\pi Ze^2}{nh}\ (k=1)$$
For first orbit $$H_2$$; $$n=1$$ and $$Z=1$$
So $$v=\dfrac{2\pi e^2}{h}\Rightarrow \dfrac vc =\dfrac {2\pi e^2}{hc}$$
Question 7
1 / -0

In hydrogen atom which quantity is integral multiple of $$\dfrac{h}{2\pi}$$

A
Angular momentum

B
Angular velocity

C
Angular acceleration

D
Momentum

Solution
Question 8
1 / -0

Energy of an electron in an excited hydrogen atom is $$-3.4\ eV$$. Its angular momentum will be : $$h=6.626\times 10^{-34}\ J-s$$

A
$$1.11 \times 10^{34}\ J\ sec$$

B
$$1.51 \times 10^{31}\ J\ sec$$

C
$$2.11 \times 10^{34}\ J\ sec$$

D
$$3.72 \times 10^{34}\ J\ sec$$

Solution

The electron is in the second orbit $$(n=2)$$
Hence $$L=\dfrac{nh}{2\pi}=\dfrac{2h}{2\pi}$$
$$=\dfrac{6.6\times 10^{-34}}{\pi}=2.11\times 10^{-34}\ J-sec$$
Question 9
1 / -0

Which of the following spectral series in hydrogen atom give spectral line of $$4860\ A^o$$

A
Lyman

B
Balmer

C
Paschen

D
Brackett

Solution
Question 10
1 / -0

In hydrogen atom, when electron jumps from second to first orbit, then energy emitted is

A
$$-13.6\ eV$$

B
$$-27.2\ eV$$

C
$$-6.8\ eV$$

D
$$None\ of\ these$$

Solution

$$E_{n_1 \to n_2}=-13.6 \left[ \dfrac{1}{n_2^2}-\dfrac{1}{n_1^2}\right]; n_1=2$$ & $$n_2=1$$
$$\Rightarrow E_{II}\to E_I=-13.6 \times \dfrac 34=-10.2\ eV$$

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Atoms Test - 64

Result

Atoms Test - 64

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Question 1

Increases

Decreases

Unchanged

May decreases or increases

Solution

Question 2

$$r_0$$

$$4r_0$$

$$r_0/16$$

$$16r_0$$

Solution

Question 3

$$1, 2, 3$$

$$0, 1, 2, 3$$

$$0, 1, 2$$

$$-1, 0, +1$$

Solution

Question 4

$$2.12\ A^o$$

$$4.77\ A^o$$

$$1.06\ A^o$$

$$1.59\ A^o$$

Solution

Question 5

$$2:1$$

$$4:1$$

$$8:1$$

$$16:1$$

Solution

Question 6

$$2\pi hc/e^2$$

$$e^2h/2\pi c$$

$$e^2c/2\pi h$$

$$2\pi e^2 /hc$$

Solution

Question 7

Angular momentum

Angular velocity

Angular acceleration

Momentum

Solution

Question 8

$$1.11 \times 10^{34}\ J\ sec$$

$$1.51 \times 10^{31}\ J\ sec$$

$$2.11 \times 10^{34}\ J\ sec$$

$$3.72 \times 10^{34}\ J\ sec$$

Solution

Question 9

Lyman

Balmer

Paschen

Brackett

Solution

Question 10

$$-13.6\ eV$$

$$-27.2\ eV$$

$$-6.8\ eV$$

$$None\ of\ these$$

Solution

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