Atomic Structure Questions | Chemistry JEE Main Important Questions

Q 1 :

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency $' A' \times 10^{12}$ hertz and that has a radiant intensity in that direction of $\frac{1}{' B'}$ watt per steradian.

'A' and 'B' are respectively. [2024]

450 and 683
540 and $\frac{1}{683}$
540 and 683
450 and $\frac{1}{683}$

1

2

3

4

(3)

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency $540 \times 10^{12}$ Hz and that has a radiant intensity in that direction of $\frac{1}{683}$ watt per steradian.

Q 2 :

The ionization energy of sodium in kJ $m o l^{- 1}$ , if electromagnetic radiation of wavelength 242 nm is just sufficient to ionize sodium atom is ________ . [2024]

0%

(494) Energy of photon $E_{p}$ is :

$E_{p} = \frac{h c}{λ} = \frac{6.626 \times 10^{- 34} Js \times 3 \times 10^{8} {ms}^{- 1}}{242 \times 10^{- 9} m}$

lonization energy of one atom of sodium

$= Energy of one photon = \frac{6.626 \times 10^{- 34} \times 3 \times 10^{8}}{242 \times 10^{- 9}} J$

Ionization energy of one mol of sodium atoms

$= \frac{6.626 \times 10^{- 34} \times 3 \times 10^{8}}{242 \times 10^{- 9}} \times 6.022 \times 10^{23} \times \frac{1}{1000} kJ$

$= 494.65 {kJmol}^{- 1}$

Q 3 :

Wave number for a radiation having 5800 $Å$ wavelength is $x \times 10 c m^{- 1}$ . The value of $x$ is ____________ . (Integer answer) [2024]

0%

(1724) $Wave number (\bar{ν}) is reciprocal of wavelength (λ) .$

$\bar{ν} = \frac{1}{λ} = \frac{1}{5800 Å} = \frac{1}{5800 \times 10^{- 8} cm} = 1724.138 \times 10 {cm}^{- 1}$

Q 4 :

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R:

Assertion A: In the photoelectric effect, the electrons are ejected from the metal surface as soon as the beam of light of frequency greater than threshold frequency strikes the surface.

Reason R: When the photon of any energy strikes an electron in the atom, transfer of energy from the photon to the electron takes place.

In the light of the above statements, choose the most appropriate answer from the options given below: [2023]

Both A and R are correct and R is the correct explanation of A
A is correct but R is not correct
A is not correct but R is correct
Both A and R are correct but R is NOT the correct explanation of A

1

2

3

4

(2)

Electron are ejected if light has more frequency than threshold frequency. Photon is energy itself. It is absorbed.

Q 5 :

Values of work function $(W_{0})$ for a few metals are given below:

Metal Li Na K Mg Cu Ag

$W_{0} / eV$ 2.42 2.3 2.25 3.7 4.8 4.3

The number of metals which will show photoelectric effect when light of wavelength 400 nm falls on it is ________ .

Given: $h = 6.6 \times 10^{- 34} J s$

$c = 3 \times 10^{8} {m s}^{- 1}$

$e = 1.6 \times 10^{- 19} C$ [2023]

0%

(3)

The energy of photon $(E) = \frac{h c}{λ}$

Given, $λ = 400$ $nm$

$E = \frac{6.6 \times 10^{- 34} \times 3 \times 10^{8}}{400 \times 10^{- 9}}$

$E (in eV) = \frac{6.6 \times 10^{- 34} \times 3 \times 10^{8}}{400 \times 10^{- 9} \times 1.6 \times 10^{- 19}} eV = 3.1 eV$

The metals Li, Na, K have a work function less than the energy of a photon. So in presence of light with wavelength 400 nm, they exhibit photoelectric effect.

Topic Question Set

Q 1 :

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency $' A' \times 10^{12}$ hertz and that has a radiant intensity in that direction of $\frac{1}{' B'}$ watt per steradian.

'A' and 'B' are respectively. [2024]

Q 2 :

The ionization energy of sodium in kJ $m o l^{- 1}$ , if electromagnetic radiation of wavelength 242 nm is just sufficient to ionize sodium atom is ________ . [2024]

0%

Q 3 :

Wave number for a radiation having 5800 $Å$ wavelength is $x \times 10 c m^{- 1}$ . The value of $x$ is ____________ . (Integer answer) [2024]

0%

0%

Want Us to Email you About Special Offers & Updates?