Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. The work function (W₀) of the metal is: 

1. 3.109 × 10^–20 J

2. 2.922 × 10^–19 J

3. 4.031 × 10¹⁹ J

4. 2.319 × 10^–18 J

Determine the maximum number of emission lines produced when an electron in a hydrogen atom transitions from the n = 6  energy level to the ground state :

1. 30

2. 21

3. 15

4. 28

The ionization energy for H atom in the ground state is \(2.18 \times10^{-18}~ \mathrm J.\) The process energy requirements will be: \(( He^+(g) \rightarrow He^{2+}(g) + e^- )\)

Calculate the work function of silver metal, given that a stopping voltage of 0.35 eV is applied and the radiation has a wavelength of 256.7 nm.

1. 3.40 eV

2. 5.18 eV

3. 4.48 eV

4. –4.40 eV

Property which is same for the following species is:

 N^3–, O^2–, F^–, Na⁺, Mg²⁺ and Al³⁺ 

1. Ionic radii

2. Number of electrons

3. Nuclear charge

4. None of the above 

$1.$ $6.023$ $\times$ ${10}^{23}$
$2.$ $6.023$ $\times$ ${10}^{24}$
$3.$ $6.023$ $\times$ ${10}^{22}$
$4.$ $1.619\times$ ${10}^{23}$

The total number and mass of neutrons in 7 mg of ¹⁴C would be :

(Assume that mass of a neutron = 1.675 × 10^–27 kg)

\(1 .\) \(2 . 41\) \(\times\) \(\left(10\right)^{21}\) \(,\) \(4 . 03\) \(\times\) \(\left(10\right)^{– 6}\) \(kg\)
\(2 .\) \(6 . 23\) \(\times\) \(\left(10\right)^{23}\) \(,\) \(1 . 67\) \(\times\) \(\left(10\right)^{- 21} kg\)
\(3 .\) \(1 . 22\) \(\times\) \(\left(10\right)^{22}\) \(,\) \(4 . 03\) \(\times\) \(\left(10\right)^{6}\) \(kg\)
\(4 .  2 . 41\) \(\times\) \(\left(10\right)^{21}\) \(,\) \(4 . 03\) \(\times\) \(\left(10\right)^{- 6}\) \(g\)

The wave number of a light whose time period is 2.0 × 10^–10 s would be:

1. 16.66 m^–1

2. 1.66 m^–1

3. 32.34 m^–1

4. 12.34 m^–1

The number of photons of light with a wavelength of 4000 pm that provide 1J of energy would be: 

$1.$ $2.01$ $\times$ ${10}^{16}$
$2.$ $2.01$ $\times$ ${10}^{19}$
$3.$ $4.14$ $\times$ ${10}^{23}$
$4.$ $2.14$ $\times$ ${10}^{21}$

Electromagnetic radiation of wavelength 242 nm is just sufficient to ionise sodium atom. The ionisation energy of sodium in kJ mol^–1 is :

1. 494

2. 4.94

3. 516

4. 0.50