In the hydrogen atom spectrum, the emission of the least energetic photon takes place during the transition from n = 6 energy level to n = .......... energy level.

• 1

• 3

• 5

• 4

The threshold frequency of a metal corresponds to the wavelength of x nm. In two separate experiments A and B, incident radiations of wavelengths 1/2x nm and 1/4x nm respectively are used. The ratio of kinetic energy of the released electrons in experiment 'B' to that in experiment 'A' is

• 1/3

• 2

• 4

• 3

The minimum values of uncertainties involved in the determination of both the position and velocity of a particle respectively are 1 × 10^-10 m and 1 × 10^-10 ms^-1.Then, the mass (in kg) of the particle is

• 5.270 × 10^-15

• 5.270 × 10^-20

• 5.270 × 10^-16

• 5.270 × 10^-10

The number of electrons with azimuthal quantum number l = 1 and l = 2 for Cr in ground state respectively are

• 12, 5

• 12, 4

• 16, 5

• 16, 4

In which one of the following, d-d transition involves absorption in the ultraviolet region?

• [Cu(H₂O)₄]²⁺

• [Ti(H₂O)₆]³⁺

• [Co(NH₃)₆]³⁺

• [Co(CN)₆]^3-

The shortest wavelength of the line in hydrogen atomic spectrum of Lyman series when R_H = 109678 cm^-1 is

• 1002.7 Å

• 1215.67 Å

• 1127.30 Å

• 911.7 Å

Which of the following are isoelectronic species?

(i) NH₃

(ii) CH${}_3^{+}$

(iii) NH${}_2^{-}$

(iv) NH${}_4^{+}$

Choose the correct answer from the codes given below.

• (i), (ii), (iii)

• (ii), (iii), (iv)

• (i), (ii), (iv)

• (i), (iii), (iv)

78.

The ratio of the frequency corresponding to the third line in Lyman series of hydrogen atomic spectrum to that of the first line in Balmer series of Li²⁺ spectrum is

• $\frac{4}{5}$

• $\frac{5}{4}$

• $\frac{4}{3}$

• $\frac{3}{4}$

The number of electrons, neutrons and protons in a species are equal to 10, 8 and 8 respectively. The proper symbol of the species

• ${}_8{}^{16}\mathrm{O}$

• ${}_8{}^{16}\mathrm{O}^{2-}$

• ${}_8{}^{16}\mathrm{O}^{-}$

• ${}_8{}^{18}\mathrm{O}$

A 600 W mercury lamp emits monochromatic radiation of wavelength 331.3 nm. How many photons are emitted from the lamp per second? (h = 6.626 x 10^-34 Js; velocity of light = 3×10⁸ ms^-1).

• 1 × 10¹⁹

• 1 × 10²²

• 1 × 10²¹

• 1 × 10²³