The shortest wavelength of the line in hydrogen atomic spectrum o

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81.

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

  • 1002.7 Å

  • 1215.67 Å

  • 1127.30 Å

  • 911.7 Å


D.

911.7 Å

According to Rydberg's formula-

1λ = RHZ21n12 - 1n22

For hydrogen, Z = 1 and 

For lyman series, n1 = 1 and n2 = ∞ (for shortest wavelength)

On substituting values, we get

1λ = 109678 × 12 × 112 - 12     = 109678 cm-1

λ   = 1109678 cm-1

     = 9.117 × 10-6 cm

     = 911.7 × 10-8 cm

     = 911.7 Å


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82.

Which of the following are isoelectronic species?

(i) NH3

(ii) CH3+

(iii) NH2-

(iv) NH4+

Choose the correct answer from the codes given below.

  • (i), (ii), (iii)

  • (ii), (iii), (iv)

  • (i), (ii), (iv)

  • (i), (iii), (iv)


83.

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

  • 45

  • 54

  • 43

  • 34


84.

Which transition in the hydrogen atomic spectrum will have the same wavelength as the transition will have the same wavelength, n = 4 to n = 2 of He+ spectrum?

  • n = 4 to = 3

  • n = 2 to n = 1

  • n = 4 to n = 2

  • n = 3 to n = 1


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85.

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

  • O816

  • O2-816

  • O-816

  • O818


86.

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


87.

The shortest wavelength in hydrogen spectrum of Lyman series when RH = 109678 cm-1 is

  • 1002.7 Å

  • 1215.67 Å

  • 1127.30 Å

  • 911.7 Å


88.

The electrons, identified by quantum numbers n and l,

(I) = 3; l = 2; (II) = 5; l = 0; (III) = 4; l = 1; (IV) = 4; l = 2; (V) = 4; l = 0;

can be placed in order of increasing energy as-

  • I < V < III < IV < II

  • I < V < III < II < IV

  • V < I < III < II < IV

  • V < I < II < III < IV


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89.

The number of photons emitted per second by a 60 W source of monochromatic light of wavelength 663 nm is (h = 6 .63 × 10-34 Js)

  • 4 × 10-20

  • 1.5 × 1020

  • 3 × 10-20

  • 2 × 1020


90.

Energy released, when one atom of uranium undergoes nuclear fission according to the following reaction is (atomic mass of U = 235.060; n = 1.009; Ba= 143.881 and Kr = 89.94 7) about 

92U2350n1 → 56Ba14436Kr90 + 2 0n1

  • 235 MeV

  • 208 MeV

  • 931.5 MeV

  • 5.33 x 1023 MeV


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