21.

C₆H₅F¹⁸ is a F¹⁸  radio-isotope labelled organic compound. F¹⁸ decays by positron emission. The product resulting on decay is 

• C₆H₅O¹⁸

• C₆H₅Ar¹⁹

• B¹²C₅H₅F

• C₆H₅O¹⁶

The energy required to break one mole of hydrogen-hydrogen bonds in H₂ is 436 kJ. What is the longest wavelength of light required to break a single hydrogen-hydrogen bond?

• 68.5nm

• 137nm

• 274nm

• 584nm

An element E loses one $\mathrm{\alpha }$ and two $\mathrm{\beta }$ particles in three successive stages. The resulting elemenl wiil be

• an isobar of E

• an isotone of E

• an isotope of E

• E itself

Which one of the following corresponds to a photon of highest energy?

• λ = 300 mm

• v = 3 × 10⁸ s^-1

• $\overline{\mathrm{v}}$ = 30 cm^-1

• ε = 6.626 × 10^-27 J

The time taken for an electron to complete one revolution in Bohr orbit of hydrogen atom is

• $\frac{4{\mathrm{m}}^2{\mathrm{\pi r}}^2}{{\mathrm{n}}^2{\mathrm{h}}^2}$

• $\frac{{\mathrm{n}}^2{\mathrm{h}}^2}{4{\mathrm{mr}}^2}$

• $\frac{4{\mathrm{\pi }}^2{\mathrm{mr}}^2}{\mathrm{nh}}$

• $\frac{\mathrm{nh}}{4{\mathrm{\pi }}^2{\mathrm{mr}}^2}$

Amongst the following, which should have the highest rms speed at the same temperature?

• SO₂

• CO₂

• O₂

• H₂

The emission spectrum of hydrogen discovered first and the region of the electromagnetic spectrum in which it belongs, respectively are

• Lyman, ultraviolet

• Lyman, visible

• Balmer, ultraviolet

• Balmer, visible

The electronic configuration of Cu is

• [Ne] 3s²,3p⁶,3d⁹,4s²

• [Ne] 3s²,3p⁶, 3d¹⁰, 4s¹

• [Ne] 3s²,3p⁶, 3d³,4s², 4p⁶

• [Ne] 3s²,3p⁶,3d⁵,4s²,4p⁴

As per de-Broglie's formula a macroscopic particle of mass 100 g and moving at a velocity of 100 cm s^-1 will have a wavelength of

• 6.6 x 10^-29 cm

• 6.6 x 10^-30 cm

• 6.6 x 10^-31 cm

• 6.6 x 10^-32 cm

During the emission of a positron from a nucleus, the mass number of the daughter element remains the same but the atomic numbe

• is decreased by 1 unit

• is decreased by 2 units

• is increased by 1 unit

• remains unchanged