# <!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> The total number of electrons present in one mole of methane is: $1.$ $6.023$ $×$ ${10}^{23}$$2.$ $6.023$ $×$ ${10}^{24}$$3.$ $6.023$ $×$ ${10}^{22}$$4.$ $1.619×$ ${10}^{23}$

Subtopic:  Number of Electron, Proton & Neutron |
60%
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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)

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

Subtopic:  Number of Electron, Proton & Neutron |
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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

Subtopic:  Introduction of Atomic Structure |
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The number of photons of light with a wavelength of 4000 pm that provide 1J of energy would be:

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

Subtopic:  Planck's Theory |
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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

Subtopic:  Planck's Theory |
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A 25-watt bulb emits monochromatic yellow light with a wave length of 0.57µm. The rate of emission of quanta per second would be :

1. 7.17×10-19 s-1

2. 4.13×1016s-1

3 . 7.17×1019 s-1

4 . 1.26 ×1020s-1
${}^{}$

Subtopic:  Planck's Theory |
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The wavelength of light emitted when the electron in a H atom undergoes the transition from an energy level with n = 4 to an energy level with n = 2, is :

1. 586 mm

2. 486 nm

3. 523 nm

4. 416 pm

Subtopic:  Hydrogen Spectra |
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The energy associated with the fifth orbit of a hydrogen atom is :

$1.$ $-2.18$ $×$ ${10}^{-18}$ $\mathrm{J}$
$2.$ $-8.72$ $×$ ${10}^{-20}$ $\mathrm{J}$
$3.$ $-3.88$ $×$ ${10}^{-21}$ $\mathrm{J}$
$4.$ $-8.72$ $×$ ${10}^{-19}$ $\mathrm{J}$

Subtopic:  Hydrogen Spectra |
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The wave number for the longest wavelength transition in the Balmer series of atomic hydrogen would be :

1. $$1 . 1 . 52 \times \left(10\right)^{6} m^{- 1}$$
2. $$2 . 3 . 14 \times \left(10\right)^{6} \left(cm\right)^{- 1}$$
3. $$3 . 15 . 2 \times \left(10\right)^{6} m^{- 1}$$
4. $$4 . 1 . 52 \times \left(10\right)^{6} \left(cm\right)^{- 1}$$

Subtopic:  Hydrogen Spectra |
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The energy of an electron in an H - atom is given by $$E_n=(-2.18 \times10^{-18})/n^2~\mathrm J.$$ The shortest wavelength of light that can be used to remove an electron completely from $$n = 2$$ orbit will be:

 1 $$3647~\mathring{\mathrm A}$$ 2 $$5132~\mathring{\mathrm A}$$ 3 $$3017~\mathring{\mathrm A}$$ 4 None of these



Subtopic:  Hydrogen Spectra |
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