# Assertion (A): It is impossible to determine the exact position and exact momentum of an electron simultaneously. Reason (R): The path of an electron in an atom is clearly defined.  1. Both (A) and (R) are True and (R) is the correct explanation of (A). 2. Both (A) and (R) are True but (R) is not the correct explanation of (A). 3. (A) is True but (R) is False. 4. (A) is False but (R) is True.

Subtopic:  Heisenberg Uncertainty Principle |
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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 |
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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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