**Answer the following questions:-**

**(i)** Calculate the total number of electrons present in one mole of methane.

**(ii)** Find

(a) the total number and

(b) the total mass of neutrons in 7 mg of ^{14}C.

(Assume that mass of a neutron = 1.675 × 10^{–27} kg).

**(iii)** Find

(a) the total number and

(b) the total mass of protons in 34 mg of NH_{3 }at STP.

Will the answer change if the temperature and pressure are changed?

Asked by Pragya Singh | 1 year ago | 82

**(i) **1 molecule of methane contains 10 electrons (6 from carbon, 4 from hydrogen)

Therefore, 1 mole of methane contains \( 10\times N_A \)

= \( 6.022\times 10^{24}\) electrons.

**(ii) **

(a)** **Number of neutrons in 14g (1 mol) of ^{14}C

=\( 8\times N_A\)

=\( 4.817\times 10^{24}\) neutrons.

Number of neutrons in 7 mg (0.007g)

= (\( \dfrac{0.007}{14}\times 4.817\times 10^{24}\))

= \( 2.409\times 10^{21}\) neutrons.

(b) Mass of neutrons in 7 mg of ^{14}C

= \( (1.67493\times 10^{-27}kg)\times(2.409\times 10^{21}) \)

= \( 4.03\times 10^ {-6}kg\)

**(iii) **

(a) Molar mass of NH_{3} = 17g

Number of protons in 1 molecule of NH_{3} = 7+3 = 10

Therefore, 1 mole (17 grams) of NH_{3} contains \( 10\times N_A \)

=\( 6.022\times 10^{24}\) protons.

34 mg of NH_{3} contains

(\(\dfrac{34}{1700})\times 6.022\times 10^{24}\) protons

= \( 1.204\times 10^{22}\) protons.

(b) Total mass accounted for by protons in 34 mg of NH_{3}

= \( (1.67493\times 10^{-27}kg)\times (1.204\times10^{22})\)

= \( 2.017\times 10^{-5}kg\).

These values remain constant regardless of any change in temperature and pressure (since these factors do not affect the number of protons in the atom and the mass of each proton).

Answered by Pragya Singh | 1 year agoAnswer the following questions:-

**(a)** How many sub-shells are associated with n = 4?

**(b)** How many electrons will be present in the sub-shells having m_{s} value of \(- \dfrac{1}{2}\) for n = 4?

Indicate the number of unpaired electrons in:

**(a)** P

**(b) **Si

**(c)** Cr

**(d)** Fe

**(e)** Kr

The unpaired electrons in Al and Si are present in 3p orbital. Which electrons will experience more effective nuclear charge from the nucleus?

Among the following pairs of orbitals which orbital will experience the larger effective nuclear charge?

**(i) **2s and 3s,

**(ii)** 4d and 4f,

**(iii)** 3d and 3p

The bromine atom possesses 35 electrons. It contains 6 electrons in 2p orbital, 6 electrons in 3p orbital and 5 electrons in 4p orbital. Which of these electron experiences the lowest effective nuclear charge?