(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 = $1.675 \times 10^{- 27} k g$ ).

(iii) Find (a) the total number and (b) the total mass of protons in 34 mg of $N H_{3}$ at STP.
Will the answer change if the temperature and pressure are changed?

Question

(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 \times 10^{- 27} k g

).

(iii) Find (a) the total number and (b) the total mass of protons in 34 mg of

N H_{3}

at STP.
Will the answer change if the temperature and pressure are changed?

Filo · Accepted Answer

(i) Total number of electrons present in 1 methane molecule

= 6 + 4 = 10

.

Total number of electrons resent in 1 mole of methane

= 10 \times 6.023 \times 1 0^{23} = 6.023 \times 1 0^{24}

electrons.

The number of neutrons is equal to the difference in the mass number and atomic number.
It is equal to

14 - 6 = 8

.

(ii)(a) The number of neutrons present in 7 mg of C-14 is

\frac{6.023 \times 1 0 ^{23} \times 8}{14} \times 7 \times 1 0^{10 - 3} = 2.4088 \times 1 0^{21}

neutrons.

(b) Total mass of neutrons in 7 mg of C-14 is

2.4088 \times 1 0^{21} \times 1.675 \times 1 0^{- 27} 4.035 \times 1 0^{- 6}

kg.

(iii)(a)Number of protons present in 1 molecule of ammonia

= 7 + 3 = 10

.

Number of molecules present in 34 mg of ammonia is

\frac{6.023 \times 1 0 ^{23} \times 34 \times 1 0 ^{- 3}}{17} = 1.2044 \times 1 0^{21}

.

Total number of protons present in 34 mg of ammonia

= 10 \times 1.2044 \times 1 0^{21} = 1.2044 \times 1 0^{22}

(b) Total mass of protons present in 34 mg of ammonia at STP is

1.6726 \times 1 0^{- 27} \times 1.204 \times 1 0^{22} = 2.0138 \times 1 0^{- 5}

kg.

When temperature and pressure are changed, there is no difference in the answer.

Question Text	(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 = $1.675 \times 10^{- 27} k g$ ). (iii) Find (a) the total number and (b) the total mass of protons in 34 mg of $N H_{3}$ at STP. Will the answer change if the temperature and pressure are changed?
Answer Type	Text solution:1
Upvotes	150

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