(i) As we know in 1 molecule of methane, 1 carbon atom and 4 atoms of hydrogen is present.

In carbon there are six electrons and hydrogen consist of one electron each.

So total number of electrons in methane = 6 + 4

= 10 electrons

By Avogadro’s Law we know that

1 mole of methane contains 6.023×10²³ atoms.

So total number of electrons of in 1 mole methane = 10×6.023×10²³

= 6.023×10²⁴ electrons

So total number of electrons in 1 mole of methane is 6.023×10²⁴ electrons

(ii) Mass of one neutron = 1.675 × 10^–27 kg

1 mole of Carbon atom = 6.023×10²³ atoms

Number of neutrons in 1 carbon atom = 14-6= 8

So total number of neutrons in 14g of Carbon = 6.023×10²³×8 neutrons

So 7mg of Carbon will contain =

= [3.37288×10²²]/14

= 2.4092×10²¹ neutrons

So, Mass of 2.4092×10²¹ neutrons = [2.4092×10²¹] × [1.675 × 10^–24]

= 4.035×10^–3 g

So, in 7 mg of carbon total number of neutrons is 2.41×10²¹ and the total mass of the neutrons is 4.035× 10^–3 g

(iii) Molecular Mass of Ammonia = 17g

By Avogadro’s Law,

1 mole of Ammonia = 17g of Ammonia = 6.023×10²³ atoms

Total Number of Protons in Ammonia = 7 + 3= 10

So total number of protons in Ammonia = 6.023×10²⁴ protons

17g of Ammonia contain 6.023×10²⁴ protons

So, 34 mg of Ammonia will contain X number of protons

X =

X = [6.023×10²⁴] × [2×10^-3]

X = 1.2046×10²² protons

Mass of one proton = 1.6726 × 10^–24g

So, Mass of 1.2046×10²² protons = [1.6726 × 10^–24] × [1.2046×10²²]

= 20.148×10^-3 g

So, in 34 mg of ammonia total number of protons is 1.205×10²² and the total mass of the protons is 20.148×10^-3 g.

(iv) No, the answer will not vary with the change in temperature and pressure because the number of subatomic particles like protons, neutrons and electrons is fixed for each and every element and it does not vary with temperature and pressure.