(i) Calculate the total number of electrons present in 1 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 . 6 75 xx 10 ^(-27) g)`
(iii) Find (a) the total mnumber of protons and (b) the total mass fo protons in ` 32 mg` of ` NH_3` at ` STP`. ( mass of proton ` = 1 . 6 72 xx 10^(-27) g)`
Will the answer change if the temperature and pressure are changed ?

Explanation

(i) `1` mole `CH_4 = N` molecule `CH_4`
`Nxx 10` electron
` = 6. 023 xx 10 ^(24)` electron
(ii) (a) An atom of `._6 C^(14)` has 8 neutrons
` 7 mg ._6 C^(14) = 7 xx 10^(-3) g = ( 7 xx 10^(-3))/(14) mol e `
`= ( 7 xx 10^(-3) xx 6. 023 xx 10^(23))/(14) at om `
`therefore` No. of neutron ` = ( 7 xx 10^(-3) xx 6.023 xx 10^(23) xx 8)/(14)`
`= 24 . 09 xx 10^(20)`
( b) Mass of of neutrons
`= 24 . 09 xx 10^(20) xx 1.675 xx 10^(-27)`
`= 40.35 xx 10^(-7) kg`
(iii) ` 35 mg NH_3 = 34 xx 10^(-3) g NH_3`
` = 34 xx 10^(-30)/(17) mol e NH_3`
` =2 xx 10^(-3) mol e NH_3`
` = 2 xx 10^(-3) xx 6.025 xx 10^(23) ` molecule `NH_3`
` = 12. 046 xx 10^(20)" molecule "NH_3`
(a) therefore Number of proton in 1 molecule ` nH-3 = 10`
therefore Total no. of proton ` = 12.046 xx 10^(20) xx 10`
` = 1.2046 xx 10^(22)`
(b) Mass of total proton
` = 1. 2046 xx 10^(22) xx 1. 672 xx 10^(-27)`
` = 2. 0 14 xx 10^(-5) kg`
N0, the answer will not chage since mass fo ` NH_3` does not depend on (P) and (T) .