(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

a. `1` molecule of methane contains electrons `=6+4=10`
`6.022xx10^(23)` molecules `(1 "mole")` of methnane contain electron `=6.022xx10^(23)xx10=6.022xx10^(24)`
b. a. `14 g` of carbon has `6.022xx10^(23)` neutrons
`7xx10^(-3) g` of carbon has
`=(6.022xx10^(23)xx7xx10^(-3))/(14)=3.011xx10^(20)`
b. Mass of `1` neturon `=1.675xx10^(-27) kg`
Mass of `3.011xx10^(20)` neutrons
`=1.675xx10^(-27)xx3.011xx10^(20)kg`
`=5.04xx10^(-7) kg`
c. i. `17 g` of `NH_(3)` has `6.022xx10^(23)` protons
`34xx10^(-3)g` of `NH_(3)` have
`(6.022xx10^(23)xx34xx10^(-3))/(17)` protons
`=12.044xx10^(20)`
`=1.2044xx10^(21)`
ii. Mass of `1` proton `=1.67xx10^(-27) kg`
Mass of `1.2044xx10^(20)` protons
`=1.2044xx10^(20)xx1.67xx10^(-27)`
`=2.01xx10^(-7) kg`