Calculate the mass of (i) 0.1 mole of `KNO_(3)` (ii) `1xx10^(23)` molecules of methane and (iii) `112cm^(3)` of hydrogen at STP.

Explanation

(i) `"1 mole of "KNO_(3)=101g" "(because" Formula mass of "KNO_(3)=1xx39+1xx14+3xx16=101u)`
`therefore" 0.1 mole of KNO"_(3)=101xx0.1`
`=10.1" g og "KNO_(3)`
(ii) 1 mole of `CH_(4)=16g=6.022xx10^(23)` molecules
i.e., `6.022xx10^(23)` molecules of methane have mass = 16 g
`therefore" "1xx10^(23)` molecules of methane will have meas`=(16)/(6.022xx10^(23))xx10^(23)=2.657g.`
(iii) 1 mole of `H_(2)=2g=22400cm^(3)` at STP, i.e., 22400 `cm^(3)` of `H_(2)` at STP have mass = 2 g
`therefore" "112cm^(3)" of "H_(2)" at STP will have mass"=(2)/(22400)xx112=0.01g.`