Calculate the number of particles in each of the following:
(i) 46 g of Na atoms (number from mass)
(ii) `8 g O_(2)` molecules (number of molecules from mass)
(iii) 0.1 mole of carbon atoms (number from given moles)

Explanation

(i) The number of atoms
`= ("given mass")/("molar mass")xx` Avogadro number
`implies N= (m)/(M) xx N_(0)`
`implies N = (46)/(23)xx6.022 xx 10^(23)`
`implies N=12.044xx10^(23)`
(ii) The number of molecules
⇒`("given mass")/("molar mass")xx` Avogadro number
`implies N= (m)/(M)xxN_(0)`
atomic mass of oxygen = 16 u
`∴` molar mass of `O_(2)` molecules
`=16xx2=32g`
`implies N = (8)/(32)xx6. 022xx10^(23)`
`impliesN=1.5055xx10^(23)`
`~= 1.51 xx 10^(23)`
(iii) The number of particles (atom) = number of moles of particles `×` Avogadro number
`N=nxxN_(0)=0.1 xx 6.022 xx 10^(23)`
`=6.022xx10^(22)`