Question

Which sample of gas contains the FEWEST molecules?

`1.` `"A 4.4 g mass of carbon dioxide."`
`2.` `"A 3.4 g mass of ammonia."`
`3.` `"A 1.6 g mass of methane."`
`4.` `"A 3.2 g mass of sulfur dioxide."`

Answer 1

`"Sample 4"`, `"sulfur dioxide."`

Explanation:

All we need to do is to calculate the molar quantity of each gas, and we know that `1*mol` of any substance constitutes `6.022xx10^23` individual particles of that substance.........

`"Moles of"` `CO_2=(4.4*g)/(44.01*g*mol^-1)=0.1*mol`.

`"Moles of"` `NH_3=(3.4*g)/(17.01*g*mol^-1)=0.2*mol`.

`"Moles of"` `CH_4=(1.6*g)/(16.04*g*mol^-1)=0.1*mol`.

`"Moles of"` `SO_2=(3.2*g)/(64.1*g*mol^-1)=0.05*mol`.

Since the molar quantity represents an actual number, `N_A=6.022xx10^23*mol^-1`, clearly, there are FEWER `"sulfur dioxide"` molecules than the number of molecules of any other gas. In other words, since `SO_2(g)` is the heaviest, the given mass contains the least number of molecules.