Question

Which of the following represents the least number of molecues?

(a)20.0 g of H2O (18.02g/mol)
(b)77.0 g of CH4 (16.06 g/mol)
(c)68.0 g of CaH2 (42.09 g/mol)
(d)100.0 g of N2O (44.02 g/mol)
(e)84.0 g of HF (20.01 g/mol)

Answer 1

Answer: a) 20g of H2O (18.02 g/mol) molecules=6.68x10^23

Step-by-step explanation:

In order to find the amount of molecules of each of the options, we need to follow the following equation.

`molecules=(mass(g)x6.022x10^(23)(molecules/mol) )/(atomic weight(g/mol))`

So, let´s get the number of molecules for each of the options.

`a) molecules=(20(g)x6.022x10^(23)(molecules/mol) )/(18.02(g/mol))=6.68x10^(23)molecules`

`b) molecules=(77(g)x6.022x10^(23)(molecules/mol) )/(16.06(g/mol))=2.89x10^(24)molecules`

`c) molecules=(68(g)x6.022x10^(23)(molecules/mol) )/(42.09(g/mol))=9.73x10^(23)molecules`

`d) molecules=(100(g)x6.022x10^(23)(molecules/mol) )/(44.02(g/mol))=1.37x10^(24)molecules`

`d) molecules=(84(g)x6.022x10^(23)(molecules/mol) )/(20.01(g/mol))=2.53x10^(24)molecules`

the smalest number is in option a)

Best of luck.