Ok I'm not sure about this ,but I think that’s how it works :

First you find out what is 1 mole of each :

1 mole of N2O = (14*2) + 16 = 44 g

1 mole of CCl3F = 12+ (35 * 3) + 19 = 136 g

Now if 1 mole of CCl3F has 136 g then what number of moles contains 3 g ? Cross multiplication :

1 mole : 136g

X moles : 3 g

Divide 3/136 = 0.022 moles

Now if 0.022 moles of CCl3F contains 3 g the same number of molecules of N2O should =

0.022 * 44 g = 0.968 g

So, I would go with (g) which is the closest : 0.961 g

Hope that helps………….

First you find out what is 1 mole of each :

1 mole of N2O = (14*2) + 16 = 44 g

1 mole of CCl3F = 12+ (35 * 3) + 19 = 136 g

Now if 1 mole of CCl3F has 136 g then what number of moles contains 3 g ? Cross multiplication :

1 mole : 136g

X moles : 3 g

Divide 3/136 = 0.022 moles

Now if 0.022 moles of CCl3F contains 3 g the same number of molecules of N2O should =

0.022 * 44 g = 0.968 g

So, I would go with (g) which is the closest : 0.961 g

Hope that helps………….