Question

If there are 2 *10^22 c-atoms in a sample of ethane, c2h6, how many hydrogen atoms are there in that same sample

Answer 1

If a sample of ethane gas has the same mass as 1.5×10^20 molecules of methane, then how many ethane molecules does the sample gas contain?

step 1 calculation of the mass of methane

6.022 x 10 ^23 molecules of methane has mass = 16 g

1 molecule of methane has mass = 16 / 6.022 x 10 ^ 23

therefore, 1.5 x 10 ^ 20 molecules of methane has mass =

16/6.022 x 10 ^23 * 1.5 x 10 ^ 20 = 3.985 x 10 ^ -3 g

step 2 according to question the mass of 1.5 x 10 ^ 20 molecules of methane is same to the ethane .

molar mass of ethane = C2H6 = 2X 12 + 6 X 1 = 30g

step 3 calculation of molecules of ethane

30 g of ethane has molecules = 6.022 x 10 ^23

1 g of ethane has molecules = 6.022 x 10 ^ 23 / 30

so , 3.985 x 10 ^ -3 g of ethane has molecueles =

6.022 x 10 ^23 / 30 x 3.985 x 10 ^-3

0.7999 x 10 ^20 molecules of ethane

or 8.0 x 10 ^ 19 molecules