Question

A sample of ethane (C2H6 ) gas has the same mass as 1.5 ×1020 molecules of methane (CH4 ). How many C2H6 molecules does the sample of gas contain?
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Answer 1

Answer:

Calculation of the question

:: 6.022 x 1023 molecules of methane have mass-molar mass of methane (CH₂)

= 12 + 4x1=16g

16x1.5 x 1020

6.022 x 1023

-=398 x 10 ³g

15 x 100 molecules of methane have mass=

This is also the mass of ethane (C₂H) Molar mass of ethane (C₂H)=2 x 12+ 6x1=24+6= 30 g As 30 g of ethane has number of molecules = 6.022 x 1023

3.98 x 10 g of ethane has number of molecules = ! 6.022 x 1023 x 3.98 × 10-³

30 g = 7.99 x 10¹⁹8 x 10¹9 molecules

Answer 2

Answer:

Solution



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Correct option is A)

Mass of 1 molecule of CH4=NA16 g

Mass of 1.5×1020 molecules of methane =NA1.5×1020×16g

Mass of x molecules of C2H6 is =NA1.5×1020×16g

We know that mass of 1 molecule of C2H6=NA30g

∴ Number of molecules of ethane (x) =NA1.5×1020×16×30NA=0.8×1020