Calculation of molecular formula of hydrocarbon (REPOST)

Here, the temperature is kept constant, so we can consider the volume ratio the same as the mole ratio.
Now I want to know if my method of approach is correct or not.

Potassium hydroxide absorbs all the CO2, so we had 40 cm^3 of CO2, and therefore, X= 40

Now we can develop an equation

total volume - 20 cm^3 = volume of CO2 and H2O
(10 + 40 + y/4) - 20 = 40 + y/2
30 + y/4 = 40 + y/2
-10 = y/4
-40 = y

Now we can divide both by 10 to get:
x=4, y=-4
Therefore CxHy = C4H4

Now the problem is that why I got a negative 4?
Is my approach correct?


I have actually found a similar question answered somewhere and here is it:


My question is that why the water volume was not taken into account here?


Your responses will be much appreciated

If you measure things at room temperature the water is a liquid and hence does not have a gas volume ...

Perfectly clear.

But now this causes more problems to the above method I followed. Is it correct? I accounted for the volume of water/moles of water in my calculation, is that okay?


Posted from TSR Mobile

No, it's not ok if the measurements are taken at room temperature. You have to assume that the volume of water(g) is zero...