Question

A cylinder containing CH4, C2H6, and N2 has to be prepared in which the ratio of the moles of CH4 to C2H6 is 1.3 to 1. Available are (1) a cylinder containing a mixture of 70% N2 and 30% CH4, (2) a cylinder containing a mixture of 90% N2 and 10% C2H6, and a cylinder of pure N2. Determine the proportions in which the respective gases from each cylinder should be used.

Answer 1

In given cylinder CH4 : C2H6 moles ratio is 1.3:1 required ,

volume is proportional to moles of gas

If we take 1 Liter of cylinder 2 we get 0.9 L of N2 and 0.1 L C2H6

volume of CH4 required = 1.3 times C2H6 volume = 1.3 x 0.1 = 0.13 L

volume of gas from cylinder 1 required = ( 100/30) x 0.13 L = 0.433 L

Thus for 0.433 Liters of Cylinder 1 we take 1 Liter of cylinder 2   and mix them , if we need additional gas to fill in cylinder we can use N2 from pure N2 cylinder.