Let the ratio of grams of hydrogen per gram of carbon in methane be M, we know that:
M = 0.3357 g / 1 g
Next, lets represent the grams of hydrogen per gram of carbon in ethane be E. The final piece of information we have is:
M / E = 4/3
If we cross multiply,
3M = 4E
Now, substituting the value of M from earlier and solving for E,
E = (3 * 0.3357) / 4
E = 0.2518
There are 0.2518 grams of hydrogen per gram of carbon in ethane.
At room temperature, number of moles of distilled water is 1 x10^-7. Hope it cleared your doubt.
As far as I know, may be wrong :When pressure is multiplied by a number, the gas volume also gets multiplied by the same number. So, the answer can be found by doing: (3.4/1.97)(12), and the answer is about 20.71.