a sample of gas contains 0.1200 mol of c2h4(g) and 0.1200 mol of h2o2(g) and occupies a volume of 8.58 l. the following reaction takes place: c2h4(g) h2o2(g) ch2ohch2oh(g) calculate the volume of the sample after the reaction takes place, assuming that the temperature and the pressure remain constant.