In a lab 178.8g of water is separated into hydrogen gas and oxygen gas. The hydrogen gas has a mass of 20.0g. What is the mass of the oxygen gas produced?

1 Answer
anor277
Nov 7, 2016

Given complete dissociation, I can automatically say that #158.8*g# of dioxygen gas were produced.

Explanation:

Of course, we could do this analytically, and write the chemical equation for water decomposition, and then apportion molar quantities:

#H_2O(l) rarr H_2(g) + 1/2O_2(g)#, but why should I bother?

ALL chemical equations conserve mass. There were approx. #180*g# of water. If this mass were decomposed and gave #20*g# dihydrogen gas, necessarily, there must be #160*g# dioxygen gas.

Would the given reaction be exothermic or endothermic? Why??

Related questions
See all questions in Separating Mixtures
Impact of this question
16145 views around the world
You can reuse this answer
Creative Commons License