Calculate the percentage of oxygen.......?

Question

When 10.00g of barium is heated in air (reacts with oxygen gas), 15.00g BaO is produced. Calculate the percentage of oxygen in Bao. Use if desired: 2 Ba+O2 => 2BaO


** can someone show me how to work this step by step?** Thank you !

Answer 1

if 15 gms = 2BaO..then..BaO= 15/2 gms
if 2Ba= 10..then Ba=5 gms
mass NEVER changes....so....amount of xygen = BaO - Ba
= 7.5-5=2.5
% of oxygen = 2.5/7.5 * 100
this is the CORRECT WAY of doing it

however because it is only %tage...so we can have a more intelligent and a better way:
total BaO = 15
Ba= 10
total O = 5
% of O = 5/ 15 *100

answer's coming to 33.33%

the answer again would be the SAME....
the trick is : total amount of oxygen/total amt of BaO * 100

hope u really understood....


edit: i wud like to add something here: we use the molecular weights ONLY if they are GIVEN in the question...they dont expect u to mug them up by rote....the above user has followed that method,but according to me,it wud be my way

Answer 2

i don't think we require the weight if BaO produced.
when you look at the formula we see that each mole of BaO has one mole of oxygen. the weight of barium oxide =137.34(weight of barium)+16(weight of oxygen)
//the atomic weights have been obtained from the log book
hence 153.34 gms of BaO has 16 gms of oxygen hence to calculate the percentage of oxygen we have to find the weight of oxygen in 100gms of BaO.
using direct ratio we will get the percentage of oxygen as 10.43%

Answer 3

It's confusing what you want to know. Do you want to know the % O in the 15 g of BaO

That's easy:

O = 16 g/mole. Ba = 137.33 g/mole

BaO = 153.33 g/mole

%O in BaO = 16/153.33 = 0.104
%Ba in BaO = 137.33/153.33 = 0.896

So out of 15 g, 89.6% will be Ba = 13.44 g
and 10.4% will be O = 1.56 g

Answer 4

barium weighs 137.33
oxygen weighs 16

% by weight is 16/137.33 = 0.1165 X 100 = 11.65 % oxygen

16 devided by 137.33 equals 11.65% oxygen