In 450g of water in how many hydrogen elements and how many oxygen elements? Find...
Answers
Answer:
Explanation:
I'll show you two approaches to solving this problem, one really short and one relatively long.
.
SHORT VERSION
The problem tells you that
6 g
of hydrogen gas,
H
2
, react with an unknown mass of oxygen gas,
O
2
, to form
54 g
of water.
As you know, the law of mass conservation tells you that the in a chemical reaction the total mass of the reactants must be equal to the total mass of the products.
In your case, this can be written as
total mass of reactants
m
H
2
+
m
O
2
=
mass of product
m
H
2
O
This means that the reaction must have consumed
m
O
2
=
m
H
2
O
−
m
H
2
m
O
2
=
54 g
−
6 g
=
48 g O
2
.
LONG VERSION
You can get the same result by using a bit of stoichiometry. First, write a balance d chemical equation for this reaction
2
H
2(g]
+
O
2(g]
→
2
H
2
O
(g]
Notice that you have a
2
:
1
mole ratio between water and oxygen gas. This means that the reaction will produce twice as many moles of water as you have moles of oxygen taking part in the reaction.
Use water's molar mass to determine how many moles of water were produced
54
g
⋅
1 mole H
2
O
18.015
g
=
2.998 moles H
2
O
This means that the reaction consumed
2.998
moles H
2
O
⋅
1 mole O
2
2
moles H
2
O
=
1.499 moles O
2
Finally, use oxygen gas' molar mass to find how many grams would contain this many moles
1.499
moles O
2
⋅
32.0 g
1
mole O
2
=
48 g
Once again, the answer will be
48 g
of oxygen gas.