4g of hydrogen reacts with 20g of oxygen to form water. the mass of water formed is
Answers
Explanation:
H
2
+
2
1
O
2
⟶H
2
O
Mass-4g20g
Moles-20.625
1 mole of H
2
requires 0.5 moles of O
2
.
∴ 1.25 moles of H
2
requires 0.625 moles of O
2
∴ O
2
is a limiting reagent.
0.5 mole O
2
⟶1 mole H
2
O
∴0.625 mole O
2
=
0.5
1×0.625
moles H
2
O.
=1.25 moles of H
2
O
Therefore, mass of H
2
O formed =1.25×18=22.5 gm
Answer:
the easy answer is if you add 4 grams and 20 grams then clearly the answer is 4+20=24 grams (I think the other answer is thinking about the H2 in H2O but he has managed to get an extra 4 grams from somewhere (which you cant really do by the way)).
but using my good friend stoichiometry we can use a method that will work for other, slightly harder questions as well.
first you work out the number of moles of hydrogen, which you do by doing 4g/the molar mass of H2 (2) which means you have 2 moles.
you can then do the same thing for O2. 20/32=0.625. oh no…
we have found that there are less moles of O2 than moles of H2, meaning that we have excess hydrogen. this means that we need to balance the equation first.
2H2 + O2 → 2H20
now we know that for every 1 mole of O2 we have 2 moles of H2O. so we multiply 0.635 by 2 to get the amount of moles of water we will have.
0.625 x 2 =1.25 moles of water
so we need to work out the mass of 1.25 moles of water. the molar mass of water is 16 (O) + 2 (H2) = 18g/mol
then we do 18 x 1.25 to get 22.5g of water