Question

=) Hey (=


In water the ratio of mass of hydrogen and oxygen is 1:8. Calculate the mass of water formed by heating a mixture of 5g of hydrogen and 20 gram of oxygen.

Please help me with this Thank you. ​

Answer 1

Answer:

Kindly read the whole answer I am taking you through my thought process to help you understand better

The easy answer is if you add 5 grams and 20 grams then clearly the answer is 5+20=25 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