[AndyewR1]

I received this problem recently on a homework assignment, but despite working at it for quite some time I can't seem to solve it. The problem reads: "Hydrogen and Oxygen combine to form water. How many grams of Oxygen are needed to make 300 grams of water?" That is the all the information that is given to me. I would much appreciate if someone could help me out. Thanks!

[AndyewR1]

I found a way to do this problem, but I don't think it's the "correct" way. I wrote the equation, 2H2 + O2= 2H20. I then gathered that one mol O2 is 32 grams and 2 mols H2O is 36 grams. Using this knowledge, I divided 36 into 300 and got 8.33333...  . I then multiplied 8.333333 by 32 to get 266.66666 grams of Oxygen that would be necessary to make 300 grams of water. There must be a more methodical method to go about solving this problem, right?

[Borek]

266 g of oxygen is a correct answer.

It is not about "multiplying/dividing that by that", but about following the stoichiometry in a systematic way. This can be done in several ways - either using ratios or factor label method. Which one were you taught?

[AndyewR1]

266 g of oxygen is a correct answer.

It is not about "multiplying/dividing that by that", but about following the stoichiometry in a systematic way. This can be done in several ways - either using ratios or factor label method. Which one were you taught?

I was taught to do it using dimensional analysis, but I don't understand how that concept can be applied here.

[AndyewR1]

266 g of oxygen is a correct answer.

It is not about "multiplying/dividing that by that", but about following the stoichiometry in a systematic way. This can be done in several ways - either using ratios or factor label method. Which one were you taught?

I was taught to do it using dimensional analysis, but I don't understand how that concept can be applied here.

Thanks for the help everybody.

[Borek]

Would you be able to solve the problem in the opposite direction? How many grams of oxygen can be produced by the decomposition of 300 g of water?

[AndyewR1]

Would you be able to solve the problem in the opposite direction? How many grams of oxygen can be produced by the decomposition of 300 g of water?

That's actually precisely what I did.