# How many grams of H2O are produced when 2.5 moles of O2 are used?

• Chemistry
• magaly79
In summary, the conversation revolves around a stoichiometry problem involving the production of H2O from 2H2 + O2 -2H2O. The question is how many grams of H2O are produced when 2.5 moles of O2 are used. The formula balances and the equation states that for every one mole of O2, 2 moles of H2O are produced. The solution involves using stoichiometric proportions and converting moles to mass. A helpful tip for approaching stoichiometry problems is to calculate the number of moles of the reacting agent and then convert it to the number of moles of the product.
magaly79
Hi I need help with a Stoichiometry problem. I am complete lost.

I don't know where to start, or how to to solve.

2H2 + O2 -2H2O. I know the formula balances and that is it.

The questions is How many grams of H2O are produced when 2.5 moles of O2 are used?

Thanks!

Well you know how many moles of 02 you have.
So in order to figure out how many moles of water this will make, you need to use the stoichiometric proportions.
The equation tells you that for every one mole of O2 you will get 2 moles of H20
so multiply 2.5 moles 02 by 2.
now, knowing you have 5 moles of H2O, calculate its mass by using the equation
moles= mass/molar mass

A hint to starting stoich problems is to always calculate your number of moles of the reacting agent, and then convert it into the number of moles of the product. From there you can answer almost any question.
Good Luck!

## 1. How do you calculate the number of grams of H2O produced?

The number of grams of H2O produced can be calculated by multiplying the number of moles of O2 used by the molar ratio of H2O to O2. In this case, the molar ratio is 2:1, so 2.5 moles of O2 would produce 5 moles of H2O. Then, using the molar mass of H2O (18.02 g/mol), we can convert the moles to grams to get a final answer of 90.1 grams of H2O produced.

## 2. Why is it necessary to use a molar ratio in this calculation?

A molar ratio is necessary because it represents the relative number of moles of each substance involved in a chemical reaction. This allows us to determine the amount of one substance produced or consumed based on the amount of another substance used.

## 3. How does the number of moles of O2 used affect the amount of H2O produced?

The number of moles of O2 used directly affects the amount of H2O produced because the reaction of O2 and H2O is a 1:2 ratio. This means that for every 1 mole of O2 used, 2 moles of H2O are produced. So, if 2.5 moles of O2 are used, 5 moles of H2O will be produced.

## 4. Is the number of grams of H2O produced always the same for a given number of moles of O2 used?

Yes, the number of grams of H2O produced will always be the same for a given number of moles of O2 used, as long as the molar ratio remains constant. This is because a chemical reaction will always produce a specific amount of product based on the reactants used, regardless of the scale or amount of the reaction.

## 5. Can this calculation be used for other chemical reactions?

Yes, this calculation can be used for other chemical reactions as long as the molar ratio between the reactants and products is known. However, the molar masses of the substances involved will differ, so the final calculation will vary depending on the specific reaction.

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