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### Topic: 2H2O exercise  (Read 2965 times)

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#### Yuniormintz

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• Mole Snacks: +0/-0 ##### 2H2O exercise
« on: March 25, 2011, 01:14:34 PM »

I really have a problem with an exercise from highschool chemic and phisic.

2H2(g)+O2(g)->2H2O(L)

a)Calculate the amounts of oxygen that react with 8 grams of hydrogen

b)the water body to be obtained

c)the volume of hydrogen will react with 10 liters of oxygen

Don't tell me the answer please, just how to do it by myself. I'm really lost =(

Sorry for the bad english, but don't know how to say some chemical terms in other laguages.

#### opti384

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« Reply #1 on: March 25, 2011, 01:18:17 PM »
When you see a chemical equation keep in mind that the ratio of coefficients is equal to the ratio of the mols of the compounds that participate in the reaction.

For example, in the given equation, 2 mols of hydrogen gas reacts with 1 mol of oxygen gas to produce 2mols of water.

So for a, how many mols of hydrogen are there in 8g of hydrogen?

#### Yuniormintz

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« Reply #2 on: March 25, 2011, 01:30:09 PM »
So.... 2 mol of H + 1 mol of O = 2 mols of water
so 8 mol of H+ 4 mol of O= 8 mols of water?

it's correct? then... that's what  the exercise wants?

If it's right, then how do I know the volume?

#### opti384

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« Reply #3 on: March 25, 2011, 01:40:25 PM »
Quote
so 8 mol of H+ 4 mol of O= 8 mols of water?

Be careful here. 1mol of hydrogen gas molecule H2 is 2g.

When the compounds that take place in the reaction are gases, the ratio of the coefficient also equals the ratio of the volume.

#### Yuniormintz

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« Reply #4 on: March 25, 2011, 02:09:23 PM »
uf, it's really hard for me to understand this from an english speaker, I'll try what you say

#### Nobby

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« Reply #5 on: March 26, 2011, 08:33:20 AM »
Use relation n =m/M  n = mole m = mass and M =molecular mass

For the burning of hydrogen you can do the following reation equation:

m(H2)/(2*M(H2)) = m(O2)/M(O2) = m(H2O/(2*M(H2O))

The number 2 is comming from the equation 2 H2 + O2 => 2 H2O