# How many grams of water are made from the reaction of 4.0 grams of hydrogen gas? Given: 2H2 + O2 > 2H2O?

**Answer:**

no of moles of h2 gas

4/2 = 2mol

2mol of h2o are produced

2= x / 18

x= 36 g

Could be wrong, took this way back in highschool/1year college

Molecular mass (Mr) of H2 = 2

Therefore, Moles of H2 = Mass/Mr = 4/2 = 2

Molar ratio = 2 moles of H2 with one mole of O2.

Atomic mass of oxygen = 16

Therefore molecular mass of O2 = 16 x 2 = 32

As 2 moles of hydrogen react with one mole of oxygen, 4 g of H2 reacts with 32 g of O2 to form 32 + 4 = 36 g of water.

Alternatively, since 2 moles of H2 react with one mole of oxygen to produce 2 moles of water, 4 g oh H2 produces 2 moles of water.

Molar mass of water = 2 + 16 = 18

Therefore, mass of two moles of water = 18 x 2

Therefore, mass of water formed frome 4 g (2 moles) of H2 is 36 grams.

First, you need to use the molecular weight of H2, which would be 2.0016 g.

Then, from the balanced equation, you know that the ratio is 1:1 for H2 and H2O. Therefore, for every 2 moles of H2, you get 2 moles of H2O. Now, you do the math, but here is the answer:

4.0g H2 x (I mol H2 / 2.0016g H2) x (2 mol H2O / 2 mol H2) x (18.006g H2O / 1 mol H2O)=

In other words:

4x18.006 / 2.0016 g H2O.

36 grams of water.

(4 g H2) x (1 mole H2 / 2 g H2) x (1 mole H2O / 1 mole H2) x (18 g H2O / 1 mole H2O) = 36 g H2O

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