General Chem Problem

Can anyone help me with a couple problems? Or get me started on them?

How many grams of magnesium (Mg) contain the same number of atoms as 20g of neon (Ne)?

In the reaction given below, how many grams of water are consumed if 4.0g of hydrogen gas and 32.0g of oxygen gas are produced?

2 H_2_O ----> 2 H_2_ + O_2_

*The numbers between the _'s represent subscripts.


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1) OK, 20 g of Ne is one

1) OK, 20 g of Ne is one mole, right? You don't even have to know how many atoms are in a mole (but you should know that anyway) to realize that you want 1 mole of Mg, which is (roughly) its atomic weight. Can you look that up in the periodic chart. I'm presuming your text rounds the atomic weight of Ne to 20; if not then you can create a simple ratio 20/20.179 (or whatever your textbook gives as the atomic weight of Ne) and multiple that ratio by what they give as the atomic weight of Mg. Usually they make these things simple with no annoying fractions lying around.

2) Since no matter is created or destroyed in the reaction H2O > 2H2 + O2, the same mass must be present before as after; therefore the mass of the water is same as the sum of the masses of the oxygen and the hydrogen; can you add 4 and 32?

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