# Chemistry

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1. Hydrogen gas combines with oxygen gas to yield water. if 15 g O2 is present in the reaction, compute how much water will be produced.

2. Ten (10)grams methane gas combines with oxygen gas to form water and carbon dioxide. How much water is produced from the given reaction?

3.Twenty (20) grams carbon monoxide reacts with oxygen gas to produce carbon dioxide. Compute how much carbon dioxide is produced.

4. Calcium Carbonate decomposes into calcium oxide and carbon dioxide on the given chemical reaction below. if 25 g of carbon dioxide is produced, how much calcium carbonate is present before the reaction?

5. The reaction between hydrochloric acid and sodium hydroxide yields water and sodium chloride. If the reaction produces 50 g sodium chloride, how much HCl is present in the reaction?

• Chemistry -

These are stoichiometry problems. All are done the same way. Here is the system. (Note: Technically there will be no H2O produced without H2 and it must be an excess of H2 if you want all of the oxygen to react. I think that's what the problem wants but it doesn't say that explicitly.
1. Write and balance the equation.
2H2 + O2 ==> 2H2O

2. Convert 15g O2 to mols. mols = grams/molar mass.
15/32 = about 0.5 mol but you can do it more accurately.

3. Using the coefficients in the balanced equation, convert mols O2 to mols H2O.
0.5 mols O2 x (2 mol H2O/1 mol O2) = about 1 mol H2O (again an estimate).

4. Now convert mols H2O to grams. g = mols x molar mass
1 mol H2O x (18 g H2O/1 mol H2O) = about 18 grams H2O (an estimate).

The same system works on the others.

• Chemistry -

hey thanks...