# Chemistry

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ASpirin, c9h8o4, is prepared by reating salicylic acid, c7h6o3, with acetic anhydride, c4h6o3, in the reaction.

c7h6o3 + c4h6o3---> c9h8o4 + c2h4o2

A student is told to prepare 45.0 g of aspirin. she is also told to use a 55.0 % excess of acetic anhydride and to expect to get an 85.0 % yield in the reaction. how many grams of each reactant should she use?

ther's one more question.

the combustion of liquid chloroethylene, c2h3cl , yields carbon dioxide, steam, hydrogen chloride gas.

-- if 25.0 g of chloroeothylene reacts with an excess of oxygen, how many grams of each product are formed.

• Chemistry -

Note that the aspirin reaction is 1:1:1:1.

1. You want to prepare 45.0 g aspirin but since the yield is only 85.0%, you must try to prepare 45.0/0.85 = about 53 g. I rounded here and there so you need to do it exactly.

2. Convert 53 g aspirin to mols. # mols = grams/molar mass. That is the number of mols of salicylic acid (SA) you need to start with. Convert to grams by #g = mols x molar mass.

3. You will need the same number of mols of acetic anhydride EXCEPT you want to add and additional 55.0% to start.

Check my thinking. Check my work. I'm bleery eyed. It's late and I've already started on this thing and erased it FOUR times.

Second problem.
1. Write and balance the equation. The products are CO2 and H2O.

2. Convert 25.0 g chloroethylene to mols. Same formula as above.

3. Using the coefficients in the balanced equation, convert mols chloroethylene to mols CO2. Do the same thing to convert mols chloroethylene to mols H2O.

4. Now convert mols CO2 to grams and mols H2O to grams. Remember that grams = mols x molar mass.

Check my work.