The salicylic acid reactant is a white solid. Handle it as a toxic irritant. It

Question

The salicylic acid reactant is a white solid. Handle it as a toxic irritant. It will be the limiting reactant, and about 2.0-2.2 g will be weighed. The second reactant, acetic anhydride, is a liquid. It is a corrosive lachrymator and must always be kept under a fumehood. (What does the term lachrymator mean? Look it up.) Acetic anhydride is destroyed by water, so keep the reaction mixture under the fumehood until after the water is added. The amount of acetic anhydride needed for the reaction must be calculated. Assume 2.0 g of salicylic acid will be used. Calculate the moles of salicylic acid using its molar mass. Use the mole ratio from the chemical equation to determine the ideal moles of acetic anhydride. Then multiply the answer by three to obtain an excess of the acetic anhydride. Convert the moles of acetic anhydride to mass in grams using its molar mass. Convert the mass to volume in mL using the density of acetic anhydride, which is 1.082 g/mL. Finally, round the volume to the nearest 0.1 mL so it can be measured in the lab.

Explanation / Answer

1. Mass of salicylic acid used = 2.0g

Molar mass of salicylic acid = 138g/mol

Moles of salicylic acid = Mass/molar mass = 2g/138g/mol = 0.0145moles

2.from the chemical equation,1 mole of salicylic acid reacts with 1 mole of acetic anhydride.

So moles of acetic anhydride used = 0.0145moles

Excess of the acetic anhydride = 3×0.0145 = 0.0435moles

3.moles of acetic anhydride = mass/molar mass

Mass of acetic anhydride = moles × molar mass

Mass = 0.0435mol×102g/mol = 4.44g

4. Density = Mass/Volume

Volume = Mass/Density

Volume = 4.44g/1.082g/mL = 4.1mL of acetic anhydride.

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