1. Calculate the moles of ASA actually obtained from the grams of product in you

Question

1. Calculate the moles of ASA actually obtained from the grams of product in your reaction.

2. Calculate the % yield.

3. Calculate the % error in your melting point, compared to the accepted one.

Weight of salicylic acid2.1g Volume of Acetic Anhydride added Buret reading initial.._16.2ml_Buret reading final_21.2ml Total volume5.00ml Drops, phosphoric acid added-drop Weight ofwatchglass+ filter paper 5422g Weight of watchglass+filter +aspirin 5607g Melt ? ?? ? ? ? ing point of aspirin. Start from 120c up to 134c

Explanation / Answer

Question 1.

The mass of acetylsalicylic acid (ASA) obtained = 56.07-54.22 = 1.85 g

The molar mass of ASA = 180 g mol-1

Therefore, the no. of moles of ASA = mass/molar mass = 1.85 g/ 180 g mol-1 = 0.01028 mol

Question 2.

The no. of moles of salicylic acid (limiting reactant) = 2.1 g/138 g mol-1 = 0.01522 mol

Now, the yield of the product = (no. of moles of product/no. of moles of limiting reactant)*100

= (0.01028/0.01522)*100

= 67.54 %

Question 3.

The accepted value for the melting point of pure aspirin = 138 to 140 oC ~ (138+140)/2 = 139 oC

The experimental value of melting point of aspirin = 120 to 134 oC ~ (120+134)/2 = 127 oC

Now, percentage error = {(experimental value - accepted value)/accepted value} * 100

= {(127 - 136)/136}*100

= -6.62 %

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