What Is the Limiting Reactant in the Reaction?
What is the limiting reactant if 70.0 g of C7H6O3 and 80.0 g of C4H6O3 react?
A. Water
B. Salicylic acid
C. Acetic anhydride
D. Acetylsalicylic acid
Answer : The correct option is, (B) Salicylic acid
Solution :
First we have to calculate the moles of salicylic acid and acetic anhydride.
Moles of C7H6O3 = Mass of C7H6O3 / Molar mass of C7H6O3 = 70g / 138.121g/mole = 0.507 moles
Moles of C4H6O3 = Mass of C4H6O3 / Molar mass of C4H6O3 = 80g / 102.09g/mole = 0.783 moles
Now we have to calculate the limiting and excess reagent.
The balanced chemical reaction is,
2C7H6O3(aq) + C4H6O3(aq) → 2C9H8O4(aq) + H2O(l)
From the balanced reaction we conclude that
As, 2 moles of salicylic acid react with 1 mole of acetic anhydride
So, 0.507 moles of salicylic acid react with 0.507 / 2 = 0.2535 mole of acetic anhydride
The excess of acetic anhydride = 0.783 - 0.2535 = 0.5295 moles
That means in the given balanced reaction, salicylic acid is a limiting reagent because it limits the formation of products and acetic anhydride is an excess reagent.
Hence, the limiting reagent is salicylic acid.
The reaction between salicylic acid (C7H6O3) and acetic anhydride (C4H6O3) to form acetylsalicylic acid (C9H8O4) involves a stoichiometry calculation to determine the limiting reactant. In this particular scenario with 70.0 g of salicylic acid and 80.0 g of acetic anhydride, we can identify the limiting reactant through mole calculations based on the balanced chemical equation.
By converting the given masses of salicylic acid and acetic anhydride to moles and comparing their stoichiometric ratios in the chemical equation, we can determine that salicylic acid is the limiting reagent in this reaction. This means that it will be completely consumed before all the acetic anhydride is used up, resulting in acetylsalicylic acid being produced based on the amount of salicylic acid available.
Understanding the concept of limiting reactants is crucial in predicting the extent of chemical reactions and the amount of products formed. By correctly identifying the limiting reactant, chemists can optimize reaction conditions and maximize product yield. In this case, the calculation demonstrates the importance of stoichiometry in determining reaction outcomes and highlights the significance of balanced chemical equations in chemical analysis.