27 5.4 Limiting Reagents and Yield

Practice questions

Short-answer questions

1. Calcium nitrite [latex]\ce{Ca_{3}N_{2}}[/latex] is produced using Ca and N₂ as follows:

   [latex]\ce{3Ca + N_{2}→Ca_{3}N_{2}}[/latex]

   What is the theoretical yield of Ca₃N₂ when 120.56g of Ca is reacted with 42.87g of N₂? The atomic molar mass of Ca is 40.08g/mol, and the atomic molar mass of N is 14.01g/mol. The molar mass of Ca₃N₂ is 148.26g/mol.
   Answer: ____________ g. The answers should be rounded to 2 d.p.

2. Salicylic acid C7H6O3 reacts with acetic anhydride [latex]\ce{C_{4}H_{6}O_{3}}[/latex] in excess to form acetylsalicylic acid [latex]\ce{C_{9}H_{8}O_{4}}[/latex], which we call aspirin. The percentage yield of aspirin from the following reaction is 88.48%.

   [latex]\ce{2C_{7}H_{6}O_{3} + C_{4}H_{6}O_{3}→2C_{9}H_{8}O_{4} + H_{2}O}[/latex]

   How many grams of aspirin were actually formed by the reaction of 250.82g of salicylic acid? The molar masses of salicylic acid and acetylsalicylate acid are 138.21g/mol and \({180.16g}\), respectively.
   Answer: ____________ g. The answers should be rounded to 2 d.p.

Solutions

1. 148.75 g
2. 289.30 g