Exercises: Limiting Reactants and Percent Yield
A food truck sells sandwiches made with 2 slices of bread and 3 slices of turkey each. Use this idea to explain, in your own words, what a limiting reactant* is in a…
A food truck sells sandwiches made with 2 slices of bread and 3 slices of turkey each. Use this idea to explain, in your own words, what a limiting reactant is in a chemical reaction. Then say what an excess reactant is, and state what happens to it when the reaction stops.
Consider the balanced equation $\text{N}2(g) + 3\,\text{H}2(g) \rightarrow 2\,\text{NH}3(g)$. A reaction vessel contains 2.0 mol of $\text{N}2$ and 3.0 mol of…
Consider the balanced equation $\text{N}_2(g) + 3\,\text{H}_2(g) \rightarrow 2\,\text{NH}_3(g)$. A reaction vessel contains 2.0 mol of $\text{N}_2$ and 3.0 mol of $\text{H}_2$. Identify which reactant is limiting, and show the mole-ratio comparison that supports your answer.
In a lab, Aaliyah calculates that a reaction should produce 12.0 g of product (the theoretical yield). After she runs the experiment and dries the product, she measures…
In a lab, Aaliyah calculates that a reaction should produce 12.0 g of product (the theoretical yield). After she runs the experiment and dries the product, she measures 9.0 g. Calculate the percent yield, and state in one sentence what the percent yield tells you about the experiment.
Mateo burns magnesium in oxygen: $2\,\text{Mg}(s) + \text{O}2(g) \rightarrow 2\,\text{MgO}(s)$. He starts with 6.07 g of Mg and 4.00 g of $\text{O}2$. The molar masses…
Mateo burns magnesium in oxygen: $2\,\text{Mg}(s) + \text{O}_2(g) \rightarrow 2\,\text{MgO}(s)$. He starts with 6.07 g of Mg and 4.00 g of $\text{O}_2$. The molar masses are Mg = 24.31 g/mol, $\text{O}_2$ = 32.00 g/mol, and MgO = 40.31 g/mol. Determine the limiting reactant and calculate the theoretical yield of MgO in grams.
A student mixes 10.0 g of aluminum with excess chlorine gas: $2\,\text{Al}(s) + 3\,\text{Cl}2(g) \rightarrow 2\,\text{AlCl}3(s)$. The molar masses are Al = 26.98 g/mol…
A student mixes 10.0 g of aluminum with excess chlorine gas: $2\,\text{Al}(s) + 3\,\text{Cl}_2(g) \rightarrow 2\,\text{AlCl}_3(s)$. The molar masses are Al = 26.98 g/mol and $\text{AlCl}_3$ = 133.33 g/mol. (a) Calculate the theoretical yield of $\text{AlCl}_3$ in grams. (b) The student collects 41.5 g of $\text{AlCl}_3$. Calculate the percent yield.
Chloe reacts 5.00 g of $\text{CH}4$ with 5.00 g of $\text{O}2$ in the combustion $\text{CH}4(g) + 2\,\text{O}2(g) \rightarrow \text{CO}2(g) + 2\,\text{H}2\text{O}(g)$.…
Chloe reacts 5.00 g of $\text{CH}_4$ with 5.00 g of $\text{O}_2$ in the combustion $\text{CH}_4(g) + 2\,\text{O}_2(g) \rightarrow \text{CO}_2(g) + 2\,\text{H}_2\text{O}(g)$. The molar masses are $\text{CH}_4$ = 16.04 g/mol and $\text{O}_2$ = 32.00 g/mol. Determine which reactant is limiting, and calculate how many grams of the excess reactant remain unused when the reaction is complete.
Marcus studies the reaction $\text{Fe}2\text{O}3(s) + 3\,\text{CO}(g) \rightarrow 2\,\text{Fe}(s) + 3\,\text{CO}2(g)$. He tests three trials, each with a different mass…
Marcus studies the reaction $\text{Fe}_2\text{O}_3(s) + 3\,\text{CO}(g) \rightarrow 2\,\text{Fe}(s) + 3\,\text{CO}_2(g)$. He tests three trials, each with a different mass of reactants:
| Trial | Mass of $\text{Fe}_2\text{O}_3$ (g) | Mass of CO (g) |
|---|---|---|
| 1 | 80.0 | 42.0 |
| 2 | 80.0 | 21.0 |
| 3 | 40.0 | 42.0 |
The molar masses are $\text{Fe}_2\text{O}_3$ = 159.69 g/mol, CO = 28.01 g/mol, and Fe = 55.85 g/mol. For each trial, identify the limiting reactant and calculate the theoretical yield of iron in grams. Then explain which trial would show the greatest increase in iron produced if Marcus doubled only the mass of CO.
A chemist prepares aspirin by reacting 2.00 g of salicylic acid ($\text{C}7\text{H}6\text{O}3$, 138.12 g/mol) with 5.00 g of acetic anhydride…
A chemist prepares aspirin by reacting 2.00 g of salicylic acid ($\text{C}_7\text{H}_6\text{O}_3$, 138.12 g/mol) with 5.00 g of acetic anhydride ($\text{C}_4\text{H}_6\text{O}_3$, 102.09 g/mol) in a 1:1 mole ratio to give aspirin ($\text{C}_9\text{H}_8\text{O}_4$, 180.16 g/mol) and acetic acid. (a) Identify the limiting reactant. (b) Calculate the theoretical yield of aspirin. (c) The chemist isolates 1.85 g of aspirin. Calculate the percent yield. (d) Give two realistic reasons the actual yield is lower than the theoretical yield.