The synthesis of urea by Frederich Wöhler in 1825 began the decline of the idea that "organic" chemicals could only be made by living organisms as part of their biological processes.
AgOCN(aq) + NH4Cl(aq) → AgCl(s) + NH2CONH2(aq)
If you perform this reaction and collect the following table of data, in which trial(s) is NH4Cl clearly the limiting reactant?
Trial mL AgOCN mL NH4Cl mass AgCl
1 10.4 mL 100.0 mL 4.9 g
2 20.2 mL 98.9 mL 10.1 g
3 30.0 mL 101.1 mL 20.6 g
4 40.2 mL 99.8 mL 30.2 g
5 50.1 mL 100.5 mL 30.1 g
6 60.2 mL 100.3 mL 30.2 g
The mL of AgOCN and NH4Cl are the initial amounts used, the mass of AgCl is how much was recovered from the reaction. (Hint: You do not need to do any calculations to answer this question.)
Look at the numbers (and we don't even know the concn AgOCN) although I assume it is constant from trial to trial. And I note the amount of NH4Cl is almost the same from trial to trial.
Trial 1 gives 4.9 g
Trial 2. more AgOCN gives more AgCl.
#3. more AgOCN gives more AgCl.
#4. more AgOCN gives more AgCl.
#5 and #6. more AgOCN does NOT give more AgCl so #5 and #6 must have NH4Cl as the limiting reagent. Right? #4 could have but we would need the concns of AgOCN and NH4Cl and make a calculation.
To determine which trials NH4Cl is the limiting reactant, we need to compare the initial amounts of AgOCN and NH4Cl used in each trial. The limiting reactant is the one that is completely consumed in the reaction and determines the maximum amount of product that can be formed.
Looking at the data provided:
Trial 1: 10.4 mL AgOCN, 100.0 mL NH4Cl
Trial 2: 20.2 mL AgOCN, 98.9 mL NH4Cl
Trial 3: 30.0 mL AgOCN, 101.1 mL NH4Cl
Trial 4: 40.2 mL AgOCN, 99.8 mL NH4Cl
Trial 5: 50.1 mL AgOCN, 100.5 mL NH4Cl
Trial 6: 60.2 mL AgOCN, 100.3 mL NH4Cl
By comparing the initial amounts of AgOCN and NH4Cl in each trial, we can see that the mL of AgOCN used increases while the mL of NH4Cl used remains relatively constant. Since the AgOCN is increasing and not reaching its maximum, the limiting reactant must be NH4Cl.
Therefore, in all trials, NH4Cl is clearly the limiting reactant.
To determine which trial(s) NH4Cl is the limiting reactant, we need to compare the amounts used to the amount of AgCl produced. The limiting reactant is the one that is completely consumed in the reaction, limiting the amount of product that can be formed.
In this reaction, AgOCN and NH4Cl react to form AgCl and NH2CONH2. The balanced chemical equation shows that the ratio of AgOCN to NH4Cl is 1:1.
Looking at the table, we can see that the mL of AgOCN used increases with each trial, while the mL of NH4Cl used does not follow a specific pattern. We need to focus on the mass of AgCl produced.
Trial 1: The mass of AgCl produced is 4.9 g.
Trial 2: The mass of AgCl produced is 10.1 g.
Trial 3: The mass of AgCl produced is 20.6 g.
Trial 4: The mass of AgCl produced is 30.2 g.
Trial 5: The mass of AgCl produced is 30.1 g.
Trial 6: The mass of AgCl produced is 30.2 g.
From the data, we can observe that the mass of AgCl increases with each trial, indicating that the amount of AgOCN used is the limiting factor in this reaction. NH4Cl is not limiting because the mass of AgCl does not change significantly with different amounts of NH4Cl.
Therefore, in all trials, NH4Cl is not the limiting reactant.