Ch.3 - Mass Relationships in Chemical Reactions

Problem 9

Chapter 3, Problem 9

If 2.00 moles of nitrogen and 5.50 moles of hydrogen are placed in a reaction vessel and react to form ammonia, what is the theoretical yield of ammonia (NH3)? (LO 3.8) N2(g) + 3 H2(g) --> 2 NH3(g)(a) 31.2 g (b) 62.3 g(c) 93.7 g (d) 34.1

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Identify the balanced chemical equation: \( N_2(g) + 3 H_2(g) \rightarrow 2 NH_3(g) \).

Determine the limiting reactant by comparing the mole ratio of \( N_2 \) and \( H_2 \) to the coefficients in the balanced equation.

Calculate the moles of \( NH_3 \) produced by the limiting reactant using stoichiometry.

Convert the moles of \( NH_3 \) to grams using the molar mass of \( NH_3 \) (17.03 g/mol).

Compare the calculated mass of \( NH_3 \) to the given options to determine the theoretical yield.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. It allows us to calculate the amounts of substances consumed and produced in a reaction based on balanced chemical equations. In this case, the stoichiometric coefficients from the balanced equation indicate the molar ratios needed to determine the theoretical yield of ammonia.

Limiting Reactant

The limiting reactant is the substance that is completely consumed first in a chemical reaction, thus determining the maximum amount of product that can be formed. In the given reaction, we need to identify whether nitrogen or hydrogen is the limiting reactant by comparing the mole ratios of the reactants to the coefficients in the balanced equation. This concept is crucial for calculating the theoretical yield of ammonia.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). To convert the number of moles of ammonia produced into grams, we must use the molar mass of ammonia (NH3), which is approximately 17.03 g/mol. This conversion is essential for expressing the theoretical yield in grams, as required by the question.

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One way to make coal burning better for the environment is to remove carbon dioxide from the exhaust gases released from power plants using a compound containing an amine (-NH2) group. The reaction between carbon dioxide and monoethanolamine is: CO2(g) + 2 HOCH2CH2NH2(aq) -> HOCH2CH2NH3 +(aq) + HOCH2CH2NHCO2-(aq) What mass of monoethanoloamine is required to react with 1.0 kg of carbon dioxide? (LO 3.5) (a) 2.8 kg(b) 1.1 kg(c) 0.93 kg(d) 0.53 kg

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Textbook Question

The diagram represents a mixture of AB2 and B2 before it reacts to form AB3. (Red spheres = A, blue spheres = B.) Which reactant is limiting, and how many AB3 molecules are formed? (LO 3.7)

(a) B2 is limiting, and 10 molecules of AB3 are formed. (b) B2 is limiting, and 4 molecules of AB3 are formed. (c) AB2 is limiting, and 6 molecules of AB3 are formed. (d) AB2 is limiting, and 4 molecules of AB3 are formed

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