Ch.3 - Mass Relationships in Chemical Reactions

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.3 - Mass Relationships in Chemical Reactions

Problem 74

Chapter 3, Problem 74

Assume that you have 1.39 mol of H2 and 3.44 mol of N2. How many grams of ammonia (NH3) can you make, and how many grams of which reactant will be left over?3 H2 + N2 --> NH3

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Identify the balanced chemical equation: \(3 \text{H}_2 + \text{N}_2 \rightarrow 2 \text{NH}_3\).

Determine the limiting reactant by comparing the mole ratio of \(\text{H}_2\) and \(\text{N}_2\) to the stoichiometric coefficients in the balanced equation.

Calculate the theoretical yield of \(\text{NH}_3\) in moles using the limiting reactant.

Convert the moles of \(\text{NH}_3\) to grams using the molar mass of \(\text{NH}_3\) (17.03 g/mol).

Calculate the amount of the excess reactant left over by subtracting the amount used from the initial amount.

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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 the 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 indicate that 3 moles of H2 react with 1 mole of N2 to produce 2 moles of NH3.

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. To identify the limiting reactant, we compare the mole ratios of the reactants used in the reaction to the amounts available. In this scenario, we will need to determine whether H2 or N2 limits the production of NH3.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is essential for converting between moles and grams when calculating the amounts of reactants and products. For ammonia (NH3), the molar mass is approximately 17.03 g/mol, which will be used to convert the moles of NH3 produced into grams and to determine the leftover reactants.

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