Ch.3 - Chemical Reactions and Reaction Stoichiometry

Brown - Chemistry: The Central Science 15th Edition

Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Not the one you use?Change textbook

Brown 15th Edition

Ch.3 - Chemical Reactions and Reaction Stoichiometry

Problem 101

Chapter 3, Problem 101

A mixture of N21g2 and H21g2 reacts in a closed container to form ammonia, NH31g2. The reaction ceases before either reactant has been totally consumed. At this stage 3.0 mol N2, 3.0 mol H2, and 3.0 mol NH3 are present. How many moles of N2 and H2 were present originally?

Verified step by step guidance

insert step 1> Write the balanced chemical equation for the reaction: N_2(g) + 3H_2(g) \(\rightarrow\) 2NH_3(g).

insert step 2> Use the stoichiometry of the reaction to set up relationships between the moles of reactants and products. For every 1 mole of N_2, 3 moles of H_2 are required to produce 2 moles of NH_3.

insert step 3> Let x be the initial moles of N_2 and y be the initial moles of H_2.

insert step 4> Set up the equations based on the stoichiometry and the information given: x - a = 3.0 (moles of N_2 remaining), y - 3a = 3.0 (moles of H_2 remaining), and 2a = 3.0 (moles of NH_3 formed).

insert step 5> Solve the system of equations to find the initial moles of N_2 (x) and H_2 (y).

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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, understanding the stoichiometric ratios of nitrogen (N2), hydrogen (H2), and ammonia (NH3) is essential to determine the original amounts of reactants.

Limiting Reactant

The limiting reactant is the substance that is completely consumed in a chemical reaction, thus determining the maximum amount of product that can be formed. In this scenario, identifying which reactant (N2 or H2) limits the formation of NH3 is crucial for calculating the initial moles of each reactant. The limiting reactant concept helps in understanding how much of each reactant was present before the reaction reached equilibrium.

Chemical Equilibrium

Chemical equilibrium occurs when the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. In this problem, the reaction between N2 and H2 to form NH3 reaches a point where the amounts of all species remain unchanged. Recognizing that the reaction has not gone to completion but has reached a state of equilibrium is vital for determining the initial amounts of N2 and H2.

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Related Practice

Textbook Question

A method used by the U.S. Environmental Protection Agency (EPA) for determining the concentration of ozone in air is to pass the air sample through a 'bubbler' containing sodium iodide, which removes the ozone according to the following equation: O31g2 + 2 NaI1aq2 + H2O1l2¡ O21g2 + I21s2 + 2 NaOH1aq2 (b) How many grams of sodium iodide are needed to remove 1.3 mg of O3?

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Textbook Question

When a mixture of 10.0 g of acetylene (C₂H₂) and 10.0 g of oxygen (O₂) is ignited, the resulting combustion reaction produces CO₂ and H₂O. (c) How many grams of C₂H₂are present after the reaction is complete?

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Textbook Question

The source of oxygen that drives the internal combustion engine in an automobile is air. Air is a mixture of gases, principally N₂(79%) and O₂(20%). In the cylinder of an automobile engine, nitrogen can react with oxygen to produce nitric oxide gas, NO. As NO is emitted from the tailpipe of the car, it can react with more oxygen to produce nitrogen dioxide gas. (b) Both nitric oxide and nitrogen dioxide are pollutants that can lead to acid rain and global warming; collectively, they are called 'NOx' gases. In 2009, the United States emitted an estimated 19 million tons of nitrogen dioxide into the atmosphere. How many grams of nitrogen dioxide is this?

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Textbook Question

The fat stored in a camel's hump is a source of both energy and water. Calculate the mass of H2O produced by the metabolism of 1.0 kg of fat, assuming the fat consists entirely of tristearin 1C57H110O62, a typical animal fat, and assuming that during metabolism, tristearin reacts with O2 to form only CO2 and H2O.

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Textbook Question

When a mixture of 10.0 g of acetylene (C₂H₂) and 10.0 g of oxygen (O₂) is ignited, the resulting combustion reaction produces CO₂ and H₂O. (c) How many grams of CO₂ and H₂O are present after the reaction is complete?

394

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