Ch.3 - Chemical Reactions and Reaction Stoichiometry

Problem 62a

Chapter 3, Problem 62a

The reaction between potassium superoxide, KO2, and CO2, 4 KO2 + 2 CO2¡2K2CO3 + 3 O2 is used as a source of O2 and absorber of CO2 in selfcontained breathing equipment used by rescue workers. (a) How many moles of O2 are produced when 0.400 mol of KO2 reacts in this fashion?

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Identify the balanced chemical equation: \(4 \text{ KO}_2 + 2 \text{ CO}_2 \rightarrow 2 \text{ K}_2\text{CO}_3 + 3 \text{ O}_2\).

Determine the mole ratio between KO2 and O2 from the balanced equation. The ratio is 4 moles of KO2 to 3 moles of O2.

Set up a proportion using the mole ratio to find the moles of O2 produced from 0.400 moles of KO2.

Calculate the moles of O2 by multiplying 0.400 moles of KO2 by the ratio \(\frac{3 \text{ moles O}_2}{4 \text{ moles KO}_2}\).

Simplify the expression to find the moles of O2 produced.

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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 amount of substances consumed and produced in a reaction based on balanced chemical equations. In this case, the stoichiometric coefficients from the balanced equation indicate how many moles of O2 are produced per mole of KO2 reacted.

Mole Concept

The mole concept is a fundamental principle in chemistry that defines the amount of substance. One mole corresponds to 6.022 x 10^23 entities (atoms, molecules, etc.). This concept is crucial for converting between the number of moles and the mass or volume of a substance, enabling calculations of how many moles of O2 can be generated from a given amount of KO2.

Balanced Chemical Equation

A balanced chemical equation represents a chemical reaction with equal numbers of each type of atom on both sides of the equation. It provides the ratios of reactants and products involved in the reaction. In the given reaction, the coefficients indicate that for every 4 moles of KO2, 3 moles of O2 are produced, which is essential for determining the amount of O2 generated from the specified amount of KO2.

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Washing soda, a compound used to prepare hard water for washing laundry, is a hydrate, which means that a certain number of water molecules are included in the solid structure. Its formula can be written as Na2CO3 # xH2O, where x is the number of moles of H2O per mole of Na2CO3. When a 2.558-g sample of washing soda is heated at 125 C, all the water of hydration is lost, leaving 0.948 g of Na2CO3. What is the value of x?

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Textbook Question

Hydrofluoric acid, HF(aq), cannot be stored in glass bottles because compounds called silicates in the glass are attacked by the HF(aq). Sodium silicate (Na₂SiO₃), for example, reacts as follows: Na₂SiO₃(s) + 8 HF(aq) → H₂SiF₆(aq) + 2 NaF(aq) + 3 H₂O(l) (a) How many moles of HF are needed to react with 0.300 mol of Na₂SiO₃? (b) How many grams of NaF form when 0.500 mol of HF reacts with excess Na₂SiO₃? (c) How many grams of Na₂SiO₃can react with 0.800 g of HF?

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Textbook Question

The reaction between potassium superoxide, KO2, and CO2, 4 KO2 + 2 CO2¡2K2CO3 + 3 O2 is used as a source of O2 and absorber of CO2 in selfcontained breathing equipment used by rescue workers. (b) How many grams of KO2 are needed to form 7.50 g of O2?

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Textbook Question

Several brands of antacids use Al1OH23 to react with stomach acid, which contains primarily HCl: Al(OH)₃(s) + HCl(aq) → AlCl₃(aq) + H₂O(l) (b) Calculate the number of grams of HCl that can react with 0.500 g of Al(OH)₃. (c) Calculate the number of grams of AlCl₃ and the number of grams of H₂Oformed when 0.500 g of Al(OH)₃ reacts.

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Textbook Question

An iron ore sample contains Fe₂O₃together with other substances. Reaction of the ore with CO produces iron metal: Fe₂O₃(s) + CO(g) → Fe(s) + CO₂(g) (b) Calculate the number of grams of CO that can react with 0.350 kg of Fe₂O₃. (c) Calculate the number of grams of Fe and the number of grams of CO₂ formed when 0.350 kg of Fe₂O₃ reacts.

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