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Chapter 3: Problem 20

In chemistry, what is meant by the term "mole"? What is the importance of the mole concept?

Short Answer

Expert verified
A mole is a unit used in chemistry to measure the amount of a substance and is defined as the quantity of a substance containing approximately 6.022 x 10虏鲁 chemical entities, such as atoms, molecules, or ions. The mole concept is crucial in chemistry as it provides a bridge between the atomic/molecular and macroscopic properties of a substance, simplifying chemical calculations, establishing a relationship between mass and volume in gas laws, and allowing for comparison of quantities of different substances.

Step by step solution

01

Definition of Mole

A mole is a unit used in chemistry to measure the amount of a substance. It is defined as the quantity of a substance that contains the same number of chemical entities (atoms, molecules, ions, or other particles) as there are in 12 grams of pure carbon-12 (that is, 12g of 鹿虏C). This number of entities, also known as Avogadro's number (N鈧�), is approximately 6.022 x 10虏鲁 entities per mole.
02

Purpose of Mole Concept

The mole concept is crucial in chemistry as it provides a bridge between the atomic/molecular scale (microscopic properties) and the macroscopic properties (mass, volume, and number of particles) of a substance. This helps in carrying out calculations and conversions between these properties.
03

Importance of Mole Concept

Mole concept is essential for various reasons, including: 1. Simplifying chemical calculations: The mole concept allows chemists to convert the mass of a substance to the number of chemical entities, making it easier to balance chemical equations and calculate reactant and product quantities. 2. Establishing a relationship between mass and volume in gas laws: The mole concept helps define the molar volume of gases at constant temperature and pressure, making it easier to determine gas quantities, volumes, or concentrations in different conditions. 3. Allowing comparison of quantities: Moles make it possible to compare quantities of different substances and find equivalent quantities for chemical reactions. In conclusion, the term "mole" is a crucial unit for measuring the amount of a substance in chemistry. The mole concept enables scientists to perform calculations efficiently and establish relationships between various properties of substances. It is an indispensable tool in the field of chemistry as it simplifies calculations and allows for comparison between different substances.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Avogadro's Number
Avogadro's number is a fundamental constant in chemistry that serves as a bridge between the microscopic and macroscopic worlds. It's given by the value of approximately \(6.022 \times 10^{23}\), representing the number of chemical entities in one mole of a substance. This colossal number allows chemists to count atoms, molecules, ions, or other particles in a sample by relating it to measurable amounts like grams. It acts as a conversion factor, linking atomic mass units to grams.

With Avogadro's number, the seemingly invisible world of atoms and molecules becomes quantifiable, enabling precise calculations of chemical reactions. For example, it allows scientists to calculate how many water molecules are in a single drop or how many atoms are involved in forming a molecule when a chemical reaction takes place.
Chemical Calculations
Chemical calculations are essential for understanding the quantitative aspect of chemistry. They involve computing the amounts of reactants and products in chemical reactions. Thanks to the mole concept, these calculations become much more straightforward. By using the mole as a counting unit, chemists can reliably determine the amounts needed in reactions without getting bogged down by tiny atomic masses.

For example, when a chemical equation is balanced, it tells us the proportion of moles needed for substances to react completely. Accurately measuring amounts leads to efficient use of resources and ensures reactions reach completion as expected. Calculations often require converting between grams and moles using molar mass, which is a common task simplifying otherwise complex problems.
Molar Volume
Molar volume is particularly significant when dealing with gases. It refers to the volume occupied by one mole of a gas at a given temperature and pressure, often expressed under standard conditions (STP), which means a temperature of 0掳C and a pressure of 1 atm. At STP, the molar volume of an ideal gas is approximately 22.4 liters.

Understanding molar volume helps chemists predict and calculate how gases will behave in different scenarios. For instance:
  • It allows the determination of volume from the known number of moles or vice versa.
  • It aids in the calculation of gas densities or concentrations in solutions.
  • It helps in applying gas laws, such as the Ideal Gas Law \(PV = nRT\), where \(n\) is the number of moles.
Thus, molar volume simplifies working with gaseous substances, making chemical calculations manageable and accurate.
Chemical Equations
Chemical equations are symbolic depictions of chemical reactions, showing reactants transformed into products. They are balanced using the mole concept, ensuring that the same number of each type of atom appears on both sides of the equation.

A balanced chemical equation is crucial for accurate chemical calculations, allowing the prediction of amounts of products formed, or reactants needed. Here鈥檚 a common approach to balance equations:
  • Write down the unbalanced equation.
  • Count the number of atoms for each element on reactant and product sides.
  • Add coefficients to balance atoms, ensuring mass is conserved.
  • Adjust as necessary and check the balance by recounting atoms.
Through equations, chemists can visualize the transformation of substances, calculate stoichiometry, and understand reaction mechanisms. Balancing equations ensures that chemical reactions are described accurately and completely.

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Most popular questions from this chapter

Aspirin \(\left(\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4}\right)\) is synthesized by reacting salicylic acid \(\left(\mathrm{C}_{7} \mathrm{H}_{6} \mathrm{O}_{3}\right)\) with acetic anhydride \(\left(\mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{3}\right)\). The balanced equa- tion is $$ \mathrm{C}_{7} \mathrm{H}_{6} \mathrm{O}_{3}+\mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{3} \longrightarrow \mathrm{C}_{9} \mathrm{H}_{3} \mathrm{O}_{4}+\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2} $$ a. What mass of acetic anhydride is needed to completely consume \(1.00 \times 10^{2} \mathrm{~g}\) salicylic acid? b. What is the maximum mass of aspirin (the theoretical yield) that could be produced in this reaction?

A binary compound between an unknown element \(\mathrm{E}\) and hydrogen contains \(91.27 \% \mathrm{E}\) and \(8.73 \% \mathrm{H}\) by mass. If the formula of the compound is \(\mathrm{E}_{3} \mathrm{H}_{8}\), calculate the atomic mass of \(\mathrm{E}\).

Is there a difference between a homogeneous mixture of hydrogen and oxygen in a \(2: 1\) mole ratio and a sample of water vapor? Explain.

The following are actual student responses to the question: Why is it necessary to balance chemical equations? a. The chemicals will not react until you have added the correct mole ratios. b. The correct products will not be formed unless the right amount of reactants have been added. c. A certain number of products cannot be formed without a certain number of reactants. d. The balanced equation tells you how much reactant you need and allows you to predict how much product you'Il make. e. A mole-to-mole ratio must be established for the reaction to occur as written. Justify the best choice, and for choices you did not pick, explain what is wrong with them.

What information do we get from a chemical formula? From a chemical equation?
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