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Ch.5 - Introduction to Solutions and Aqueous Solutions
Chapter 5, Problem 27b

How many moles of KCl are contained in each solution? b. 1.8 L of a 0.85 M KCl solution

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Identify the formula for molarity: \( M = \frac{n}{V} \), where \( M \) is molarity, \( n \) is the number of moles, and \( V \) is the volume in liters.
Rearrange the formula to solve for the number of moles: \( n = M \times V \).
Substitute the given values into the equation: \( n = 0.85 \, \text{M} \times 1.8 \, \text{L} \).
Perform the multiplication to find the number of moles of KCl.
Ensure the units are consistent and the calculation is correct.

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Key Concepts

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

Molarity

Molarity (M) is a measure of concentration defined as the number of moles of solute per liter of solution. It is expressed in moles per liter (mol/L) and is crucial for calculating the amount of solute in a given volume of solution. Understanding molarity allows one to determine how many moles of a substance are present in a specific volume, which is essential for stoichiometric calculations in chemistry.
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Moles

A mole is a fundamental unit in chemistry that quantifies the amount of substance. One mole contains approximately 6.022 x 10²³ entities, such as atoms or molecules, known as Avogadro's number. Moles provide a bridge between the atomic scale and macroscopic quantities, allowing chemists to relate mass, volume, and concentration in chemical reactions and solutions.
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Volume and Concentration Relationship

The relationship between volume and concentration is critical in determining the amount of solute in a solution. The formula used is: moles of solute = molarity (M) × volume (L). This relationship allows for the calculation of moles when the molarity and volume of a solution are known, facilitating various applications in laboratory settings and chemical reactions.
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Relationship of Volume and Moles Example