Question

How many moles of ions are contained in 1 \(\mathrm{L}\) of a 1 \(\mathrm{M}\) solution of \(\mathrm{KCl} ?\) of \(\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2} ?\)

Short answer

There are 2 moles of ions in 1 liter of 1 M KCl solution and 3 moles of ions in 1 liter of 1 M Mg(NO3)2 solution.

Step-by-step solution

- Determine the Moles of Solute

For a 1 M (molar) solution, 1 mole of solute is dissolved in 1 liter of solution. Therefore, in 1 liter of a 1 M KCl solution, there is 1 mole of KCl, and in 1 liter of a 1 M Mg(NO3)2 solution, there is 1 mole of Mg(NO3)2.

- Dissociation of KCl

KCl dissociates into K+ and Cl- ions in solution. The dissociation reaction is: KCl → K+ + Cl-. This yields 2 ions per formula unit of KCl.

- Calculate the Moles of Ions from KCl

Since 1 mole of KCl produces 1 mole of K+ and 1 mole of Cl-, the total moles of ions from 1 mole of KCl is 2 moles of ions.

- Dissociation of Mg(NO3)2

Mg(NO3)2 dissociates into Mg2+ and 2 NO3- ions in solution. The dissociation reaction is: Mg(NO3)2 → Mg2+ + 2 NO3-. This yields 3 ions per formula unit of Mg(NO3)2.

- Calculate the Moles of Ions from Mg(NO3)2

Since 1 mole of Mg(NO3)2 produces 1 mole of Mg2+ and 2 moles of NO3-, the total moles of ions from 1 mole of Mg(NO3)2 is 3 moles of ions.

Key concepts

molarity

Molarity is a fundamental concept in chemistry that helps us understand how concentrated a solution is. It's defined as the number of moles of solute per liter of solution (M). So, if you have a 1 molar (1 M) solution, this means there's 1 mole of the solute dissolved in 1 liter of the solution.

In the given exercise, we use molarity to determine how many moles of solute are present. For example, a 1 M solution of KCl means there is 1 mole of KCl in every liter of solution. This concept is crucial because it helps us calculate how substances interact in solutions. Always remember, molarity makes it easier to relate the quantities of reactants and products in chemical reactions!

dissociation

Dissociation describes the process by which an ionic compound separates into its ions when it dissolves in water. For ionic compounds, this process is straightforward but essential to grasp. Consider KCl (Potassium Chloride) and Mg(NO3)2 (Magnesium Nitrate) in our exercise.

When KCl dissolves, it dissociates into K+ and Cl- ions according to the equation:
KCl → K+ + Cl-.

This tells us that each unit of KCl results in 2 ions: one potassium (K+) and one chloride (Cl-) ion. So, 1 mole of KCl in water yields 2 moles of ions.

For Mg(NO3)2, the dissociation process involves breaking down into Mg2+ and NO3- ions as follows:
Mg(NO3)2 → Mg2+ + 2 NO3-.

This gives 1 Mg2+ ion and 2 NO3- (nitrate) ions, totaling 3 ions per formula unit. So, 1 mole of Mg(NO3)2 yields 3 moles of ions. Understanding dissociation helps predict how ionic compounds behave in solutions.

ionic compounds

Ionic compounds are made up of positive and negative ions held together by strong electrostatic forces known as ionic bonds. These compounds tend to dissociate into their constituent ions when dissolved in water.

In our exercise, KCl (Potassium Chloride) and Mg(NO3)2 (Magnesium Nitrate) are examples of ionic compounds. They consist of ions that dissociate when they interact with water, breaking into K+ and Cl- for KCl and Mg2+ and NO3- for Mg(NO3)2.

The formula of an ionic compound tells us the ratio of the ions in the compound. For instance, in KCl, there's a 1:1 ratio of potassium ions to chloride ions. In Mg(NO3)2, there is 1 magnesium ion for every 2 nitrate ions. Recognizing these ratios is essential for understanding the moles of ions produced by dissociation in solutions.

Understanding ionic compounds and their behaviors in solutions is foundational in chemistry, as it affects reactions, solubility, and the resulting properties of the solution.