Unit 6 Section 2: Reactions in Aqueous Solutions

Unit 6 Section 2: Reactions in Aqueous Solutions

Multiple Choice

What type of reaction occurs between an element and a compound?

Ex: Zn + 2HCl --> ZnCl₂ + H₂

• Synthesis

• Decomposition

• Single Replacement

• Double Replacement

Multiple Choice

What kind of reaction is this:
2H₂O₂ →2 H₂O + O₂

• Synthesis

• Decomposition

• Single Replacement 

• Combustion

Drag and Drop

​

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PCl₅ + ​

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H₂O → ​

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HCl + ​

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H₃PO₄

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Multiple Choice

What kind of reaction is this:
2H₂ + O₂ --> 2H₂O

• Synthesis

• Decomposition

• Single Replacement

• Double Replacement

Multiple Choice

What kind of reaction is this:
2C₃H₇OH +9O₂ -> 6CO₂ + 8H₂O

• Double Replacement

• Combustion

• Single Replacement

• Decomposition

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Al + ​

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FeO → ​

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Al₂O₂ +​

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Fe

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Multiple Choice

Based on the activity series, will this reaction occur?

Au (s) + HCl (l)

• Yes

• No Reaction

Lesson Objectives

• Explain the formation of precipitates using knowledge of solubility and intermolecular forces

• Use Evidence to Make a claim about whether a reaction will form a precipitate in a chemical reaction

Ions in Aqueous Solution

• Many double displacement reactions take place in water

• Recall: Ionic compounds are not molecules, and have slight charges

  • Have a positive end and a negative end

• When Ions are placed in water, the polar water molecules are attracted to and surround the solute ions

  • Water surrounds each individual ion, slightly separating them and allowing reactions to occur

• Dissociation: The separation of ions when an ionic compound dissolves

Showing Dissociation Equations

• We can represent Dissociation in the form of an equation that shows the ions separated in the water

  • The number of moles of each ion produced is dependent on the formula unit of the compound

Dissociation Equations Sample Problem 1

• Write the equation for the dissolution of aluminum sulfate (Al₂(SO₄)₃) in water.

  • How many moles of Aluminum ions are produced?

  • How Many moles of Sulfate ions are produced?

• Step 1: Write out the dissociation with the original compound as the "reactant" and the individual ions as "products" and balance the equation

Drag and Drop

Al₂(SO₄)₃ →​

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Al³⁺ + ​

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SO₄^2-

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Dissociation Equations Sample Problem 1

• Write the equation for the dissolution of aluminum sulfate (Al₂(SO₄)₃) in water.

  • How many moles of Aluminum ions are produced?

  • How Many moles of Sulfate ions are produced?

• Step 2: Identify how many moles of each of the ions ions are in the balanced equation

Multiple Choice

When aluminum sulfate (Al₂(SO₄)₃) is dissolved in water, how many moles of aluminum are produced?

• 1

• 2

• 3

• 4

• 5

Multiple Choice

When aluminum sulfate (Al₂(SO₄)₃) is dissolved in water, how many moles of Sulfate are produced?

• 1

• 2

• 3

• 4

• 5

Dissociation Equations Sample Problem 2

• Write the equation for the dissolution of magnesium chlorate (Mg(ClO₃)₂) in water.

  • How many moles of magnesium ions are produced?

  • How Many moles of chlorate ions are produced?

• Step 1: Write out the dissociation with the original compound as the "reactant" and the individual ions as "products" and balance the equation

Drag and Drop

Mg(ClO₃)₂ → ​

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Mg⁺ + ​

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ClO₃^-

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Multiple Choice

When Magnesium Chlorate dissociates, how many moles of magnesium ions are produced?

• 0 moles
• 1 mole
• 3 moles
• 2 moles

Multiple Choice

When Magnesium Chlorate dissociates, how many moles of chlorate ions are produced?

• 0 moles
• 1 mole
• 3 moles
• 2 moles

Solubility & Strength of Intermolecular Forces & Bonds

• The strength of intermolecular forces between water and a substance's ions affects the solubility of the substance

  • If the force between water and the individual ions is stronger than the force between the ions, the substance is soluble

• Ionic bonds are stronger than hydrogen bonds but can be overcome if there is enough solvent

  • Solvation Shells: a sphere of solvent particles that surround a solute

Precipitation Reactions

• All ionic compounds are soluble to some degree, but some are more soluble than others

  • Compounds that have a very low solubility can be considered practically insoluble

• While there are no 100% accurate rules for how ionic compounds dissolve, there are some general trends that can be used

Multiple Choice

Is Sodium Carbonate soluble or insoluble?

• Insoluble

• Soluble

Multiple Choice

Is Calcium Phosphate soluble or insoluble?

• Insoluble

• Soluble

Multiple Choice

Is lead (II) nitrate soluble or insoluble?

• soluble

• insoluble

Multiple Choice

Is iron (II) oxide soluble or insoluble?

• soluble

• insoluble

Multiple Choice

Is nickel (II) hydroxide soluble?

• soluble

• insoluble

Multiple Choice

Is copper (II) acetate soluble?

• soluble

• insoluble

Formation of a Precipitate

• Some bonds are stronger than hydrogen bonds

• When a replacement reaction creates an ionic compound with stronger bonds, it switches from aqueous to solid and forms a precipitate

  • Occurs when the attraction between the ions is greater than the attraction between the ions and surrounding water molecules

    • By looking at the solubility chart for the reactants, you can determine if the precipitate will form

Complete Ionic Equation

• Let's look at the reaction: AgNO_{3 (aq)} + NaCl _(aq) → AgCl _(s) + NaNO_{3 (aq)}

• Complete ionic equation: a chemical equation that shows the dissolved ionic compounds as free ions

  • Ag⁺ _(aq) + NO₃^- _(aq) +Na⁺ _(aq) + Cl^- _(aq)→ AgCl _(s) +Na⁺ _(aq) + NO₃^-_(aq)

    • Some of the ions in this equation don't change and are called spectator ions.

      • remain in an aqueous solution

Net Ionic Equation

• We can remove spectator ions from an equation to simplify it further

  • Ag⁺ _(aq) + NO₃^- _(aq) +Na⁺ _(aq) + Cl^- _(aq)→ AgCl _(s) +Na⁺ _(aq) + NO₃^-_(aq)

    • We can remove the sodium and chloride ions and write the equation as:

      • Ag⁺ _(aq) + Cl^- _(aq) → AgCl_(s)

• Net Ionic Equation: an equation for a reaction in solution that shows only the particles directly involved in a chemical change

Dropdown

A precipitate forms when one of the products of a ​

Select answer

replacement reaction is ​

Select answer

soluble than the reactants

Multiple Choice

The ions in an ionic equation that do not change are called

• Spectator ions

• Stationary ions

• Still ions

• Reactant ions

Multiple Choice

What kind of reaction is this:
 CaCO₃ + Ag₂SO₄ → CaSO₄ + Ag₂CO₃ 

• Decomposition

• Single Replacement

• Double Replacement

• Combustion