Chemistry Chapter 4

Some molecular substances ___ with water when they dissolve

react

Rules to Assign Oxidation Numbers 1. Atoms in their elemental form have an oxidation number of ___ 2. The oxidation number of a ___ ion is the same as its charge

zero, monatomic

Rules to Assign Oxidation Numbers 4. The sum of the oxidation numbers in a neutral compound is ___; the sum of the oxidation numbers in a polyatomic ion is ___. (Remember to count EVERY atom, no matter how large the subscript, when assigning oxidation numbers!)

zero, the charge on the ion

What is the oxidation number of nitrogen in nitric acid, HNO3? a. +6 b. +5 c. +4 d. -1

+5

What is oxidized? What is reduced? 2Ca(s) + O₂(g) → 2CaO(s)

- Ca(s) is oxidized - O₂(g) is reduced

What are the strong acids?

- Hydrochloric Acid: HCl - Hydrobromic Acid: HBr - Hydroiodic Acid: HI - Chloric Acid: HClO₃ - Perchloric Acid: HClO₄ - Nitric Acid: HNO₃ - Sulfuric Acid (first proton): H₂SO₄

Solutions, Solvent, Solute

- Solutions: homogeneous mixtures of two or more pure substances - Solvent: present in greatest abundance - Solutes: All other substances

What is the oxidation number of nitrogen in aluminum nitride, AlN? a. +1 b. -1 c. -2 d. -3

-3

1 mL = ___ L 1 L = ___ mL 1mg = ___ g 1 g = ___ mg 1kJ = ___ J 1 J = ___ kJ

.001, 1000, .001, 1000, 1000, .001

Ways to Write Equations for Metathesis Reactions

1. Molecular equation 2. Complete ionic equation 3. Net ionic equation

How to Predict Whether a Precipitate Forms When Strong Electrolytes are Mixed

1. Note the ions present in the reactants. 2. Consider the possible cation-anion combinations. 3. Determine if any of the combinations is insoluble.

How to Complete and Balance Metathesis Equations

1. Use the chemical formulas of the reactants to determine which ions are present. 2. Write formulas for the products: cation from one reactant, anion from the other. Use charges to write proper subscripts. 3. Check your solubility rules. If either product is insoluble, a precipitate forms. 4. Balance the equation.

How to Write a Net Ionic Equation

1. Write a balanced molecular equation for the reaction. 2. Rewrite the equation to show the ions that form in solution when each soluble strong electrolyte dissociates into its ions. Only strong electrolytes dissolved in aqueous solution are written in ionic form. 3. Identify and cancel spectator ions.

___ are substances that ionize in aqueous solution to form ___

Acids, H+

What are the strong bases?

Group 1A metal hydroxides - Lithium Hydroxide: LiOH - Sodium Hydroxide: NaOH - Potassium Hydroxide: KOH - Rubidium Hydroxide: RbOH - Caesium Hydroxide: CsOH Heavy Group 2A metal hydroxides - Calcium Hydroxide: Ca(OH)₂ - Strontium Hydroxide: Sr(OH)₂ - Barium Hydroxide: Ba(OH)₂

What oxidizes what? What replaces what? 2HCl(aq) + Mg(s) → H₂(g) + MgCl₂(aq)

H+ oxidizes Mg, Mg replaces H+ Oxidation Numbers: - HCl: +1, -1 - Mg: 0 - H₂: 0 - MgCl₂: +2, -1

- Bases are substances that react with, or accept, ___ ions; they increase the concentration of ___ when dissolved in water - Substances do NOT have to contain ___ to be a base

H+, OH-, OH-

How would the volume of standard solution added change if that solution were Ba(OH)2(aq) instead of NaOH(aq)? a. Increase by one-half the volume used for titration with NaOH b. Increase by two the volume used for titration with NaOH c. Decrease by two the volume used for titration with NaOH d. Decrease by one-half the volume used for titration with NaOH

Increase by one-half the volume used for titration with NaOH

Dissociation

Ionic compounds dissolve by dissociation, where water surrounds the separated ions

In the reaction between KI(aq) and Pb(NO3)2(aq), which ions remain in solution after PbI2 precipitation is complete? a. K+ and I- b. Pb₂+ and I- c. K+ and NO₃- d. Pb₂+ and NO₃-

K+ and NO₃-

What dissolved species are present in a solution of KCN? a. H₂O(l) b. K+(aq) and H₂O(l) c. CN-(aq) d. K+(aq) and CN-(aq)

K+(aq) and CN-(aq)

Dilution The molarity of the new solution can be determined from the equation ___ x ___ = ___ x ___

Mc x Vc = Md x Vd C = concentrated D = Diluted

___ comes from a Greek word that means "to transpose."

Metathesis It appears as though the ions in the reactant compounds exchange, or transpose, ions, as seen in the given equation Mg(NO₃)₂ (aq) + 2NaOH (aq) → Mg(OH)₂ (s) + 2NaNO₃ (aq)

What dissolved species are present in a solution of NaClO4? a. H₂O(l) b. Na+(aq) and H₂O(l) c. ClO₄-(aq) d. Na+(aq) and ClO₄-(aq)

Na+(aq) and ClO₄-(aq)

Do both, just one, or neither of the following solutions conduct electricity? If just one, which one? a. NaCl(aq) only b. CH₃OH(aq) only c. Neither d. Both

NaCl (aq)

Which solute will cause the light bulb in the figure to glow most brightly, CH₃OH, NaOH, or CH₃COOH? a. CH₃OH(aq) b. NaOH(aq) c. CH₃COOH(aq) d. Cannot determine from the figure

NaOH(aq)

Do all ionic compounds dissolve in water?

No

What is the net ionic equation of this reaction? What are the spectator ions in this reaction? Pb²⁺(aq) + 2NO₃⁻(aq) + 2K⁺(aq) + 2I⁻(aq) → PbI₂(s) + 2K⁺(aq) + 2NO₃⁻(aq)

Pb²⁺(aq) + 2I⁻(aq) → PbI₂(s) K⁺, NO₃⁻

___ reactions occur when two solutions containing soluble salts are mixed and an insoluble salt is produced. The solid is called a ___

Precipitation, precipitate

Aqueous Solution

When water is the solvent, the solution is called an aqueous solution.

Electrolyte

a substance that dissociates into ions when dissolved in water

Activity Series and Hydrogen The elements ___ hydrogen will react with acids to produce hydrogen gas. Elements ___ will NOT react! A reactive metal is oxidized to a ___

above, below, cation

Ionic: - ___ are strong electrolytes - ___ are weak electrolytes - ___ are nonelectrolytes

all, none, none

In the ___ equation all strong electrolytes (strong acids, strong bases, and soluble ionic salts) are dissociated into their ions. This more accurately reflects the species that are found in the reaction mixture.

complete ionic Pb²⁺(aq) + 2NO₃⁻(aq) + 2K⁺(aq) + 2I⁻(aq) → PbI₂(s) + 2K⁺(aq) + 2NO₃⁻(aq)

Strong acids ___ dissociate in water; weak acids ___ dissociate

completely, partially

Molarity - The quantity of solute in a solution can matter to a chemist - We call the amount dissolved its ___ - ___ is one way to measure the concentration of a solution:

concentration, Molarity

Pure water ___ conduct electricity

does not Pure Water (H₂O)

A(n) ___ solution does conduct electricity

electrolyte Sodium Chloride Solution: NaCl (aq)

Metal/Acid Displacement Reactions - Elements ___ on the activity series are more reactive...They will exist as ___ - The element below will exist as the ___

higher, ions, element

Molecular compounds ___ with water, but most do NOT ___

interact, dissociate

Strong or Weak Electrolyte? 1. Is the substance ionic or molecular? If it is ___, it is a strong electrolyte. (Solubility?) 2. Molecular: is it an acid or a base? 3. If it starts with ___ or ends in ___, it is an acid. If it is NOT on the list of strong acids, it is a weak acid. (Strong acid = ___ electrolyte; weak acid = ___ electrolyte.) 4. Strong bases are ___ electrolytes; NH3 is a weak base (___ electrolyte).

ionic, H, COOH, strong, weak, strong, weak

Mixing a Solution - To create a solution of a known molarity, weigh out a known ___ (and, therefore, number of moles) of the solute. - Then add ___ to a volumetric flask, and add solvent to the line on the neck of the flask.

mass, solute

Nonelectrolyte

may dissolve in water, but it does not dissociate into ions when it does so

Strong bases dissociate to ___ ___ and ___ ___ in water; weak bases only partially react to produce ___ ___

metal cations, hydroxide anions, hydroxide anions

The ___ equation lists the reactants and products without indicating the ionic nature of the compounds. The only indication of the overall reaction is the states of matter given.

molecular Pb(NO₃)₂ (aq) + 2KCl (aq) → PbCl₂ (s) + 2KNO₃(aq)

Molarity (M) = ___/___

moles of solute, volume of solution in liters Molarity can be used as a conversion factor between moles and liters

Rules to Assign Oxidation Numbers 3. Nonmetals usually have ___ oxidation numbers, although they sometimes can be ___: - Oxygen: usually ___, except in the peroxide ion, where it is ___ - Hydrogen: usually ___ when bonded to a nonmetal and ___ when bonded to a metal - Fluorine: ___. Other halogens: usually ___, unless combined with ___ (___), where they will be positive.

negative, positive, −2, −1, +1, −1, -1, -1, oxygen, oxyanions

- To form the ___ equation, cross out anything that does not change from the left side of the equation to the right. - The ions crossed out are called ___ ions - The remaining ions are the ___ that form the product

net ionic, spectator, reactants

- Reactions between an acid and a base are called ___ reactions. - When the base is a metal hydroxide, ___ and a ___ (an ionic compound) are produced. - These equations can be written as molecular, complete ionic, or net ionic equations.

neutralization, water, salt Molecular: HCl(aq)(acid) + NaOH(aq)(base) → H₂O(l)(water) + NaCl(aq)(salt) Complete Ionic: H⁺(aq) + Cl⁻(aq) + Na⁺(aq) + OH⁻(aq) → H₂O(l) + Na⁺(aq) + Cl⁻(aq) Net Ionic: H⁺(aq) + OH⁻(aq) → H₂O(l)

A ___electrolyte does NOT dissociate in water

non

A(n) ___ solution does not conduct electricity

nonelectrolyte Sucrose Solution: C₁₂H₂₂O₁₁ (aq)

To determine if an oxidation-reduction reaction has occurred, we assign an ___ number to each element in a neutral compound or charged entity

oxidation

Oxidation-Reduction Reactions - Loss of electrons is ___ - Gain of electrons is ___ - One cannot occur without the other - The reactions are often called ___ reactions

oxidation, reduction, redox

Displacement Reactions - In displacement reactions, ions ___ an element - The ion is ___ (___) in solution.

oxidize, displaced, replaced

Because H+ consists of ONLY a proton, acids are often called ___ ___

proton donors

Neutralization Reactions with Gas Formation: - Some metathesis reactions do not give the product expected - When a carbonate or bicarbonate reacts with an acid, the products are a ___, ___ ___, and ___

salt, carbon dioxide, water CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l) NaHCO₃(aq) + HBr(aq) → NaBr(aq) + CO₂(g) + H₂O(l) Na₂S(aq) + H₂SO₄(aq) → Na₂SO₄(aq) + H₂S(g)

All substances dissolve by ___, surrounding of the ___ by the ___.

solvation, solute, solvent

Dilution A solution can be diluted by adding ONLY ___. The concentration is ___, but the ___ don't change.

solvent, lower, moles

A ___electrolyte dissociates completely when dissolved in water

strong HCl (aq) → H+ (aq) + Cl- (aq)

Molecular: - ___ are strong electrolytes - ___ are weak electrolytes - ___ are nonelectrolytes

strong acids/bases, weak acids/bases, all other compounds

- A ___ is an analytical technique in which one can calculate the concentration of a solute in a solution - A solution of known concentration, called a ___ ___ (ex: NaOH), is used to determine the unknown concentration of another solution - The reaction is complete at the equivalence point, which is based on the seen end point (___ change)

titration standard solution, color

A ___electrolyte only dissociates partially when dissolved in water

weak Its equations indicate a chemical equilibrium, where a reaction goes both forward and backward: CH3COOH (aq) ↔ H+ (aq) + CH3COO- (aq)