Reactions in Solution and Titration

Solution

Aqueous solution (aq)

Dilute solution

Concentrated solution

Unit to express concentration. It is the amount of solute per liter of solution: Solute (in mol)/Solvet (in L).

M1V1 = M2V2, so V1=M2V2/M1 where M1 and V1 are the initial molarity and volume of the concentrated solution and M2 and V2 are the final diluted solution's molarity and volume.

When a solid is put into a liquid solvent, the attractive forces that hold the solid together come into competition with the attractive forces between the solvent molecules and the particles that ompose the solid.

Substances that dissolve in water to form solutions that conduct electricity.

• Substances that completely dissociate into ions when they dissolve in water. The solutions which result conduct electricity. They tend to be composed of ionic compounds.
• ex: Sodium chloride

Compounds that do not dissociate into ions when dissolved in water. The solutions which result do not conduct electricity. They tend to be composed of molecular compounds.`

Molecular compounds that ionize (form ions) when they dissolve in water. They produce H+ ions in aqueous solutions.

• A molecular compound that completely ionizes in solution. They are equally strong electrolytes.
• ex: Hydrochloric acid (HCl)

• Acids that do not completely ionize in water. They are weak in conducting electricity and thus make poor electrolytes.
• ex: Acetic acid (HC₂H₃O₂)

A compound which dissolves in water.

A compound which does not dissolve in water.

• Li⁺, Na⁺, K⁺, NH₄⁺, NO₃-, C₂H₃O₂-
• Cl, Br^-, and I ^- (except when paired with Ag+ Hg₂²⁺, or Pb²⁺)
• SO_4^2- (except when paired with Sr²⁺, Ba²⁺, Pb²⁺, Ag⁺, or Ca²⁺)

• OH^- and S^2-(except when paired with Li⁺, Na⁺, K⁺, NH₄⁺, Ca₂⁺, Sr²⁺, or Ba ²⁺, wherein OH^- is soluable and S^2- is slightly so)
• CO₃^2- and PO₄^3- (except when paired with Li⁺, Na⁺, K⁺, NH₄⁺)

• 1) Compounds containing the sodium ion are soluable.
• 2) Compounds containing the NO₃^- ion are soluable
• 3) When compounds containing polyatomic ions dissolve, the polyatomic ions remain as intact units as they dissolve
• 4) With some exceptions, compounds containing the CO₃^2- ion are insoluable.

Come out from

Reactions in which a solid or precipitate forms upon mixing to solutions: Soluable + Soluable -> Soluable + Insoluable. Only insoluable compounds form precipitates.

• 1) Write the formulas of the two ompounds being mixed as reactants in a chemical equation.
• 2) Below them,w rite the formula of the products that could form from the rectants. Combine the cation frm each reactant with the anion from the other.
• 3) Use the solubility rules to determine whether any of the possible products are insoluable.
• 4) If all the possible products are soluable, there will be no precipitate. Write NO REACTION.
• 5) If any possible products are insoluable, write their formula as the products of the reaction.
• 6) Balance the equation.

An equation showing the complete neutral formula for each compound in the reaction as if they existed as molecules.

Ions that do not participate in the reaction occuring in an ionic equation.

Equations which show on ly the species that actually change during the reaction.

Equations which list individually all of the ions present as either reactants or products in a chemical reaction. These show all of the speies as they are actually present in solution.

An acid reacts with a base and the two neutralize each other, producing water or, rarely, a weak electrolyte. The H⁺(aq) from the acid combines with the OH^- (aq) from the base to form H₂O (l). They generally form a salt that remains dissolved in the solution.

• Aqueous reactionns that form a gas when two solutions are mixed, resulting in bubbling. Some form a gaseous product directly when the cation of one reactant combines with the anion of another. Other form an intermediate product that then decomposes into a gas.
• Many acid-base reactions are gas-evolution reactions.

Substances that produces OH ions in aqueous solution.

H+ ion is a bare poton. Protons associate with water molecules in solution to form hydronium ions. H+ (aq) and H₃O⁺ (aq) are used interchangeably.

Acids that contain more than one ionized proton and release them sequentially

• A polyprotic acid which is strong in its first ionizable proton but weak in its second.
• ex) Sulfuric acid
• H₂SO₄ (aq) -> H^₊ (aq) + HSO₄^-

• Hydrochloric acid (HCl)
• Hydrobromic acid (HBr)
• Hydroiodic acid (HI)
• Nitric acid (HNO₃)
• Sulfuric acid (H₂SO₄)
• Perchloric acid (HClO₄)
• Acetic acid (HC₂H₃O₂) *
• Hydrofluoric acid (HF) *

* = weak

• Sodium hydroxide (NaOH)
• Lithium hydroxide (LiOH)
• Potassium hydroxide (KOH)
• Calcium hydroxide (Ca(OH)₂)
• Barium hydroxide (Ba(OH)₂)
• Ammonia (NH₃) *

* weak base. Ammonia does not contain OH-, but produces it in a reaction with water.

• H⁺(aq) + OH^-(aq) -> H₂O(l)
• Acid + Base -> Water + Salt (acid-base reactions)

Acid-base reactions generally form water and an ionic compound

Break down into component elements

• Sulfides
• No intermediate product
• Gas evolved: H₂S

• Carbonates and bicarbonates
• Intermediate product: H₂CO₃
• Gas evolved: CO₂

• Sulfites and bisulfites
• Intermediate product: H₂SO₃
• Gas evolved: SO₂

• Ammonium
• Intermediate product: NH₄OH
• Gas evolved: NH₃

• Reactions in which electrons are transferred from one reactant to the other. Many involve the reaction of a substance with oxygen, but do not necessarily need it.
• ex) A metal (which has a tendency to lose electrons) reacts wit a nonmetal (which has a tendency to gain). Metal atoms lose electrons to nonmetal atoms.

The loss of electrons

The gain of electrons (and reduction of charge).

A number given to each atom based on the electron assignments. It is the charge it would have if all shared electrons were assigned to the atom with a greater attraction for those electrons.

• 1. The oxidation state of an atom in a free element is 0.
• ex) Cu (0 ox state); Cl₂ (0 ox state)

• 2. The oxidation state of a monoatomic ion is equal to its charge.
• ex) Ca²⁺ (+2 ox state); Cl^- (-1 ox state)

• 3. The sum of the oxidation states of all atoms in a) a neutral molecule or formula unit is 0 b) an ion is equal to the charge of the ion.
• ex) H₂O 2(H ox state) + 1(O ox state) = 0
• ex) NO₃^- 1(N ox state) + 3(O ox state) = -1

• 4. In their compounds metals have positive oxidation states.
• ex) Group 1A metals always have an oxidation state of +1.
• ex) Group 2A metals always have an oxidation state of +2.

• 5. In their compounds, nonmetals are assigned oxidation states as follows:
• Fluorine +1, Hydrogen +1, Oxygen -2, Group 7A -1, Group 6A -2, Group 5A -3
• NOTE: Rules are hierarchical. If two rules conflict, consult the higher rule.

An increase in oxidation state

A decrease in oxidation state

A substance that causes the oxidation of another substance. In a redox reaction, the oxidizing agent is always reduced.

A substance that causes he reduction of another substance. In a redox reaction, the reducing agent is always oxidized.

A type of redox reaction characterized by the reaction of a substance with O₂ to form one or more oygen-containing compounds, often including water. They aways emit heat.

ex) Compounds containing carbon and hydrogen or carbon, hydrogen, and oxygen always form arbon dioxide adn water upon omplete combustion.