chem 110 rules for solubility

Solubility Rule 1 — what and which way?

Group 1A (Li+, Na+, K+, Cs+) and ammonium (NH4+) compounds are SOLUBLE. No exceptions.

Solubility Rule 2 — what and which way?

Acetates (C2H3O2-), perchlorates (ClO4-), and nitrates (NO3-) are SOLUBLE. No exceptions.

Solubility Rule 3 — what and which way?

Most chlorides (Cl-), bromides (Br-), and iodides (I-) are SOLUBLE. Exceptions: Ag+, Hg2 2+, Hg2+, Pb2+

Solubility Rule 4 — what and which way?

Most sulfates (SO4 2-) are SOLUBLE. Exceptions: Ca2+, Sr2+, Ba2+, Ag+, Hg2 2+, Hg2+, Pb2+

Solubility Rule 5 — what and which way?

Most carbonates (CO3 2-) and phosphates (PO4 3-) are INSOLUBLE. Exceptions: Group 1A and NH4+

Solubility Rule 6 — what and which way?

Most sulfides (S2-) and hydroxides (OH-) are INSOLUBLE. Exceptions: Group 1A, NH4+, Ca2+, Sr2+, Ba2+

Which solubility rules have NO exceptions?

Rules 1 and 2 — Group 1A/ammonium, and acetate/perchlorate/nitrate. Always soluble, no thinking required.

Which rules point toward INSOLUBLE?

Rules 5 and 6 — carbonates, phosphates, sulfides, hydroxides. Rules 1-4 point toward soluble.

Which three cations are the exceptions in BOTH Rule 3 and Rule 4?

Silver, mercury, lead — Ag+, Hg2 2+, Hg2+, Pb2+

Which three cations are exceptions in BOTH Rule 4 and Rule 6?

Calcium, strontium, barium — Ca2+, Sr2+, Ba2+

Rule 4 exceptions — full list?

Ca2+, Sr2+, Ba2+ PLUS Ag+, Hg2 2+, Hg2+, Pb2+ — it borrows Rule 3's exceptions and adds three

What makes something an exception to Rule 5 or Rule 6?

Being Group 1A or ammonium. Those override everything — they are always soluble.

AgBr — soluble or insoluble?

INSOLUBLE. Rule 3, silver is an exception.

AgCl — soluble or insoluble?

INSOLUBLE. Rule 3, silver is an exception.

PbI2 — soluble or insoluble?

INSOLUBLE. Rule 3, lead is an exception.

PbBr2 — soluble or insoluble?

INSOLUBLE. Rule 3, lead is an exception.

CaSO4 — soluble or insoluble?

INSOLUBLE. Rule 4, calcium is an exception.

BaSO4 — soluble or insoluble?

INSOLUBLE. Rule 4, barium is an exception.

PbSO4 — soluble or insoluble?

INSOLUBLE. Rule 4, lead is an exception.

MgSO4 — soluble or insoluble?

SOLUBLE. Rule 4, magnesium is NOT an exception.

Na2SO4 — soluble or insoluble?

SOLUBLE. Rule 1 (sodium) wins — Group 1A is always soluble.

K2CO3 — soluble or insoluble?

SOLUBLE. Rule 5 says carbonates are insoluble, but potassium is the exception.

BaCO3 — soluble or insoluble?

INSOLUBLE. Rule 5, barium is not Group 1A or ammonium.

(NH4)3PO4 — soluble or insoluble?

SOLUBLE. Rule 5 says phosphates are insoluble, but ammonium is the exception.

Mg3(PO4)2 — soluble or insoluble?

INSOLUBLE. Rule 5, magnesium is not an exception.

Ca(NO3)2 — soluble or insoluble?

SOLUBLE. Rule 2, nitrates have no exceptions.

Fe(ClO4)3 — soluble or insoluble?

SOLUBLE. Rule 2, perchlorates have no exceptions.

Al(OH)3 — soluble or insoluble?

INSOLUBLE. Rule 6, aluminum is not an exception.

NaOH — soluble or insoluble?

SOLUBLE. Rule 6 says hydroxides are insoluble, but sodium is the exception.

Ba(OH)2 — soluble or insoluble?

SOLUBLE by Rule 6 — barium is an exception. (It dissolves poorly in real life but counts as soluble here.)

ZnS — soluble or insoluble?

INSOLUBLE. Rule 6, zinc is not an exception.

KI — soluble or insoluble?

SOLUBLE. Rule 1 (potassium) and Rule 3 both say so.

Name the six strong acids.

HCl, HBr, HI, HNO3, H2SO4, HClO4

The six strong acids — what is the 3 + 3 structure?

Three hydrohalic: HCl, HBr, HI. Three oxoacids: nitric (HNO3), sulfuric (H2SO4), perchloric (HClO4).

Which hydrohalic acid is NOT strong?

HF, hydrofluoric acid. Fluorine is the odd one out — HF is a weak acid.

Is HCN a strong or weak acid?

WEAK. It is not one of the six, so it is weak.

Is H3PO4 a strong or weak acid?

WEAK. Phosphoric acid is not one of the six.

Is acetic acid (HC2H3O2) strong or weak?

WEAK. Only about 1% of it dissociates.

Rule for acid strength?

If it is not one of the six strong acids, it is weak. No middle ground.

Are weak acids soluble?

YES. All acids, strong and weak, are soluble in water. Solubility and dissociation are different questions.

Name the six strong bases.

LiOH, NaOH, KOH, Ca(OH)2, Sr(OH)2, Ba(OH)2

The six strong bases — what is the structure?

Group 1A hydroxides (LiOH, NaOH, KOH) plus the bottom three of Group 2A (Ca, Sr, Ba).

Is Mg(OH)2 a strong or weak base?

WEAK. Magnesium is too high in Group 2A — only Ca, Sr, Ba count as strong.

Is Al(OH)3 a strong or weak base?

WEAK, and insoluble. It stays whole in ionic equations.

Is NH3 a strong or weak base?

WEAK. Ammonia and other nitrogen-containing compounds are weak bases.

Which strong bases are you NOT required to know?

RbOH, CsOH, FrOH, and Tl(OH)3 — real strong bases, but off the required list.

Oxidation Rule 1

An element in its elemental form is 0. Examples: O2, H2, Na

Oxidation Rule 2

A monatomic ion equals its charge. Examples: O2- is -2, H+ is +1, Cl- is -1

Oxidation Rule 3 and its exception

Oxygen is -2. EXCEPTION: in peroxides oxygen is -1 (H2O2)

Oxidation Rule 4 and its exception

Hydrogen is +1. EXCEPTION: in binary metal compounds hydrogen is -1 (NaH)

Oxidation Rule 5 and its exception

Halogens are -1. EXCEPTION: when the other element is a halogen ABOVE it in the periodic table, or is oxygen (BrCl3, ClO4-)

Oxidation Rule 6

Sum of oxidation numbers = 0 for a neutral compound, = the charge for a polyatomic ion.

What is the oxidation number of O in H2O2?

-1, not -2. Peroxide is the exception to Rule 3.

What is the oxidation number of H in NaH?

-1, not +1. Binary metal compound is the exception to Rule 4.

What is the oxidation number of Cl in ClO4-?

+7. Oxygen beats chlorine, so the four oxygens are -2 each (-8), and -8 + 7 = -1.

In BrCl3, which halogen is -1 and why?

Chlorine is -1 because it sits ABOVE bromine in the periodic table. Bromine comes out +3.

In IBr4+, what are the oxidation numbers?

Bromine is -1 each because it is above iodine. Four at -1 is -4, so iodine is +5.

In S2O3 2- (thiosulfate), what is each sulfur?

+2 each. Three oxygens at -2 is -6; total must be -2; so the two sulfurs share +4. This is an average.

In a complete ionic equation, what do you BREAK APART?

Only soluble ionic compounds and the six strong acids.

In a complete ionic equation, what do you LEAVE WHOLE?

Weak acids, weak bases, anything labeled (s), liquids, gases, and nonelectrolytes.

What is a spectator ion?

An ion that appears unchanged on both sides. You cross it out to get the net ionic equation.

Is an insoluble compound ever split into ions?

No. If it is (s), it stays whole in both ionic equations.

What are the four reaction types in Chapter 7?

Precipitation, acid-base (neutralization), gas evolution, and oxidation-reduction (redox).

Which four ions make a gas when they meet an acid?

Carbonate (gives CO2), sulfite (gives SO2), sulfide (gives H2S), ammonium (gives NH3).

If a gas forms, what do you call the reaction type?

Gas evolution — even though an acid-base proton transfer is happening underneath.

Oxidized vs. oxidizing agent?

Oxidized = lost electrons, number went UP. The oxidizing agent is the OTHER substance, the one that caused it (and was itself reduced).

Is the oxidizing agent an element or a whole substance?

The WHOLE substance from the reactant side, not a single element inside it.