Ionic equations are chemical equations showing the reactants and products in their ionic form in solution.
Rules for ionic equations:
1. All dissociated ions have to show the charge of that ion.
2. All elements dissociated or not have to show their state. (ie. g=gas, l= liquid, s=solid, aq=aqueous)
3. All elements and charges must be balanced.
Binary Acids - The binary compounds of hydrogen with many of the nonmetals are acidic, and in their aqueous solutions they are refered to as binary acids. To name you add the prefix hydro- and the suffix -ic to the stem of the nonmetal name, followed by the word acid.
HCl(aq) - hydrochloric acid (as a compound not in solution HCl is a gas and is called hydrogen chloride.)
H2S(aq) - hydrosulfuric acid
Oxoacids - Acids that contain hydrogen, oxygen, plus another element are called oxoacids. Oxoacids do not use the prefix hydro-. When there are 2 oxoacids, the one the larger number of Oxygens takes the suffix -ic and the one with the fewer Oxygens takes the suffix -ous.
H2SO4 - sulfuric acid
H2SO3 - sulfurous acid
HNO3 - nitric acid
HNO2 - nitrous acid
Oxoacids con't - The halogens can occur in as many as 4 oxoacids. The oxoacid with the most oxygens has teh prefix per-, and the one with the least has the prefix hypo-. These also follow the same rules for the suffix of oxoacids.
HClO4 - perchloric acid
HClO3 - chloric acid
HClO2 - chlorous acid
HClO - hypochlorous acid
Base Nomenclature - most bases are named a hydroxide of their metal.
NaOH - sodium hydroxide
When acids and bases react they produce a salt and water.
2HCl + Ca(OH)2 --> CaCl2 + 2H2O
Molarity (M) = moles of solute/liters of solution
Collectively, in a reaction where there is a transfer of elections it is called a oxidation-reduction, or redox, reaction. Where the substance loosing electron/s (e-) is being oxidized, and the substance gaining electrons is reduced.
Na --> Na+ + e- (oxidation)
Cl2 + 2e- --> 2Cl- (reduction)
Rules for assigning oxidation number:
1. The oxidation number of any free element (and element not combined chemically with a different element) is 0, regardless of how complex its molecules are.
2. The oxidation number for any simple, monatomic ion (Na+ or Cl-) is equal to the charge of the ion. The charge on a polyatomic ion can be viewed as teh net oxidation number of the ion.
3. The sum of all the oxidation numbers of teh atoms in a moecule or polyatomic ion must equal the charge on the particle.
4. In its compounds, flourine has an oxidation number of -1.
5. In its compounds, hydrogen has an oxidation number of +1.
6. In its compounds, oxygen has an oxidation number of -2.
In the formation of hydrogen chloride:
H2 + Cl2 --> 2HCl
Hydrogen is oxidized to an oxidation number of +1, and chlorine is reduced to an oxidation number of -1.
Balancing Redox Reactions: Ion-Electron Method
1.Identify the half-reactions
2.Balance each atom in the half reaction, saving H and O for last
3.Balance O by adding 1 water molecule for each needed O
4.Balance H by adding 1 H+ ion for each needed H
5.Balance charges by adding electrons to the more positive side
6.Find the least common multiple of electrons for the two half- reactions. Multiply each reaction by the factor needed to achieve the LCM of electronsAdd the half reactions, canceling like substances that appear on both sides
Balancing Basic Reactions
The simplest way to balance reactions in basic solution is to first balance them as if they were in acidic solution, then “convert” to basic solution
Additional Steps for Basic Solutions
8) To both sides of the equation, add the same number of OH- ions as there are H+.
9) Combine H+ and OH- to form H2O
10) Cancel H2O molecules that are on both sides of the reaction.
An activity series arranges metals in their ease of being oxidized (see table 5.2, pg 191). An activity series can be used to predict reations.
Na + H2O --> NaOH + H2Cu + NaOH --> no reaction
1st law of conservation of energy
Energy cannot be created or destroy; it can only be changed from one form to another.
Kenetic Energy (KE) - is the energy an object has when it's moving.
KE = 1/2mv2m = mass (kg)
v = velocity (meter/second; m/s)
Potential Energy (PE) - is the energy an object has that can be changed to kinetic energy, it can be thought of as stored energy.
The SI unit for energy is the Joule (J).
units of a joule are = kg(m/s)2 kg - kilograms
m - meter
s - seconds
Other units of energy:
calorie (cal) 1cal = 4.184J
kilocalorie (kcal) 1kcal = 1000cal = 4.184kJ
dietary Calorie is actually a kilocalorie 1Cal = 1kcal (note capital "C")
3 types of systems:
1. Open systems can gain or lose mass and energy across their boundaries.
2. Closed systems can absorb or release energy, but not mass, across the boundary.
3. Isolated systems cannot exchange matter or energy with their surroundings.
Heat gain or loss equation:
q=C x delta t
q - heat
C - heat Capacity (units of heat Capacity are J/oC
delta t - temperature change (tfinal - tinitial)
Heat Capacity depends on 2 factors: mass (m) and specific heat (s)
C = m x s
so if we substitute m x s for C in the heat gain/loss equation:
q = m x s x delta t
specific heat (s) is an intensive property indendent of sample size
units of specific heat (s) are J/goC
internal energy is a state function.
•A property whose value depends only on the present state of the system, not on the method or mechanism used to arrive at that state
•Position is a state function: both train and car travel to the same locations although their paths vary
•The actual distance traveled does vary with path
Heat transfer at constant pressure is called enthalpy (delta H)
delta H = q (at constant pressure)
delta H = Hproducts - Hreactants
(note: enthalpy is a state function)
Endothermic reactions absorb energy. Therefore, the enthalpy change (delta H) has a positive number.
Exothermic reactions lose energy, Therefore, the enthalpy change (delta H) has a negative number.
An equation that also shows the value of delta Ho is called a thermochemical equation.
N2(g) + 3H2(g) --> 2NH3(g) delta Ho = -92.38kJ
The value of delta Ho for any reaction that can be written in steps equals the sum of the values of delta Ho of each of the individual steps.
Rules for manipulating Thermochemical Equations
1. When an equation is reversed - written in the opposite direction - the sign of delta Ho must also be reversed.
2. Formulas conceled from both sides of an equation must be for the substance in identical physical states.
3. If all the coefficients of an equation are multiplied or divided by the same factor, the value of delta Ho must likewise be multiplied or divided by that same factor.
Acid Base Redox Thermo
Acids, Bases, Oxidation/Reduction (Redox) reactions and Thermochemistry