Chp 6: Chemical Reactions
Factors affecting solubility
1. Charge on Ions 2. Size of Ions 3. How tightly ions pack together As a general rule, the greater the charge on an ion, the more tightly it sticks to oppositely charged ions.
Exceptions to solubility rules
1. Halogens (F-, Br-, Cl-, I-) are soluble Unless bonded to Ag+ or Pb2+ (silver or lead (II))
balancing equations
1. count on each side 2. only add coefficients 3. start with element with largest combo 3. or balance elemental forms last (do elements that appear in compounds first) 4. re-count https://www.webqc.org/balance.php
steps for writing ionic equation (to show dissociation of each solid as it is dissolved in water)
1. split up products into dissociated cations and anions 2. parenthesis drops out and add coefficients 3. if there were subscripts in compound add coefficients to individual elements 4. add charges 5. add phases
writing combustion equations
1. write the equation with metal first (element or compounds) + O2 (nonmetal) 2. write the charges 3. balance the equation
writing an equation for a neutralization reaction
1. write the unbalanced equation of the acid + base → water + salt (ionic compound produced by spectator ions) 2. balance the number of H+ and OH- ions that combine 3. Adding phase symbols gives us the balanced form
oxidation-reduction reaction
A chemical change in which one species loses electrons (oxidation; positive charge) while another gains electrons (reduction; negative charge; becomes ion). redox reaction
molecular equation
A chemical equation in which all ions are written as neutral compounds. show ions together as compounds
balanced equation
A chemical equation in which the number and type of atom are the same for the reactants and the products. smallest whole-number ratio (this equation tells us that 2 molecules of hydrogen react with 1 molecule of oxygen to produce 2 molecules of water.)
ionic equation for dissociation
A chemical equation that shows dissociated ions as separate species. shows dissociated ions as separate species
base
A compound that produces hydroxide ions (OH-) in aqueous solutions. Many common ones are soluble metal hydroxides which when in water, these compounds dissociate to give metal cations and hydroxide anions.
acid
A covalent compound that ionize to form hydrogen ions (H+) and a stable anion when dissolved in an aqueous solution
decomposition reaction
A reaction in which a single reactant forms two or more products. Must show charges on aqueous ions!! 1 → 2+ one splits into two or more
single displacement reaction
A reaction in which one element replaces another element in a compound. one element replaces another; knocks it out; has to have same charge to form a new ion both sides of chemical reaction have an element and a compound The starting materials are always pure elements, such as a pure zinc metal or hydrogen gas, plus an aqueous compound.
combustion reaction
A reaction in which oxygen gas combines with elements or compounds to produce oxide compounds. elemental oxygen is diatomic O2 both metals and nonmetals react with oxygen, can form ionic compounds or covalent a reaction with oxygen gas (O2)
neutralization reaction
A reaction in which the H+ from the acid reacts with the OH- from the base to form water and an ionic compound (called a salt) from the spectator ions. acid (aq) + base (aq) → water (l) + salt (aq) double displacement reactions The formation of water is the driving force for the reaction, so: --net ionic equation is H+ (aq) + OH- (aq) → H2O (l)
double displacement reaction
A reaction in which two ionic compounds swap cation-anion pairs to form two new ionic compounds. two ions replace each other; swap position; have to have same charges to form a new ion both sides of chemical reaction have two compounds make sure to write metal before nonmetal when rearranging
synthesis (combination) reaction
A reaction in which two reactants join together to form a single product; also called a combination reaction. 2 → 1 two form one
precipitate
A solid product formed from the combination of two solutions. the yellow stuff PbI2 (s) ex. NiCO3 nickel carbonate
chemical equation
A symbolic representation of a chemical change. Such equations consist of reactants and products separated by an arrow.
precipitation reaction
A type of chemical change in which two aqueous solutions combine to produce an insoluble product (s). are double displacement reactions where the anions "swap" cations (positions) the driving force is the formation of the solid. If a solid does not form, no reaction takes place.
complete and balance the equation for this single-displacement reaction AgNO3 + Al ⟶ ??? Ag: silver (+) NO3: nitrate (-) Al: aluminum (3+)
Ag and Al will swap (elements swap, not compounds Ag: silver (+) NO3: nitrate (-) Al: aluminum (3+) look at charges!! AgNO3 + Al. ⟶. Ag + AlNO3 3 AgNO3 + Al ⟶ 3 Ag + Al(NO3)3 To balance the nitrate ions, a coefficient of 3 is needed in front of the silver nitrate. To balance the silver atoms, a coefficient of 3 is needed in front of the solid silver.
net ionic equation
An equation in which the only ions shown are those directly involved in the chemical change, and spectator ions are omitted. write the two (aq) that form the one (s) with charges on reactants side and physical states on both sides *if balancing required coefficients on left, then add subscript on right of the element in compound 2Ag+(aq) + SO4^2- (aq) → Ag2SO4 (s)
complete ionic equation
An equation that shows all ions present in a solution, including the spectator ions. splits all ions apart on both sides of equation except the (s) precipitate **sometimes called "ionic equation" (without the "complete")
spectator ion
An ion that is present in a solution but not directly involved in a chemical change. Before the reaction, all four ions are present in the solution. After the reaction, lead iodide is a solid, but the other two ions, sodium and nitrate, are present in solution. In this reaction, notice that while sodium and nitrate are present, they don't actually react - they are the same before and after the reaction. These ions are present in a precipitation reaction but not directly involved.
hydrocarbons
Compounds composed of only carbon and hydrogen Fossil fuels, such as coal, oil, and natural gas are composed of these two elements. Some of the most important combustion reactions involve these two elements. The combustion reactions of fossil fuels produce most of the energy used worldwide. The combustion of coal and natural gas produces most of our electricity, and the combustion of gasoline powers most of our transportation.
Solubility Rules
Compounds containing alkali metals are always soluble. Compounds containing the ammonium ion (NH4+) are always soluble. Compounds containing the large oxyanions nitrate (NO3-), chlorate (ClO3-), perchlorate (ClO4-), or acetate (C2H3O2-), are always soluble. Compounds containing halides - fluoride, chloride, bromide and iodide are soluble, except when bonded to silver (Ag+) or lead (Pb2+). Compounds containing sulfate (SO42-) are usually soluble, except when bonded to Ba2+, Ca2+, Pb2+, or Ag+. Most other ionic compounds are insoluble. Solubility also depends on temperature: Many ionic compounds that are insoluble at room temperature become quite soluble at higher temperatures.
coefficient
In a chemical formula, the numbers written before each reactant or product to indicate the ratios in which components of the reaction are consumed or produced. written to show the smallest whole-number ratio in which molecules react used to balance chemical reactions; applied across to every element in the compound
subscript
In a chemical formula, these numbers show the number of each atom or ion present. bottom right-hand side
3 ways to show precipitation reaction
Molecular Equation: shows neutral compounds and phase symbols Complete Ionic Equation: shows all ions present; dissociated ions are separated and precipitate is a compound; write phase symbols Net Ionic Equation: only shows ions that react (precipitate); omits spectator ions (simplified the equation to the smallest whole-number coefficients.) write phase symbols
product
The compounds produced in a chemical change, shown on the right-hand side of a chemical equation.
reduction
The gain of electrons. negative charge becomes ion gains dots and write negative charge
oxidation
The loss of electrons. positive charge loses the dots and write the positive charge
reactant
The starting material in a chemical change, shown on the left-hand side of a chemical equation. aka reagent, starting material
When hydrocarbons react with oxygen, they form two main products, __________________ and ___________.
carbon dioxide water ** all hydrocarbon combustion reactions produce CO2 + H2O (hydrocarbon )+ O2 → CO2 + H2O
Some ionic compounds ___________ into cations and anions when dissolved in water.
dissociate (split apart) That is, the ions that make up the compound are pulled apart into cations and anions, and are surrounded by and stabilized by water molecules can only split apart if it's aqueous, cannot as a solid
Classifying Reactions
each type describes a different way in which reactants interact to form products 5 Types: 1. Decomposition 2. Synthesis (combination; metal + nonmetal → ionic compounds) 3. Single Displacement (elements swap, not compounds. pure element + aqueous compound → different pure element + new aqueous compound) 4. Double Displacement (elements swap, not compounds; 1. Precipitation Reactions: two soluble compounds → precipitate 2. Acid-Base Neutralization reactions: acid + base → water + salt) 5.Combustion (1. Element + Oxygen → Oxide compound 2. Hydrocarbon + Oxygen → CO2 + H2O)
magnificent 7 elements
elements that are found as diatomic molecules H2 → Hydrogen N2 → Nitrogen O2 → Oxygen F2 → Fluorine Cl2 → Chlorine Br2 → Bromine I2 → Iodine these must be written in diatomic molecule form with 2 subscript
Hydrocarbon Combustion
hydrocarbon + oxygen --> carbon dioxide (gas) + water (vapor) combustion of a hydrocarbon with oxygen produces water vapor and carbon dioxide gas produces CO2, H2O, and heat
Many ionic compounds are ________ in water.
insoluble
what forms when metals react with nonmetals?
ionic compounds
write balanced chemical equation for the reaction shown: 3CH4 + 3N2Cl4. ⟶. 3N2 + 3CCl4 + 6H2
lowest whole-number coefficients (divide by 3): CH4 + N2Cl4 → CCl4 + 2H2 + N2 carbon is written before hydrogen, if the formula contains no carbon or hydrogen atoms, then all the elements are sorted alphabetically.
write the balanced equation for the synthesis (combination) reaction of magnesium and oxygen to form magnesium oxide (MgO)
magnesium + oxygen ⟶. magnesium oxide oxygen is diatomic, so its formula is O2. Mg + O2. ⟶. MgO. (NOT BALANCED) 2Mg + O2. ⟶. 2MgO (BALANCED)
If a cation and an anion can combine to form an insoluble product, a _______________ will occur.
precipitation reaction The solubility rules are the key to predicting precipitation reactions.
Sulfur Combustion
produces sulfur oxides (SOx)
phase notation
show phase or state of reaction components (s) solid (l) liquid (water) (g) gas (aq) aqueous solution (indicates the substance is dissolved in water) H2O (l)
write the balanced equation for the decomposition of water
water ⟶ Hydrogen + Oxygen Hydrogen and oxygen are both diatomic elements, so their formulas are H2 and O2, respectively. H2O. ⟶. H2 + O2 (NOT BALANCED) 2H2O ⟶. 2H2 + O2. (BALANCED)
