Chemistry 102B- Ch. 4
Symbols in a chemical equation that detonate the physical form
(s) - Solid (g) - Gas (l) - Liquid (ppt) - Solid within a liquid (precipitate) (aq) - Aqueous
Example Formula: Al+3 O-2
- +3 - 2 = +1 (Doesn't work because it needs to equal 0) - Move the 3 in Al to the bottom of O for the number of atoms - Move the 2 to the bottom of Al for the number of atoms - Multiple 3 x 2 = 6 - Put +6 at the top of Al as the charge - Put -6 at the top of O as the charge
What is Avogadro's number?
- 6.022 x 10^23 = 1 mole of a substance - Relates to the mass of an element or compound to the number of molecules present
Arsenic compounds have been used as a poison for most of recorded history. One method for the detection of arsenic called the Marsh test was based upon the production of arsine gas (AsH3) through the following reaction: - 6 H2 + As2O3 → 2AsH3 + 3H2O - Calculate the mass of water produced in the Marsh test assuming the reaction consumes 2.72 g of As2O3
- 6H2 + As2O3 -> 2AsH3 + 3H2O - 2.72g As2O3 x 1 mol As2O3 / 197.84g As2O3 x 3 mol H2O / 1 mol As2O3 x 18.015g H2O / 1 mol H2O = 0.743g As
Combustion Reaction
- A combustion reaction is when oxygen combines with another compound to form water and carbon dioxide. - The reactions are exothermic, meaning they produce heat. - Example of Napthalene: C10H8 + 12O3 -> 10CO2 + 4H2O
Decomposition Reaction
- A decomposition reaction is the opposite of a synthesis reaction-a complex molecule breaks down to make simpler ones. - Form: AB -> A + B - Ex: Electrolysis of water to make oxygen and hydrogen gas: 2 H2O -> 2 H2 + O2
One type of Double Replacement or Metathesis: Precipitation
- A solid compound is formed from two aqueous solution. - Ex: NaCl(aq) + AgNO3(aq) -> NaNO3(aq) + AgCl(s)
Synthesis Reaction
- A synthesis reaction is when two or more simple compounds combine to form a more complicated one. - Form: A + B -> AB - Example of a synthesis reaction in the combination of Iron and Sulfur to form Iron (II) sulfide: 8Fe + S8 -> 8FeS
Second Double Replacement: Neutralization
- An acid and a base react to form a salt and water - Ex: HCl(aq) + NaOH(aq) -> NaCl(aq) + H2O(l) - Acid: HCl - Base: NaOH
Limiting Reactants
- Completely consumed; First thing consumed - When consumed, the reaction stops.
Redox (Reduction-Oxidation)
- Electrons are exchanged between atoms in the reacting compounds
Reduction
- It is the gain of electrons (RIG -> Reduction e- Gain)
Oxidation
- It is the loss of electrons (OIL -> Oxidation e- Loss)
Moles
- The coefficients in a chemical equation represent the moles of each reactant or product involved in the chemical equation. - You can create conversion factors between any reactants and products using the coefficients from the balanced reaction.
Theoretical Yield
- The maximum amount of product - Is dictated by the limiting reactant
Acid Base Reaction
- This is a special kind of double displacement reaction that takes place when an acid and base react with each other. The H+ ion in the acid reacts with the OH- ion in the base, causing the formation of water. Generally, the product of this reaction is some ionic salt and water. - Ex: Hydrobromic acid (HBr) with Sodium Hydroxide: HBr + NaOH -> NaBr + H2O
Double Displacement Reaction
- This is when the anions and cations of two different molecules switch places, forming two entirely different compounds. - Form: AB + CD -> AD + CB - Ex: Lead (II) Nitrate with Potassium iodide to form Lead (II) iodide and Potassium nitrate: Pb(NO3)2 + 2KI -> PbI2 + 2KNO3
What is a Covalent Bond?
- Two nonmetal atoms share electrons - The electron orbitals of each atom overlap
Determine the limiting reactant and the theoretical yield of Barium sulfate given that a solution containing 32.0g of Sodium sulfate is mixed with a solution containing 48.0g of Barium Nitrate - Formula: Na2SO4(aq) + Ba(NO3)2(aq) -> BaSO4(s) + 2NaNO3(aq)
1. BaSO4(s) is the product of interest. 2. 32.0g Na2SO4 x 1 mol NaSO4 / 142.04g NaSO4 x 1 mol BaSO4 / 1 mol NaSO4 x 233.39g BaSO4 / 1 mol BaSO4 = 52.6 BaSO4 48.0g Ba(NO3)2 x 1 mol Ba(NO3)2 / 261.34g Ba (NO3)2 x 1 mol BaSO4 / 1 mol Ba (NO3)2 x 233.39g BaSO4 / I mol BaSO4 = 42.9g BaSO4 Answer: BaSO4 is the limiting reactant
Determine the mass of a certain number of moles such as 2.75 moles H20
1. Calculate the molar mas of H2O - 2(1.0079 g/mol H) + (15.999 g/mol O) = 18.015 g/mol H2O 2. 2.75 mol H2O x 18.015 g H2O / 1 mol H2O = 49.5g H2O
How to convert molar mass to grams
1. Calculate the molar mass. 2. Use the molar mass to convert from moles to grams. Xmol x moles of compound / 1 mol = grams of compound
How to convert grams to molar mass
1. Calculate the number moles in the compound 2. Convert from grams moles with this formula: Xg x 1 mol x / moles of compound = molar mass compound
Steps for solving problems with a Limiting Reactant
1. Determine the product of interest 2. Convert grams of each reactant to grams of the product of interest. 3. The smaller amount calculated in step 2 is the theoretical yield of the product produced by the limiting reactant.
Determine the number of moles in the 30.00g of H2O
1. Molar mass of H2O - 2(1.0079 g/mol H) + (15.999 g/mol O) = 18.015 g/mol H2O 2. 30.00g H2O X 1 mol H2O / 18.015g H2O = 2.665 mol H2O
Naming Ionic Compounds
1. Name the Cation (Metal) - Name the element 2. Name the Anion (Nonmetal) - Name of the element with the "ide" suffix - The charge of a ion is indicated as a superscript following atomic symbol. - Several Elements on the periodic table have predictable charges.
Naming Covalent Bonds
1. Name the first element 2. Name the second element with the suffix "ide" - Include prefixes indicating the number of atoms present - The prefix mono- is excluded for the first atom.
Roman numerals
1: I 2: II 3: III 4: IV 5: V 6: VI
Standard solutions
A series of solutions of known concentrations - Comparing the absorbance of an unknown solution to the standard can determine the concentration.
How to calculate the molar mass of a compound
Add the mass of each atom found in the compound formula. - Ex: Lead (IV) oxide: PbO2 = (207.2 g/mol) + 2(15.999 g/mol) = 239.3 g/mol - (207.2 g/mol) = Molar Mass of Pb - (15.999 g/mol) = Molar Mass of Oxygen
Spectrophotometry
Based on the absorption of light by solutions - White light is passed through a prism and dispersed through the sample one wavelength at a time, producing and absorption spectrum unique to the compound present.
Name the Covalent Bond: CO
Carbon monoxide
What are the products in a chemical reaction?
Compounds formed as a result of a chemical reaction. - Found on the right side of the arrow/equation.
What are the reactants in a chemical reaction?
Compounds that react with each other - Found on the left side of the arrow/equation
How many moles of Nitrogen gas (N) will be created if 2.50 mol of KNO3 completely react according to the following equation? - 4KNO3(s) + 7Cl(s) + S(s) -> 3CO(g) + 2N2(g) K2CO3(s) + K2S(s)
Create a conversion factor using the coefficients: 4 mol KNO3 = 2 mol N2 - 2.50 mol KNO3 x 2 mol N2 / 4 mol KNO3 = 1.25 mol N2
Name the Covalent Bond: H2I
Dihydrogen Iodine
What is an ion?
Electrically charged atoms or groups of atoms.
Several Cations have multiple common charges
Examples: - Copper: * Cu +1 (Copper (I) ion) (Cuprous ion) * Cu +2 (Copper (II) ion) (Cupric ion) - Iron: * Fe +2 (Iron (II) ion) (Ferrous ion) * Fe +3 (Iron (III) ion) (Ferric ion) - Lead: * Pb +2 (Lead (II) ion) (Plumbous ion) * Pb +4 (Lead (IV) ion) (Plumbic ion) **** -ous = Lower Charge **** -ic = Higher Charge * These are all transition metals
On the periodic table, what is each column called?
Group or Family
What does the term Salt mean?
Ionic compounds that do not contain H+ or OH-
How is molar mass determined?
It is determined by expressing the atomic mass from the periodic in units grams per mole (g/mol)
What is stoichiometry?
It is the use of balanced chemical equations to answer questions like "how much"
What is stoichiometry used most for?
It is used to answer these questions: 1. How many grams of product (B) can be obtained from a certain mass of reactant (A)? 2. How many grams of reactant (B) are needed to produce a given amount of product (A)? ** A is always given and B is what you want to know it does matter whether they are reactants or products. Grams A -> Moles A -> Moles B -> Grams B
Spectrophotometer
Measures the amount of light absorbed by a sample for each wavelength of light in the spectrum
What is a coefficient?
Numbers in a chemical equation that represent how many molecules, formula units, atoms or moles of reactants or products are involved.
On the periodic table, what is each row called?
Periods, Numbered 1-7
Name the Ionic Compound: KCl
Potassium chloride
What is a compound?
Pure substances that contain two or more elements bonded together.
Balance this Equation: As2O3 + C -> As + CO
Reactants: As: 2 C: 1 -> 3 O: 3 Products: As: 1 -> 2 C: 1 -> 3 O: 1 -> 3 Balanced Equation: As2O3 + 3C -> 2As + 3CO
Balance this Equation: Na3PO4 + KOH -> NaOH + K3PO4
Reactants: Na: 3 P: 1 O: 5 -> 7 K: 1 -> 3 H: 1 -> 3 Products: Na: 1 -> 3 P: 1 O: 5 -> 7 K: 3 H: 1 -> 3 Balanced Equation: Na3PO4 + 3KOH -> 3NaOH + K3PO4
Name the Ionic Compound: NaCl
Sodium chloride
What is an Ionic Bond?
The attractive force between the cation and anion. - Between a metal and nonmetal; transfer electrons
What is molar mass?
The mass of one mole of a substance (element or compound) - Abbreviation: (mol)
The Law of Conservation of Mass
The reactants in a chemical equation must have the same number of each type of atom.
How to determine the formula of an Ionic Compound
The total charge of an ionic compound must be neutral - Positive charge (cations) = Negative charge (Anions)
How are the ions in an ionic compound held together?
They are held together in a pattern of fixed positions within a crystal structure called a crystal lattice.
How are chemical reactions used?
They are used at crime scenes or in the laboratory to identify evidence such as to screen for the presence of illegal drugs. - A positive result produces colorful compounds, indicating the presence of illegal drugs.
What do the elements in each column have in common?
They have similar properties
Single Displacement Reaction
This is when one element trades places with another element in a compound. - Form: A + BC -> AC + B - Ex: Mg replaces Hydrogen in water to Magnesium hydroxide and Hydrogen gas: Mg + 2H2O -> Mg(OH)2 + H2
Name the Covalent Bond: C3O8
Tricarbon Octaoxide
Polyatomic Ions
Two or more atoms covalently bonded together that have a net ionic charge. - Examples: * NH4 +1 - Ammonium Ion * NO3 -1 - Nitrate Ion * OH -1 - Hydroxide Ion * CN -1 - Cyanide Ion
What is an Anion and where is it located on the periodic table?
When an atom gains one or more electrons. - Negative - Found on the right side of the periodic table.
What is a cation and where is it located on the periodic table?
When an atom loses one or more electrons. - Positive - Found on the left side of the periodic table.
Monoatomic Ion
When one atom gains or loses electrons
How do you balance a chemical equation?
You add coefficients in front of each compound. 1. Rewrite the equation and leave room for coefficients 2. List the number of each type of atom in the reactants and products. 3. Balance Equation
