5. Chemical Reactions Flashcards
Chemical reaction/ change
-one or more reactants are converted into one or more products
Formula weight
-sum of the atomic weights in atomic mass units (amu) of all atoms in the compound’s formula
-used for both ionic and covalent compounds
Molecular weight
-term strictly used for covalent compounds
Mole (mol)
-the formula weight of a substance expressed in grams
-formal definition: the amount of substance rhat contains as many atoms/molecules/ions as there are atoms in exactly 12g of C-12
Avogadro’s number (#23 sa calcu)
-6.02 x 10^(23) formula units per mole
-the amount of any substance that contains as many formula units as the number of atoms in 12 g of C-12
•Amadeo Avogadro
-proposed the concept of mole, but was not able to determine the number experimentally
Molar mass
-the mass of one mole of a substance expressed in grams
-formula weight of a compound expressed in grams
Combustion
-burning in air
Chemical equation
-a representation using chemical formulas of the process that occurs when reactants are converted to products
-written with the coefficients expressed as the lowest set of whole numbers
Stoichiometry
-the mass relationships in a chemical reaction
-from Greek “stoicheion” meaning element & “metron” meaning measure
Limiting reagent
-the reactant that is used up first
-the reactant that is consumed, leaving an excess of another reagents or reagents unreacted
Percent yield
-actual yield divided by the theoretical yield times 100
Actual yield
-the mass of product formed in a chemical reaction
Theoretical yield
-mass of product that should form in chemical reaction according to the stoichiometry of the balanced equation
-maximum yield
Aqueous solution
A solution in which the solvent is water
Dissociation
When ionic compound dissolve in water, cation and anions become separated from each other by water molecules
Spectator ion
-Ion that appears unchanged on both sides of a chemical equation
-did not participate in the reaction
Net ionic equation
A chemical equation that does not contain spectator ions; shows only species that actually take part in the reaction
Ions in solution react with each other only when one of these four things can happen:
- Two ions form a solid that is insoluble in water (i.e. AgCl)
- Two ions form a gas that escapes from the reaction mixture as bubbles. (i.e. NaHCO3 with HCl to form CO2)
- An acid neutralize a base
- One of the ions can oxidize another
Solubilities of ionic compounds:
Useful generalizations
- All compounds containing Na+, K+, NH4+ ions are soluble in water.
- All nitrates (NO3-) and acetates (CH3COO-) are soluble in water.
- Most chloride (Cl-) and sulfates (SO4^(-2)) are soluble in water.
•Exceptions (insoluble in water): silver chloride (AgCl), lead (II) chloride (PbCl2), mercury (I) chloride (Hg2Cl2), barium sulfate (BaSO4), and lead sulfate (PbSO4) - Most carbonates (CO3^(-2)), phosphates (PO4^(-3)), sulfides (S(-2)), and hydroxides (OH-) are insoluble in water.
•Exceptions (soluble in water): LiOH, NaOH, KOH, aqueous NH3.
Oxidation
-loss of electrons; gain of oxygen atoms or the loss of hydrogen atoms
Reduction
-gain of electrons; loss of oxygen atoms or the gain of hydrogen atoms
Oxidation-reduction reaction
-involves transfer of electrons from one species to another
Oxidizing agent
-an entity that accepts electrons in redox reaction
Reducing agent
-entity that donates electrons in redox reaction
Redox reactions that are extremely common:
1. Combustion
-compounds or mixtures that are burned are oxidized by oxygen, O2
Redox reactions that are extremely common:
2. Respiration
-the oxygen in the air we breathe oxidizes carbon-containing compounds in our cells to produce CO2 and H2O
-same lang sa combustion, but at slower and occurs at lower temperature
Redox reactions that are extremely common:
3. Rusting
-iron is oxidized to a mixture of iron oxides
Redox reactions that are extremely common:
4. Bleaching
-common bleaches are oxidizing agents
-colored compounds being bleach are usually organic compounds; oxidation converts them to colorless compounds
Redox reactions that are extremely common:
5. Batteries
-voltaic cells is a device in which electricity is generated feom chemical reaction.
Heat of reaction
-heat given off or absorbed in a chemical reaction
Exothermic reaction
-chemical reaction that gives off heat
Endothermic reaction
-chemical reaction that absorbs heat
Heat of combustion
-heat given off in a combustion reaction
Percent yield
(Actual yield / Theoretical yield) x100
Oxidation number/ oxidation state
The number of charges the atom would have in a molecule (or an ionic
compound) if electrons were transferred completely
Ionic equation
Shows dissolved species as free ions
- Redox reactions and 2. Acid-base reactions
- Transfer of electrons
- Transfer of protons
