Unit 4 Test

chemical reactions, stoich, driving forces of reactions, kinetics, equilibrium

signs of a chemical reaction

color change, precipitate formation, gas formation, temperature change, pH change, light/fire, smell

chemical equation

describes chemical change

parts of a chemical equation

reactant(s), reaction symbol, product(s)

subscript denotes?

how many atoms of that element

coefficient denotes

how many molecules

what does a double arrow represent

reversible reaction

what does NR mean

no reaction

what does x on the arrow mean

no reaction

what does (s) mean

solid; insoluble in water

what does (aq) mean

aqueous; soluble in water

what does (l) mean

liquid

what does (g) mean

gas

a balanced equation has

the same number of each type of atom on both sides of the equation

synthesis (aka combination)

two reactants combine into one product

decomposition

one reactant breaks down into two products

single displacement

single exchange of an element

what determines if a single repacement reaction can occur

activity series; if the single cation is strong enough to kick out the other

double displacement

double exchange of an element

what determines if a double replacement reaction can occur?

the solubility of all molecules; if at least one product is insoluble and visually forms a precipitate or gas

combustion

reacting with oxygen to form CO₂ and H₂O

spectator ions

ions present in the reaction but unchanged after reaction

net ionic equations

shows only ions/molecules directly involved in the reaction

how to determine limiting reactant

find the amount of product produced from each reactant; lowest amount of product corresponds to the limiting reactant

percent yield equation

(experimental yield / theoretical yield) x 100

how to calculate enthalphy in stoich

same molar ratio format, but heat is on top instead of a product

how to predict if a reaction is spontaneous

enthalphy and entropy

change in enthalphy (\Delta H )

energy, usually in kJ/mol

what does a negative enthalphy mean

exothermic reaction

what does a positive enthalphy mean

endothermic reaction

change in entropy (\Delta S )

randomness of particles in a system

what type of enthalpy is favorable?

negative enthalphy

what type of entropy is favorable?

positive entropy

positive enthalpy and negative entropy

never spontaneous

negative enthalphy and positive entropy

always spontaneous

gibbs free energy equation

\Delta G=\Delta H-T\Delta S

negative gibbs free energy

spontaneous reaction

positive gibbs free energy

non-spontaneous reaction

collision theory

molecules must touch/collide to react with sufficient kinetic energy

low concentration of molecules

fewer collisions

high concentration of molecules

more collisions

factors affecting rate of reactions

temperature, surface area, concentration, presence of catalyst

equilibrium

state where the rate of the forward reaction is equal to the rate of the reverse reaction; constant concentration of all reactants and products; reversible reactions

equilibrium constant (K_eq)

ratio of concentration of products to concentration of reactants at equilibrium

what does it mean if K_eq is greater than 1

more products

what does it mean if K_eq is less than 1

more reactants

equilibrium constant expression

K_{eq}=\frac{\left\lbrack C\right\rbrack^{c}\cdot\left\lbrack D\right\rbrack^{d}}{\left\lbrack A\right\rbrack^{a}\cdot\left\lbrack B\right\rbrack^{b}}

le chatlier’s principle

if stress is applied to a system in equilibrium, the system changes to relieve that stress

factors that add stress to equilibrium

concentration, temperature, pressure