unit 6 Flashcards
solution
homogeneous mixture of 2 substances
solvent
majority component of a solution
aqueous solution
a solution where water acts as a solvent
solute
minority component of a mixture
dilute solution
small amount of solute dissolved in the solvent
concentrated solution
large amount of solute dissolved in the solvent
saturated solution
a solution in which the solution is in equilibrium with the undissolved state
unsaturated solution
has less than the maximum amount of solute dissolved in the solvent
supersaturated solution
more than the maximum amount of solute is dissolved
can be obtained by preparing a saturated solution at a high temperature, then cooled carefully to avoid crystallizing the excess solute
metastable
in a saturated solution, excess solute will crystallize if the solution is shaken or if a seed crystal is added to start crystallization
concentration
expression of solute : solvent in a solution and is often expressed as amount of solute per volume of solution
molarity
the number of moles of solute per liter of solution
molar concentration conversion factors
1.5 mol x = 1 L x soln
1.5 mol x / 1 L x soln
1 L x soln / 1.5 mol x
ratios are just for example*
standard solution
solution of a known concentration
stock solution
solutions stored in concentrated forms
formula used in dilution problems
m1v1 = m2v2
m1: concentration of stock solution
v1: volume of stock solution
m2: concentration of desired solution
v2: volume of desired solution
entropy
measure of energy randomization or dispersal in a system
how does entropy work?
-gases have kinetic energy due to particle motion
-when barrier is removed, each gas and its kinetic energy is dispersed
-the gas mixture has a greater energy dispersal than the separated components
steps of dissolving
- energy is used to break attractions between solvent particles
- energy is used to break attractions between solute particles
- energy is released when new attractions are formed between solvent and solute particles, energy is used as heat
-when the energy released is less than the energy used, the shortfall is compensated by the increased entropy of the solution
entropy strength when dissolved: solids
greatest increase
entropy strength when dissolved: liquids
moderate increase
entropy strength when dissolved: gases
no increase
lattice energy
energy needed to disrupt the crystal
-very strong
-lattice breaking should not occur
why do strong electrolyte solutions conduct electricity strongly?
-ionic substances dissociate completely into ions when dissolved in water
-some molecular compounds ionize when dissolved in water
ionization
molecule breaks apart into ions
why do weak electrolyte solutions conduct electricity weakly?
-other compounds dissociate/ionize less than 10%
-most common are weak acids and weak bases
why do nonelectrolyte solutions not conduct electricity?
molecular compounds are soluble in water, but form no compounds
dynamic equillibrium
rate of dissolving = rate of crystallization
how do you show equillibrium in a chemical equation?
double arrow
proportion of solubility (solids) to temperature
directly proportional
proportion of temperature to entropy (solids/liquids)
directly proportional
the solubility of a gas in a liquid is affected by:
temperature and pressure
proportion of solubility (gases) and temperature
inversely proportional
proportion of solubility (gases) and pressure
directly proportional
higher pressure of gas above a liquid = more soluble the gas is
Henry’s law
quantifies the solubility of gases with increasing pressure and shows solubility of a gas in a liquid = pressure of gas above the liquid
S(gas) = k(H) P (gas)
S(gas) = solubility of the gas (usually in M
k(H) = Henry’s law constant
P(gas) = partial pressure of the gas
3 steps of chemical reactions
- bonds in reactants are broken
- atoms/ groups of atoms rearrange
- atoms form new bonds and combinations to make products
clues that a reaction has occurred
-absorption/release of energy
-color change
-production of a gas (bubbles)
-precipitates
precipitate
formation of a solid product from two solutions
purpose of chemical equations
shorthand ways of representing chemical reactions that use the chemical formulas of the reactants separated from the products by an arrow
also includes physical states of the reactants
reactant types
solid (s)
liquid (l)
gas (g)
aqueous (aq) meaning
substances dissolved in water
aqueous other names
dissolved in water
in solution
dilute
how is heat portrayed as a catalyst in a reaction
triangle over the arrow
catalyst
something used to speed up a reaction, not used up in it
chemical formula written over the arrow
law of conservation of mass
in any chemical reaction, the mass remains constant
mass of reactants = mass of products
coefficient uses in balancing equations
placed before the formula to support to law of conservation of mass
when balancing, never change:
subscripts in a chemical formula
why should we classify chemical reactions?
-predict products in a chemical reaction
-predict if a chemical reaction will occur
synthesis (combustion) reaction
two or more simple substances react, one complex product
-might require a small of heat/light energy
-forms binary/complex compounds
decomposition reaction
one complex substance reacts, two or more simple products
-opposite of a synthesis reaction
-most require a continuous supply of energy, used to break bonds in reactants
-reactions that absorb more energy to break bonds than released when forming are endothermic
-some form simple compounds instead of elements
single replacement reaction
an uncombined element and compound react, so the element displaces the same type of element in the compound, new element and compound produce
-to determine if this will occur, the uncombined reactant must be higher on the reactivity series than the similar element in the compound
double replacement reaction
two compounds react and exchange cations/anions, two new compounds produce
neutralization reaction
acid and base react, a salt and water produce
combustion reaction
hydrocarbon/carbohydrate and oxygen gas reacts, carbon dioxide and water produce
-heat/other energy also produced
-exothermic reaction
-water releases as vapor
activation energy
energy required to start a reaction
exothermic reaction
release of energy in the form of heat or light
when nonmetal oxides react with water
acid is produced
when metal oxides react with water
it forms a base
when metal oxides react with nonmetal oxides
ternary ionic compounds are produced
endothermic reaction
reactions that absorb more energy to break bonds than released when forming
precipitation reaction
two soluble ionic compounds in an aqueous solution exchange cations to produce two new ionic compounds
-at least one solid (precipitate) formed
neutralization reaction
reaction between an acid and a base to produce an ionic compound and water
-ionic compound composed of cation from base and anion from acid
-water formed from hydrogen ion from the acid and the hydroxide ion from the base
-some products are unstable and spontaneously dissolve and decompose to form a water and a gas
when an ionic compound dissolves in water, the resulting solution contains
the component ions
what happens when neither products are precipitates
no reaction
molecular equation
shows the complete neutral formulas for each compound in the aqueous reaction as if they existed as molecules
complete ionic equations
equations that describe the material’s structure when dissolved
spectator ions
ions that don’t participate in the reaction
net ionic equation
ionic equation where spectator ions are removed
Some laboratory procedures involving oxygen-sensitive reactants or products call for using water that has been boiled and then cooled. Why?
When the water is heated to boiling, oxygen becomes less soluble and will bubble out leaving the water oxygen-deficient
