Chapter 6, 7, 8 - Solutions, Acids, and Bases

Question 1

Solutions

Answer 1

solution = homogeneous mixture
homogeneous = uniform, same at any location within the mixture
mixture = more than/equal to 2 pure substances, variable proportions

Question 2

Solutes and Solvents

Answer 2

solute = substance of interest
solvent = median for solute
these definitions do not apply to aqueous solutions due to the presence of hydration spheres, water is always the solvent, everything else is the solute

Question 3

Aqueous solution properties

Answer 3

solutes can be electrolytes (when dissolved, causes solution to be electrically conductive) or non- electrolytes (when dissolved, does not alter conductivity of the solution)
hydrogen and hydroxide concentrations are changed by the solute

Question 4

Making solutions from pure solute

Answer 4

measure mass/number of moles of the solute based on the concentration and volume of ending solution
place solute into volumetric flask
fill the bulb half-way
swirl until everything is dissolved
fill up to the line using eyedrops at the end
pour into clean, dry erlenmeyer flask

Question 5

Reasons why some solutions cannot be made from pure solute

Answer 5

many are gases at room temperature
many are dangerous in pure form
many will absorb water or carbon dioxide from the atmosphere
many decompose rapidly in pure state

Question 6

Making solutions from concentrated solutions

Answer 6

the amount of concentrated solution to start with must be calculated
place concentrated solution into volumetric flask
fill the bulb half-way
swirl until everything is dissolved
fill up to the line using eyedrops at the end
pour into clean, dry erlenmeyer flask

Question 7

Solubility

Answer 7

solubility = how much solute can be dissolved into a given quantity of solution
equilibrium is reached when the rate of dissolving and recrystallization are equal
dissolution = collision between water molecules and solute particles
rate of dissolving = depends on collision force, frequency of collision (temperature)
recrystallization = solute particles re-attaching to the undissolved solute

Question 8

Types of substances (Arrhenius)

Answer 8

acid = hydrogen + electromagnetic non-metal, or an oxyacid anion, release hydrogen ions into aqueous solutions, turns litmus paper red
base = metal + hydroxide, release hydroxide ions into aqueous solutions, turns litmus paper blue
neutral = release neither hydrogen ion or hydroxide ion, or releases both hydrogen and hydroxide ions, litmus paper stay original colour or turns purple

Question 9

Types of solutions (Arrhenius)

Answer 9

acidic = pH of less than 7 at room temperature, sour, not slippery, hydrogen ion concentration is greater than hydroxide ion concentration
basic (alkaline) = pH of greater than 7 at room temperature, bitter, slippery, hydrogen ion concentration is less than hydroxide ion concentration
neutral = pH of 7 at room temperature, hydrogen ion concentration equal hydroxide ion concentration

Question 10

Problems with Arrhenius theory

Answer 10

only works in aqueous solutions
some bases are not hydroxides
some substances can act as acids or bases (amphoteric) depending on the reaction

Question 11

Bronsted-Lowry theory

Answer 11

acid = hydrogen ion donor in a chemical reaction, must have an ionizable hydrogen
base = hydrogen ion acceptor in a chemical reaction, must have a lone pair
acid/base reaction = transfer of a hydrogen ion
hydrogen ions do not actually exist in solutions, there are only hydronium ions

Question 12

Strong and weak acids

Answer 12

strong acid = ionizes completely in water to form aqueous hydrogen ions (100%), HCl, HBr, HI, HNO3, H2SO4
weak acid = ionizes only partially in water to form aqueous hydrogen ions (

Question 13

Strong and weak bases

Answer 13

strong base = ionic hydroxides that are highly conductive, have a very high pH and react quickly
weak base = usually molecular and polyatomic ions, have a low conductivity, a medium to high pH and react slowly

Question 14

Conjugate bases and acids

Answer 14

the conjugate of a weak acid will tend to act as a base in solution
the conjugate of a weak base will tend to act as an acid in solution
however, sometimes the conjugates will have little tendency to act as it is supposed to

Question 15

Determining an unknown concentration

Answer 15

measure pH using an indicator, ends up within 1 pH unit
indicator = weak acids in which the HA molecule has a different colour than the A ion, strength of the acid determines the point at which the colour change takes place (even mix of the two colours)
use a pH meter, which is permeable to hydrogen ion, ends up within 1/10 pH unit
titration uses stoichiometry to measure concentration

Question 16

Titration definitions

Answer 16

sample = solution of unknown concentration
titrant = a solution of precisely known concentration that can be reacted completely with the sample to determine the concentration of the sample
primary standard = a solution that can be made for a precisely known quantity of pure solute and used to determine the concentration of a titrant
end point = the volume titrant needed to produce the colour change in the indicator

Question 17

Criteria for titrations

Answer 17

we must know when the reaction is complete (both reactions are limiting), which happens at the equivalence point
phenolphthalein or any other indicator can be used to determine the endpoint
the concentration of the titrant must be precisely known
the reaction must be spontaneous
the reaction must be fast
no equilibrium should occur, therefore the sample or titrant must be strong

Question 18

Saturation

Answer 18

saturated = the concentration that is in equilibrium with undissolved solute
unsaturated = any concentration that is less than saturated
supersaturated = any concentration that is greater than saturated