test 1 chem 1302 dr. mcgrath Questions with 100% accurate solutions (A+ GRADED )

solutions; homogenous mixtures

the solvent dissolves the solute

since the solvent is the component present in greatest amount, it determines the .....?

phase of the solution

a concentrated solution contains...?

a lot of solute

a dilute solution contains ....?

little solute

enthalpy of solution (ΔHsoln) and IMFs

determine whether a solution can forum

1. when all forces are similar, ΔHsoln = ?

0; ideal solution (also: ΔVsoln = 0)

2. solute solvent interactions dominate;

ΔHsoln < 0: solution is non ideal and forms exothermically

3. solute- solute and solvent-solvent interactions dominate:

ΔHsoln > 0; solution is non ideal, and forms endothermically (if it forms)

4. solute- solute and solvent-solvent interactions are >>> solute-solvent interactions

ΔHsoln >> 0 and solution cant form

rule of thumb for predicting solubility

"like dissolves like"

for Ionic compounds in H20

ion dipole forces (+ end of h20 dipole attracts anions, - end of H20 dipole attracts cations) disrupt the solid --> hydrated ions in solution

dissolving too much solute

saturated solution

as a dynamic equilibrium is established

continuous dissolving and crystallizing, but apparently nothing happening (concentration of dissolved solid remains constant; quantity of undissolved solid remains constant)

solubility of gases (in H2O) decreased with increasing temperature, but (in all solvents) increase with increasing pressure

henrys law, solubility is proportional to pressure

Concentration

always defined as amount of solute / amount of solution ( or amount of solvent for molality)

molarity

moles solute (mol) / volume of solution (L)

% compositions

use part/whole x 100 with appropriate units ( mass, volume, etc...) ppm, ppb, ppt are simlilar to %: defined as part/whole x 10^6, 10^9, 10^12

molality

moles solute ( mol) / mass of solvent (kg), molality is temperature independent, so is useful when temperature varries

mole fraction

(mole of component)(total moles present), mole% = mole fraction x 100

mass %

100 g of solution

volume%

100 mL of solution

molarity (M)

1.00 L (i.e., 1000 mL) of solution

molality (m)

1.00 Kg (i.e., 1000g) of solvent

mole fraction (fancy x)

1 mole of (solute + solvent)

colligative propertires

depend on quantity (concentration0 of solute particles, not on their identity

Raoult's Law

adding a solute lowers vapor pressure ,compared to the vapor pressure of the pure solvent (remember to use fancy x solvent)

freezing point depression

boiling point elevation

osmosis

concentrated solution/dilute solution separated by semi permeable membrane; solvent passes from dilute ----. concentrated sides, flow continutes until osmotic pressure, PI, is reached

osmotic pressure PI

two solutions with same PI value are isotonic (isosmotic0

Solutions of electrolytes

electrolytes produce ions in solution, so # particles in solutions > formula unites dissolved...

equations for colligative properties must be modifies by vant Hoff factor

**** for raoults law, the equation is the same, but x must be calculated based on numbers of moles of all the particles in solution

remember that there are ions present

i @ infinite dilution

# of ions produced in solution per formula unit of solute. For more concentrated solutions, ion pair formation reduced the effective value of i

colloids are mixtures with particle size between that of solutions and suspensions, they wont settle out ...

they can be distinguished form true solutions by the Tyndall effect (light passing through colloid is scattered in all directions)

reaction rate

change in concentration per unit time (can refer to products or reactants)

- can be affected by concentration, temperature, surface area (particle size), catalysts/inhibitors

reaction rates are always > 0 (but remember, change in concentration of a substance being consumed is < 0)

true

use [A] to denote...

concentration of A

for a reaction forming compound

unites of reaction rate are always concentration/time (uslaly mol L-1 s-1 or M s-1)... also need to consider stoichiometry of the reaction (balanced equation); for the reaction aA ---> bB,

reaction rate =

measured rate

depends on the time span of the measurement

instantaneous rate

is the rate at one point in time

average time

all the instantaneous rates averaged over a period of time (usually whole reaction)

initial rate

= instantaneous rate at start of reaction

initial rate is usually the highest rate;

rates are usually higher at higher reactant concentrations

the rate law for a reaction is a relationship between reaction rate and reactant concentrations

for general aA + bB + ... -----> products, the rate law is