Solubility

Question 1

compare the dissociation between strong, weak, and nonelectrolytes

Answer 1

strong electrolytes completely dissociate (and therefore dissolve) in H2O weak electrolytes partially dissociate and fully dissolve in H2O i.e. weak acids and weak bases non electrolytes: don’t dissociate at all in H20, but do dissolve in H2O

Question 2

what is van’t Hoff factor?

Answer 2

refers to the # particles produced in solution per sole of substance

Question 3

What is the van’t Hoff factor of 1 mole of glucose?

Answer 3

1

Question 4

What is the van’t Hoff factor of 1 mole of NaCl

Answer 4

2: 1 NaCl = 1 Na+ and 1 Cl-

Question 5

What is the van’t Hoff factor of Ca(NO3)2?

Answer 5

3: Ca(NO3)2 = Ca++ and 2 NO3

Question 6

What is the van’t Hoff factor of HF?

Answer 6

between 1 and 2 This is because HF is a weak acid, it does not fully dissociate, and only partially dissociate.

Question 7

What is the process of dissolution of electrolytes in H2O (3 steps)

Answer 7

agitation: i.e. stirring; an endothermic process because you’re adding energy to the system dissociation: the ions are pulled away from one another; an endothermic process because you’re breaking bonds, which requires energy solvation: the ions form bonds with water; an exothermic process d/t bond formation expels energy

Question 8

How is the process of solvation of electrolytes differ between polar-nonelectrolytes and nonpolar-nonelectrolytes?

Answer 8

electrolytes undergo agitation, dissociation, and solvation polar-nonelectrolytes only undergo agitation and solvation. They do not undergo dissolution because the molecule doesn’t separate nonpolar-nonelectrolytes can only undergo agitation, but cannot undergo dissolution or solvation, as they cannot dissolve in H2O

Question 9

Distinguish between an unsaturated, saturated, and supersaturated solution

Answer 9

unsaturated: the concentration of solute is less than the solubility factor and thus if more solute can be added and dissolved into the solution saturation: concentration of solute - colubility factor. no additional solute will dissolve if added. supersaturated solution: concentration of solute is greater than the solubility factor. If more solute is added, it will cause precipitation

Question 10

How is solubility affected by Temp and P?

Answer 10

-directly proportional to temp when dissolving solids and liquids into other liquids/aqueous solutions -inversely proportional to temp when dissolving gases into liquids (colder temps make pop more fizzy) -solubility has no relation to P when dissolving solids and liquids into other liquids/aqueous solutions; hence pressure doesn’t affect solubility factor -solubility is directly proportional to pressure when dissolving gases. If you increase pressure, it will encourage that gas to dissolve into the liquid

Question 11

What electrolytes are always soluble in H20?

Answer 11

Group 1 ions (i.e. Na+, K+), H+, NH4+ NO3-, CH3COO- (acetic acid), and ClO4- Note not all elements that have a +1 or -1 charge will completely be soluble in H2O, but all electrolytes that are completely soluble in H2O have a +1 or -1 charge

Question 12

What electrolytes are usually soluble in H2O?

Answer 12

Ag⁺, Pb²⁺, Pb⁴⁺, Hg₂²⁺, Hg²⁺

CO₃^2-, PO₄^2-, S^2-

Question 13

If one mole of reactant makes 1 mol of product, and the experiment yield is 75%, how many moles of product will you get from 1 mol of reactant?

Answer 13

1 mol reactant = ( 1 mol product/ 1 mol reactant ) x 75% = 0.75 mol

Question 14

under standard conditions, pure elements in their natural phase will have a H_f ____ and a G_f____?

Answer 14

H_f and G_f will be zero

Question 15

True or False: cooling any substance to 0K will decrease entropy of that substance to 0?

Answer 15

False. Only entropy of a simple, chemically pure element will have 0 entropy at 0K

Question 16

2H₂ (g) + O₂ (g) → 2H₂O (g)

If G_f of H₂O = -288. What is ∆G_rxn at standard conditions?

Answer 16

G_f of H₂ and O₂ are zero at standard conditions

∆G_rxn = Σn·products - Σn·reactants = (-288 x 2) - 0 ≈ -290 x 2 = 580

Question 17

What is the natural phase of bromine at standard conditions?

Answer 17

liquid

Question 18

In a rxn, Bromine gas is reacted with another reactant under standard conditions. Is the G_f bromine = 0?

Answer 18

No, because bromine is not in its standard state, as it’s standard state is liquid, not gas

Question 19

What is the oxidation state of any pure element?

Answer 19

0

Question 20

What is usually the oxidation state of an ion?

Answer 20

usually is the same number as the charge it has

i.e. Zn²⁺ has oxidation state of 2

Fe³⁺ has oxidation state of 3

Question 21

What is the oxidation state of the following molecules?

1) Hg₂²⁺
2) O₂
3) O
4) F₂
5) F
6) H when bonded to a metal
7) H when bonded to a nonmetal

Answer 21

1) each Hg has an oxidation state of +1
2) oxidation state = 0 because its in its natural state
3) -2
4) 0 (because its in its natural state)
5) -1
6) -1
7) +1

Question 22

What is the preferred oxidation state of N?

Answer 22

-3

Question 23

What is the oxidation state of each of the molecules in the following compounds:

1) MgCl₂
2) V₂O₅
3) SO₄^-2

Answer 23

1) Mg = +2, Cl = -1
2) V = +5, O = -2
3) SO₄^-2: S + O = -2 ⇒ S + 4(-2) = -2 ⇒ S - 8 = -2 ⇒ S = +6

Question 24

What is a ligand?

Answer 24

a molecule that attaches themselves to ions with high + charge density; bonds between the ligand and + charge molecule (usually a transition metal) will create a coordinate covalent bond (neither an ionic or covalent bond).

i.e. H2O, CN-, NH2, OH-

Question 25

What type of reaction takes place with a ligand and + charge molecule? (aka what type of reaction makes a coordinate covalent bond?)

Answer 25

A Lewis Acid-Lewis Base rxn, as the ligand acts as the e- donor and the cation acts as the e- acceptor

Question 26

Which has a bigger radius, N or F?

Answer 26

N because atomic radius decreases going from L to R across a period of the periodic table

Question 27

What is the trend of electron affinity across the periodic table?

Answer 27

EA (or the energy released when an e- is added) increases going from L to R and bottom to top across the periodic table. Thus, F has the highest negative EA value and releases the most amount of energy when an e- is added to it.

Question 28

The more negative an EA value is, the more ____(unstable or stable) that atom will be when you add an e-

Answer 28

stable

Question 29

a smaller atomic radius will ____ (decrease or increase) the negative value of EA

Answer 29

increase (because the higher the negative EA value, the more energy that is released from the molecule when an e- is added; hence the more exothermic the rxn is when adding an e-)

Question 30

What is effusion?

Answer 30

refers to the ability of a gas to travel through a small opening

Question 31

Out of solids, liquids, aqueous solutions, and gases, which are included in the equillibrium constant equation?

Answer 31

only aqueous solutions and gases. solids and liquids are not included into the equation

Question 32

Equation for Equillibrium constant

Answer 32

K_c = products / reactants = [C]^c[D]^d / [A]^a[B]^b

Generic equation = aA + bB → cC + dD

Question 33

What does each of the following mean:

1) K_c > 1
2) K_c = 1
3) K_c < 1

Answer 33

1) K_c > 1 Products are favored (aka the forward rxn is favored)
2) K_c = 1 Products and reactants are equally favored
3) K_c < 1 Reactants are favored (aka the reverse rxn is favored)

Question 34

What does each of the following mean:

1) Q > K
2) Q = K
3) Q < K

Answer 34

1) Q > K There are excess products; thus there will be a shift to the L to create more reactants (aka reverse rxn is favored to reach equillibrium)
2) Q = K reactants and products are in equillibrium
3) Q < K there are excess reactants; thus there will be a shift to the R to create more product (aka forward rxn is favored to get to equillibrium)

Question 35

How does K relate to ∆G?

Answer 35

K > 1 will give a - sign for ∆G, which makes sense because when products are favored, the rxn must be exothermic and spontaneous, and in an exothermic/spontaneous rxn ∆G is -

K < 1 will give a + sign for ∆G (forward rxn is endothermic and nonspontaeous)

Question 36

Consider the following rxn, which is at equillibrium: C (s) + H₂O (g) ⇔ CO (g) + H₂ (g)

How is the equillibrium (constant) affected in each of the following situations:

1) H₂O is added
2) C is added
3) a catalyst is added
4) increasing the P_total by decreasing the V

Answer 36

1) there will be a shift to the R to create more product
2) there will be no shift because C is a solid and solids are not counted in equillibrium equations
3) a catalyst will not alter the equillibrium constant; it can only affect the rate of the rxn and thus make a reaction that is not at equillibrium reach equillibrium faster
4) this will shift the rxn towards the side that has the least amount of moles; in this case this would be towards the L, as there is 1 mole of H2O and a total of 2 moles of products

Question 37

How does increasing or decreasing Volume affect the equillibrium of a reaction?

Answer 37

Altering the volume will have an effect if there is an imbalance of moles on each side of the equation (again, not counting the moles making up the solid or liquid, only the aqueous or gas)

If P_total increases d/t a decrease in V, then there will be a shift toward the side with the least amount of moles

If P_total is decreased d/t an increase in V, there will be a shift toward the side with the more amount of moles

Question 38

How can you adjust the P and V of an equillibrium equation?

Answer 38

you adjust by addition of an inert gas in a flexible container (i.e. a cylinder with a moving piston)

Question 39

Effect of temperature on equillibrium:

1) for an endothermic rxn, heat is treated as a ____
2) for an exothermic rxn, heat is treated as a _____

Answer 39

1) reactant
2) product

Question 40

For an endothermic rxn, if you add heat to the rxn, there will be a shift towards the ____ and the K will ____

Answer 40

shift towards the right

K will increase

Question 41

For an exothermic rxn, if you add heat, there will be a shift towards the ____ and K will ____

Answer 41

shift towards the L (reactants are favored)

K will decrease

Question 42

What factor is the only factor that affects the value of the equillibrium constant?

Answer 42

temperature will only change the equillibrium constant value

adding reactants or products, and adjusting P and V will shift the rxn, but the equillibrium constant itself is unchanged

Question 43

How is equillibrium r/t rate constants?

Answer 43

R_forward = k_f[A] aka the rate of the forward rxn is equal to the rate constant of the forward rxn times the concentration of the reactant

R_reverse = k_r[B] aka the rate of the reverse rxn is equal to the rate constant of the reverse rxn times the concentration of product

At equillibrium: k_f[A] = k_r[B] ⇒ k_f/k_r = [B]/[A] aka products over reactants

K_eq = k_f/k_r aka the equillibrium constant is equal to the ratio of the forward rxn and reverse rxn rate constants

Question 44

Reversing an equillibrium equation ____ the equillibrium constant

Answer 44

inverts

aka it is the reciprocal of the equillibrium constant

Question 45

Fomration Equillibria: combining multiple equillibria results in the ____ of the equillibrium constants

Answer 45

multiplication

i.e. Cu²⁺ (aq) + 4NH₃ (aq) ⇔ Cu(NH₃)₄²⁺ K₁ = 1x10¹³

Cd²⁺ (aq) + 4NH₃ (aq) ⇔ Cd(NH₃)₄²⁺ K₂ = 1x10¹²

Cd(NH₃)₄²⁺ + Cu²⁺ ⇔ Cu(NH₃)₄²⁺ + Cd²⁺

K₂ must be the reciprocal because the equation must be reversed to give the last equation

K_{1 and 2} = K₁ (1/K₂) = 10¹³/10¹² = 10¹

Question 46

As K_sp increases, molar solubility _____

Answer 46

increases

Question 47

Indicate in each of the following situations if a precipitate will form:

1) Q_sp > K_sp
2) Q_sp = K_sp
3) Q_sp < K_sp

Answer 47

1) Q_sp > K_sp Reverse rxn is favored bcz there are excess products; thus there will be a shift to the L and precipitate will form bcz you’ll be making more reactant. Represents a supersaturated solution
2) Q_sp = K_sp you are at equillibrium; thus no more solute can dissolve and no precipitate is formed. Represents a saturated solution
3) Q_sp < K_sp you have excess reactants; there will be a shift to the R, more solute is dissolving and thus no precipitate is formed. represents an unsaturated solution

Question 48

Equation to find Q

Answer 48

Q = products/reactants

same as K, but you are using initial concentration values instead of at equillibrium values

Question 49

What is the common ion effect?

Answer 49

a salt’s solubility will decrease if it is added to a solution containing a common ion

a salt’s solubility will increase if it’s added to a solution containing something that removes a common ion (adding the salt to an solution with acid)

Question 50

What is a dissociation constant indicate?

Answer 50

it tells you how difficult it is to separate a complex

For the rxn AB ⇔ A + B, K_d = [A][B] / [AB] = k₂/k₁

k₂ = forward rate constant k₁ = reverse rate constant

The larger the forward rate constant, the larger the value of K_d

The larger the value of K_d, the less difficult it is to separate the complex; in other words, the less affinity substrate A has for substrate B

Question 51

What is the affinity constant?

Answer 51

K_aff tells you the strength of binding of molecule to ligand

For rxn A + B ⇔ AB, the Affinity constant is K_aff = [AB] / [A][B] = k₁/k₂

Notice this is the inverse/reciprocal of the dissociation constant: K_aff = K_d

A smaller K_aff indicates a smaller affinity for the AB complex; aka the less affinity A will be attached to B