deck

Question 1

when Kc > 1, is the reaction efficient or inefficient?

Answer 1

efficient

Question 2

what is happening in a solution with both solid and liquid in it at equilibrium?

Answer 2

ions in the liquid are solidifying (precipitating) at the same rate that the solid is dissolving

Question 3

on a concenttration/time graph, what does the slope represent?

Answer 3

rate of change

Question 4

what does Kc tell us?

Answer 4

called the equilibrium concentration constant

tells us how well a reaction proceeds, dependant on reactant concentration and coefficients in equation (more particles = faster rate, larger coefficient = greater effect on rate)

Kc (and K) are different for every reaction

rate varies as [reactants]^(any coefficients)

Question 5

what is the Kc expression

Answer 5

([C]^c x [D]^d) / ([A]^a x [B]^b)
where C and D are products, A and B are reactants, and the lowercase letters are any coefficients

Question 6

what is happening in regards to

• amount of reactants/products
• Kc expression
• which side is favoured
• efficiency

when Kc<1?

Answer 6

large amount of reactants, small amount of products
bigger denominator in Kc expression
reactants are favoured
reaction proceeds less than 50%
inefficient reaction

Question 7

rules for substances included in Kc expression for
H2O
solids
liquids

Answer 7

• include H2O(g)
• in aqueous system, don’t include H2O(l) ([water] = 1)
• don’t include solids (concentration cannot vary)
• in gaseous system, don’t include liquids

Question 8

what is the rule saying that when a stress is applied to an equilibrium system, the system response is the opposite to minimize the stress?

Answer 8

le chatelier’s principle

Question 9

true or false, we can determine which side is favoured using equilibrium shift

Answer 9

false, only from Kc value

Question 10

which direction does equilibrium shift when we add products?

Answer 10

left, towards reactants

Question 11

what is the system response to adding reactants

Answer 11

concentration of reactants decreases, concentration of products increases

Question 12

how does system response effect equilibrium

Answer 12

equilibrium shifts towards the side that increased from the system response (THE OPPOSITE SIDE THE STRESS WAS ADDED if the stress was adding reactants of products)

Question 13

true or false, you cannot change pressure in liquid equilibria

Answer 13

true, only gas equilibria

Question 14

name the 3 ways you can change pressure in a gaseous system

Answer 14

add/remove a reactant/product - equilibrium shifts away from the side that was added to or towards the side from which was removed

reduce volume of container - equilibrium shift towards the side with fewer gaseous moles (opposite for an increase in volume), if the same then no effect

add an inert gas - no equilibrium shift

Question 15

true or false, reducing container volume in an equilibrium system shifts equilibrium towards the side with more gaseous moles

Answer 15

false, shifts towards the side with less gaseous moles

Question 16

true or false, increasing container volume in an equlibrium system shifts equilibrium towards the side with more gaseous moles

Answer 16

true

Question 17

what can affect the value of Kc and why

Answer 17

only temperature. it is like adding a stress, the energy term will be a reactant or product

add=equilibrium shifts away
remove=towards

Question 18

when Kc increases as temperature increases, which way does equilibrium shift?

Answer 18

right (towards products)

Question 19

when Kc increases as temperatire increases, is the reaction endothermic or exothermic?

Answer 19

endothermic

Question 20

bronsted lowry definition of acid

Answer 20

can donate H+ ions
reacts with water to form H3O+ (hydronium ion) and a conjugate base

Question 21

bronsted lowry definition of base

Answer 21

can accept protons (like H+), meaning it has a negative charge
reacts with water to produce OH- (hydroxide ion) and a conjugate acid

Question 22

what is [H+] in a strong acid solution and why

Answer 22

[H+] = [strong acid]
(original concentration of the strong acid)

because it’s 100% ionized

Question 23

assumption for strong acids reacting with water at equilibrium (amount of reactant and product)

Answer 23

very little reactant (~0%), lots of products (~100% each)

Question 24

assumption for weak acids reacting with water at equilibrium (amount of reactant and product)

Answer 24

lots of reactant (~99%), very little products (~1% each)

Question 25

when do you use the forward arrow

Answer 25

reactions with strong acids/bases and water to show that they fully ionize/dissociate

Question 26

efficiency of strong and weak acid reactions relative to Kc

Answer 26

strong - efficient, Ka>1 weak - inefficient, Ka<1

Question 27

what is Ka, Kb

Answer 27

Ka is Kc but for acids Kb is for bases they are inversely related

Question 28

what is the net ionic equation for HCl(aq) + NaOH(aq) <=> H2O(l) + NaCl(aq) CHEM 30 NET IONIC

Answer 28

H3O+(aq) + OH-(aq) <=> H2O(l) + H2O(l) 2H2O(l) as the product is incorrect

Question 29

what is a polyprotic acid/base

Answer 29

polyprotic acids can donate more than one H+ to a base (they have more than one acidic H that is not bonded to a C) polyprotic bases can accept more than one H+ from an acid (they have a charge that is more negative than 1-) reactions with these happen one proton transfer at a time (multiple reactions)

Question 30

what is an amphiprotic species/substance and what is the most common one?

Answer 30

they can act as both a base and an acid in different reactions water is the most common conjugate acids of a polyprotic base OR conjugate bases of a polyprotic acid found on both sides of the acid/base table

Question 31

how are strong acids communicated in net ionic equations?

Answer 31

H3O+ because they ionize completely

Question 32

how are weak acids communicated in net ionic equations?

Answer 32

as they are because they don't create much H3O+ at all

Question 33

how are strong bases communicated in net ionic equations?

Answer 33

OH- because they dissociate completely

Question 34

how are weak bases communicated in net ionic equations?

Answer 34

as their anion because they dissolve but don't make much OH- at all (ex. NaNO2 would be NO2- in net ionic)

Question 35

when two amphiprotic species are the reactants in an equation, how do you tell which one donates a H+?

Answer 35

the one that is the stronger acid on the acid/base table acts as the acid and donates the H+ to the other

Question 36

how to calculate Kb from acid/base table

Answer 36

Kb = (1.0x10^-14) / (Ka)

Question 37

how to know if a reaction with H3O+ or OH- ions proceeds and which side is favoured

Answer 37

always proceeds with any hydronium or hydroxide ions, the side opposite from these ions is favoured

Question 38

how to calculate pH given [OH-]

Answer 38

pH = 14.00 - (-log[OH-])

Question 39

what is the shortcut to solve for [H3O+] in a weak acid

Answer 39

[H3O+] = square root of ([WA] x Ka) ASSUMING [H3O+] << [WA] (<< means significantly less than)

Question 40

what is the shortcut to solve for [OH-] in a weak base?

Answer 40

[OH-] = square root of ([WB] x Kb) ASSUMING [OH-] << [WB] (<< means significantly less than)

Question 41

true or false, pH is an equilibrium concentration

Answer 41

true

Question 42

describe the basic steps and formulas to solve this question the volume of 6.00mol/L NaOH required to neutralize 2.20kg of HN3(l) is ________L.

Answer 42

convert kg to g, find molar mass of HN3, and use n=m/M. using molar ration (1:1) obtain n for NaOH, use V=n/c to solve. (answer = 8.52L)

Question 43

what is the Ka expression for hydroazoic acid (HN3, H3O+, H2O, and N3- are involved in the reaction)

Answer 43

Ka = ([H3O+][N3-]) / [HN3]

Question 44

describe the basic steps and formulas to solve this question there is a .15mol/L concentration of NH3(aq). it's pH is _____

Answer 44

[WB] = .15mol/L find Ka of conjugate acid and use Kb = Kw / Ka. find [OH-] using square root of ([WB] x Kb). find pOH by taking the -log of that answer. find the pH by subtracting 14.00 - that answer. (answer: 11.21)

Question 45

i hope you know what indicators are

Answer 45

.

Question 46

basic reactant and product names for a titration

Answer 46

acid + base <=> salt + water

Question 47

generalizations of the types of acid/base used in sample and titrant consider acid/base strength, measured concentration (known or unknown), and where the indicator is

Answer 47

sample - generally weak acid/base, unknown concentration, with a pH indicator titrant - generally strong acid/base, known concentration

Question 48

what reaction is happening in a weak acid titration when 0mL if titrant is added

Answer 48

WA + water <=> hydronium ion + CB ex. HCN + H2O <=> H3O+ + CN

Question 49

where is the starting pH of a weak acid titration and why?

Answer 49

generally between 2 and 6 (never 1 or 7) because a small amount of H3O+ has already formed in reaction with water, but there is not much product in a reaction with a weak acid so it will be higher than 1

Question 50

what reaction is happening during a monoprotic weak acid titration?

Answer 50

WA + hydroxide ion <=> water + CB ex. HCN + OH- <=> H2O + CN-

Question 51

where is the buffer region in a monoprotic weak acid titration and what is present there?

Answer 51

the most flat section of the graph between the starting point and the equivalence point. 1/2 of the sample is the WA, the other 1/2 is its CB

Question 52

true or false, signifying to us the end of the reaction, the equivalence point has some excess titrant

Answer 52

false, there is no excess titrant at the equivalence point, only after

Question 53

what is the equation to the equivalence point in a monoprotic weak acid titration

Answer 53

WA + OH- <=> H2O + CB same equation as what is happening during the titration

Question 54

how to determine the overall equation for a polyprotic weak acid / weak base titration

Answer 54

add all equivalence point equations (add all reactants on one side, add all products to the other, combining coefficients if needed, likely for water and hydronium/hydroxide)

Question 55

what can be a buffer

Answer 55

must be a WEAK ACID AND ITS CONJUGATE BASE

Question 56

true or false, HCl and Cl- is a buffer

Answer 56

false, its a strong acid not a weak acid (must be weak acid)

Question 57

true or false, H3PO4 and PO4 3- is a buffer

Answer 57

false, not conjugates (must be conjugates)

Question 58

how to determin e the pH at which a buffer is efective

Answer 58

take Ka of the weak acid form of the buffer, use pH = -log(Ka) to find pH

Question 59

what is the general equation when solving buffer pH range?

Answer 59

react WA + water <=> CB + H3O+

Question 60

true or false, water cannot be a buffer with hydroxide ion

Answer 60

true, water does not act as an acid generally