5.1.1 Flashcards
In Arrheinus’s equation what effect does Ea have on the rate constant?
higher Ea
lower K value
What effect does temperature have on the rate constant in Arrheinus’s equation?
higher temp
larger K value
What condition is Kc dependent?
temp
If the backwards temperature is endothermic, what happens to Kc when temp inc?
Kc dec
What happens to KC when temperature dec if the backwards reaction is endothermic?
Kc inc
What state symbol is allowed in the Kc equation?
aq
2NO + O2 = 2NO2
What effect does a decreased pressure have?
lower conc of everything
denominator dec more than top so system no longer in eq
eq shifts to left
NO2 dissociates more to restore Kc
conc of reactants inc and products dec
until eq is restored
N2O4 = 2NO2
What effect does pressure have?
inc in pressure inc conc of everything
numerator in Kc exp inc more than denominator and system no longer in eq
eq shifts to left
NO2 dissociates more to restore Kc
reactants inc products dec
H2 + I2 = 2HI
What effect does temperature have?
inc in pressure inc conc of everything
both terms in Kc affected
Kc not changed so eq doesnt shift
eq stays the same
What are acids?
proton donors
What are bases?
proton acceptors
What is the different dissociations in strong acids and weak acids?
strong acids fully dissociate
weak acids partially dissociate
What is acid strength determined by?
H+ conc
What is the difference between dissociations in strong and weak bases?
strong base fully dissociates
high OH- conc
weak base partially dissociates
low OH - conc
The larger the value of Ka?
the greater the dissociation
What is a buffer solution?
resists changes in pH when small amounts of acid / alkali are added
What do acidic buffers do?
maintain pH lower than 7
What do basic buffers do?
maintain pH higher than 7
How do you make an acidic buffer?
weak acid and it’s salt conjugate base
How do you make a basic buffer?
weak base and its salt conjugate acid
What happens when you add acid to a buffer?
CH3COOH = CH3COO- +H+
H+ react with CH3COO- and equilibrium shifts left
What happens when you add acid to a buffer?
CH3COOH = CH3COO- +H+
lowers H+ concentration so CH3COOH dissociates to replace them
equilibrium shifts to the right
Where is the equivalence point?
centre of the verticla section
What is the equivalence point?
equivalent number of moles of each chemical required by the mole ratio in the equation
What happens in the initial section of a strong acid- strong base graph?
acid is in large excess
addition of 1/2cm3 of NaOH doesnt change the pH that much
How do you find the pH at equivalence?
centre of vertical section is pH
Where will the vertical line be on a strong acid strong base graph?
25cm3
What does the final section of a strong acid - strong base graph look like?
levels off at max pH
Why is the pH at equivalence 7 for a strong acid - strong base graph?
neutral substances formed
Why would the pH at equivalence be below 7 for strong acid weak base likee ammonia and hcl?
Ammonium chloride dissociates into ammonium ions and chloride ios
Ammonium ions donate a proton making the pH slightly acidic
Why is the pH at equivalence for weak acid strong base higher than 7?
the CH3COO- ions accept H+ from water to form ethanoic acid
so it acts as a base
Where will the graph for weak acid weak base start?
pH 3
Where will the graph for weak acid weak base end?
pH 10
Why is the pH at equivalence 7 for weak acid weak base? ethanoic acid and ammonium hydroxide
ethanoate ion = weak base
ammonium ion = weak acid
weak bases accept a H+ and weak acids donate a proton so they cancel eachover out
so pH is 7
What section must indicators fall in?
VERTICAL REGION
What does a lower pKa mean?
stronger acid
What is the only condition to affect K?
temp
The larger K
the higher the rate of the reaction
The higher the Kc?
the futher the equilibrium lies to the right
What is the only factor to affect Kc?
temp
The higher the Kp<
the futher the equilibrium lies to the right
What does a higher Ka value mean?
more dissociated the weak acid is
What is the only condition to affect rate constant?
temp
What does a larger K value mean?
higher rate
What happens to balancing numbers in the Kc?
become powers
What does a higher Kc indicate?
equilibrium lies fither to the rightWhat
What is the only condition to affect Kc?
temop
What does c represent in Kc?
equilibrium concentrations
Whatmethod is sued to calc concentrations in Kc?
ICE
What does a higher Kp indicate?
eq lies futher to the right
What is the only condition to affect Kp?
temp
what does p represent in Kp?
partial pressures of gas components
What is thr equation for partial pressure?
mole fraction
X
total pressure
What is Ka used to calculate?
pH of weak monobasic acids
What does a higher Ka indicate?
more dissociated the weak acid
What does a lower pKa indicate?
more weak acid is dissociated
What is the ionic product of water used to calculate?
pH of strong alkalis where we know [OH-]
