4. Chemical Reactivity Flashcards by J Y

what does pressure favor for equilibrium

Favours form of fewer moles of gas

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what is the equilibrium constant

conc of reactant and product at equilibrium

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what is the unit for equilibrium constant

molL-1

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what does a large kc >10^5 mean

completely convert reactant to product

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what does a very small kc <10^-5 mean

very small number of reactants turn into products

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what is the unit for solubility

gL-1

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what is the reaction quotient

determines direction reaction shifts to reach equilibrium

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what does it mean if Q<K for the reaction quotient

forwards/to the right

reactant to product

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what does it mean if Q>K for the reaction quotient

reverse/to left

products to reactants

precipitation

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what does it mean if Q=K for the reaction quotient

reaction is already at equilibrium

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what is Q regarding the reaciton quotient

ionic product

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what does increased conc of the ion or common ion effect do to the reaction in terms of direction itll proceed and solubility

drives reverse reaction

decrease solubility

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what is the common ion effect

add reagent with which cations form soluble complex

eg Ag+ + 2NH3 -> [Ag(NH3)2]+

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what is the colour of phenolphthalein in acid and base

acid = colourless
base = pink

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what is the colour of bromothymol blue in acid and base

acid = yellow
base = blue

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what does acids do in terms of protons

transfer/donate H+ to others

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what does bases do in terms of protons

accept H+ from others

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increase conjugate acid strength does what to the base strength

decreases conjugate base strength and vice versa

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what is ka’s relationship with acid strength

increased ka = stronger acid

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what is ka’s relationship with pka

increase ka = decrease pka

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what is pka’s relationship with acid strength

small pka = stronger acid

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what is the equation relating pka and ka

pka = -log10ka

ka = 10^-pka

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if the buffer is equimolar then what is the relationship of the pH of the buffer and the pka of acid

pH buffer = pka acid

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for a titration of weak acid/base and added strong acid/base how do you calculate the pH of the original acid

added volume of strong base/acid = 0 at this point

write reaction equation for the weak acid/base
write ka expression
solve for [H3O+]

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for a titration of weak acid/base and added strong acid/base how do you calculate the volume of added acid/base at equivalence

equivalence point = n(acid) = n(base) 1. find n(weak acid/base) 2. mole ratio of weak acid/base and added volume 3. find n(added volume) from ratio mole 4. find volume thats added via C=n/V

for a titration of weak acid/base and added strong acid/base how do you calculate the volume of added acid/base when pH = pka

pka = pH when v(added volume) = 1/2 amount of weak acid/base v(added) = v(equivalence)/2

for a titration of weak acid/base and added strong acid/base how do you calculate pH

1. write equation for reaction between weak acid/base with added strong acid/base 2. identify ka or kb expression 3. find [ion react with H2O] via C=n/V 4. solve ka or kb for [H3O+]

for a titration of weak acid/base and added strong acid/base how do you calculate the pH after x amount of added volume is added

after equivalence will have extra of added volume 1. new conc = original conc x (extra volume/total volume) 2. find [H+] to find pH

what is the buffer zone

where buffer is effective over pH range of pka +/- 1

for a zero order reaction what is the change in rate when there is a change in [A] what equation represents this - rate is proportional to.. and rate = ...

no change in change in rate rate proportional to [A]^0 rate = k

for a first order reaction what is the change in rate when there is a change in [A] what equation represents this - rate is proportional to.. and rate = ...

rate x2 when [A] x 2 rate proportional to [A]^1 rate = k[A[

for a second order reaction what is the change in rate when there is a change in [A] what equation represents this - rate is proportional to.. and rate = ...

4 x rate when [A] x 2 rate proportional to [A]^2 rate = k[A]^2

for a zero order reaction what is the unit of k

molL^-1s^-1

for a first order reaction what is the unit of k

s^-1

for a second order reaction what is the unit of k

Lmol^-1s^-1

for a third order reaction what is the unit of k

L^2mol^-2s^-1

what is the [R] rate law equation for first order reaction

[R] = [Ro]e^(-kt) ln[R] = ln[Ro] - kt

for a first order reaction what is the plot of ln[R] vs time like

linear

what are the 2 possible combinations of 2nd order reaction

single reactant in 2nd order or 2 reactants in first order

what assumption is made for a second order reaction that is made up of 2 1st order reactions

that one of the reactants's conc is very large

what is the rate law equation for second order reaction and a pseudo first order

1/[R] = 1/[Ro] + kt k1 = [R] pseudo first order

what is the half life rate equation for zero order reactions

[R] = [Ro] - kt t1/2 = [Ro]/2k

what is the half life rate equation for first order reactions

ln[R] = ln[Ro] - kt t1/2 = ln2/k

what is the half life rate equation for second order reactions

1/[R] = 1/[Ro] + kt t1/2 = 1/[Ro]k

what is the half life

time for conc of reactant to fall to 1/2 its original value

what are the 2 conditions for a effective collision

molecule has high enough energy to overcome activation energy correctly aligned molecules

what is the relative energy of the multistep reactivity when it comes to reactive intermediates

minimum energy

what is the relative energy of the multistep reactivity when it comes to transition states

max energy

when do catalysts act in the reaction pathway

usually early step and regenerates in later step

what are homogenous catalysts

catalysts working in same phase as reaction

what are heterogenous catalysts

catalysts working in different phase from reaction

what do catalysts do - 2 possible actions

provides different path of lower Ea = faster reaction rate or molecules are aligned by the catalyst

what is the rate determining step

the slowest step

what are bronstead acids

proton H+ can be taken by base

what are bronstead bases

take proton H+ from acid

what are amphoteric substances

can act as both acid or base

what does a -pH mean

pH is + for [H+] <1molL^-1 -pH means very acidic

what are the bonds like in strong acids what does this mean for the distance between atoms and the e- density

short bonds so atoms are closer together e- density between 2 atoms is large

decrease in e- density of bond means what for the strength of the bond

decrease strength of bond

what are the 2 ways that the e- density in bond regarding acidity of substance be affected

decrease amount of charge charge stabilization

why does decreasing the amount of charge affect the e- density in bond regarding acidity of substance

easier for + molecule to lose + H+ ion so if acid loses H+ then the conj base is 1 unit charge more negative

what are the 2 ways that charge stabilization affect the e- density in bond regarding acidity of substance

1. inductive effects 2. delocalisation

for charge stabilization affecting the e- density in bond regarding acidity of substance - explain the inductive effects

presence of nearby electronegative atom/e- withdrawing groups move charge away from acidic H = weaker H bond

for charge stabilization affecting the e- density in bond regarding acidity of substance - explain the delocalisation effects

spread charge over larger number of atoms - occurs via resonance

regarding speciation if pH < pka what does this mean for the acid and base forms

have higher acid forms (HA) than base form proportionally

regarding speciation if pH > pka what does this mean for the acid and base forms

have higher base forms (A-) than acid form proportionally

how do you calculate the pH of an amphoteric substance solution

pH = 1/2(pka1 + pka2)

buffers work best in what range

at pH = pka +/- 1

4. Chemical Reactivity Flashcards

(68 cards)