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161 Cards in this Set

  • Front
  • Back

What is reaction rate?

Change in concentration of reactants/products with unit time

How do we find reaction rate at a particular instant?

Draw a tangent and calculate gradient of graph where y-axis is concentration and x-axis is time

What are the units of reaction time?


What does a rate expression tell us?

How certain species affect the rate of reaction.

Activation energy

Minimum energy required to break bonds so that a reaction can occur


changes the rate of reaction by providing an alternative pathway to lower the activation energy without being chemically altered itself.

What is the 1st order of reaction and what does it mean?

Species in rate expression is raised to the power of one. If the concentration of this species doubles so will the rate of reaction

What does the graph look like for a 1st order reaction?

Directly proportional linear line through the origin

How do you say?:

rate = [A]^1[B]^2

1st order reaction with respect to A

2nd order reaction with respect to B

Overall, it is a 3rd order reaction

What does a graph for a zero order reaction look like?

completely horizontal - any change in the species has no affect on the rate of reaction

what do square brackets represent?


What is the only way of finding out the order of reactions?


Keeping all but one reagent species the same at a constant temperature and measuring the effect on rate this has.

What is the rate determining step?

The slowest stage in a reaction

The overall rate of a multi-step process is governed by the slowest step

What is the rate constant?


What is the only factor that affects the rate constant?


What kind of order of reaction can be left out of the rate equation?

Zero order - since anything raised to the power of 0 is 1.

How can we find the initial rate of reaction and why would we?

Draw tangent and calculate gradient when time = 0. Initial rate of reaction is the steepest.

How do we know whether a reactant is involved in the rate determining step?

Species is present in the rate equation

What does the order of a reaction tell us in terms of the rate determining step?

The number of molecules involved of that reagent in the rate determining step

What order is a reaction if it is straight on rate/(conc^2) graph?

2nd order

Why may catalysts appear in the rate equation but NEVER appear in the stochiometric equation?

The catalyst affects the rate of reaction but is chemically unchanged

Why does a catalyst speed up the rate of a reaction?

Provides an alternative pathway, lowering the activation energy meaning that a higher proportion of particles have the required energy to collide more often and thus successfully react.

What is a heterogeneous catalyst?

Catalyst is in a different phase to the reactants

Why do we use a rate constant?

Allows us to get rid of the "proportional to" sign and use an equals sign instead

How do we work out the overall rate of reaction?

Add up the orders of reaction

What are the units of the rate constant?

Varies depending on the order of reactions for the species involved

What is dynamic equilibrium?

Forward and backward reaction in a reversible reaction are at the same rate but there is always continuous movement.

What is Kc?

equilibrium constants of products/ equilibrium constants of reactants


The bigger the equilibrium constant...

The further over to the right the position of equilibrium

(products favoured over reactants)

What is Kc?:

aA + bB --> cC + dD

[C]^c + [D]^d / [A]^a + [B]^b

What are the units of Kc?

Varies depending on the orders of species

What don't you take into account when calculating Kc?


Why is Kc constant and what is the only factor that changes it?

Kc is a mere ratio of products and reactants in a reaction at equilibrium.


What type of reaction does raising temperature favour?


Why doesn't a catalyst affect Kc?

Catalyst affects the rate of both the forward and backward reaction equally, the position of equilibrium is not affected and so the ratio Kc will not change

How does increasing temperature affect Kc of an exothermic reaction?

Decreases Kc

How does increasing temperature affect Kc of an endothermic reaction?

Increases Kc

What is an acid?

Substance that donates protons (H ions)

What is a base?

Substance that accepts a proton

What is the name of the acid and base reacting in pairs?

Conjugate base/acid

State the two equations showing how water ionises by itself

H20 --> H+ + OH-

H20 + H20 --> H30+ + OH-

What is Kw and what is its value?

Ionic product of water


What is pH?


Does a smaller or larger concentration of H+ ions lead to a smaller pH?


What difference in H+ ion concentration does a difference of 1 in the pH mean?


Is the ionisation of water exothermic or endothermic and why?


Energy is required to break the bonds so that it can dissociate

How does the value of Kw change when you increase temperature?


Position of equilibrium of ionisation/dissociation of water is shifted over to the right because it is endothermic, producing more products

At higher temperatures does the pH of water get higher or lower? Why isn't it actually acidic/alkaline?


Equal concentration of H+ ions and OH- ions so the water is still neutral

Equation for Kw

[H+][OH-] = 1X10^-14

Equation for working out [H+] in a buffer solution

Ka x [acid]/[salt]

How do you work out pH for a weak acid?

[H+] = (sq root){Ka x [HA]}

pH = -log[H+]

How do you work out the pH for a strong acid?

[HA] = [H+]

pH = log[H+]

How do you work out Ka for a weak acid?

= [H+]^2/[HA]

How do you work out the pH of a strong base?

[H+] = Kw/[OH-]

pH = -log[H+]

When doing calculations involving dilutions what changes and what doesn't?



v=changes to total volume

Monoprotic acid

Donates one proton per mole of acid

Diprotic acid

Donates two protons per mole of acid


Substance that act as either an acid or a base

Strong acid

Fully dissociates in solution

Weak acid

Partially dissociates in solution

What does a large pKa signify?

Weak acid

What side does the position of equilibrium lie for strong/weak acids?

Strong acid = right, forward reaction is favoured

Weak acid = left, backward reaction is favoured

What are the units for Kw?


How do we identify an acid in a reaction?

Donates a proton, becoming negative

How do we identify the base in a reaction?

Accepts a proton, becoming positive

What is dissociation?

Breaking of covalent bonds

Equivalence point

When a solution becomes neutralised

End point

When the indicator changes colour

Describe rules of pH curves

Starts at pH of acid, not at 0

Buffering zone present in weak acid-strong base

Vertical line indicates equivalence point (this isn't present on weak acid-weak base curve)

Finishes at pH of base

Why can't we do a titration using a weak acid-weak base?

No definite end point - no vertical section on pH curve


pH sensitive compound (weak acid) that can exist in two different colours

Working range

range of pH that an indicator can change colour in

Half equivalence

Half of acid is neutralised and formed a salt


Ka = [H+]

pKa = pH

When do you use phenolpthalein/ methyl orange?

Phenolpthalein = strong base

methyl orange = weak base (but not with weak acid)

Buffer solution

Solution which prevents the change of pH upon additions of small volumes of acid/alkali

How many decimal points are used for pH?


Acidic buffer solution

ethanoic acid and sodium ethanoate

(weak acid and salt of that acid)

Basic buffer solution

ammonia and ammonium chloride


Same structural formula but different arrangement of atoms in space

What colour is phenolpthalein in alkaline conditions?


What colour is phenolpthalein in acidic conditions?


What colour is methyl orange in acidic conditions?


What colour is methyl orange in alkaline conditions?


Name the two types of stereoisomerism



What causes E-Z stereoisomerism?

Unable to rotate around a double bond

Z = same

E = opposite

What causes optical isomerism?

Four different substituents attached to one carbon atom resulting in a pair of non-superimposible enantiomers

They rotate polarised light in opposite directions


Pair of chiral isomers


Optical isomers

How do we measure optical rotation?


What is + / - mean for optical isomers?

+ = isomer rotates polarised light in a clockwise direction

- = isomer rotates polarised light in an anticlockwise direction

Racemic mixture/racemate

contains equal quantities of each enantiomer of an optically active compound

What type of reaction/mechanism is required for the synthesis of racemates?

Nucleophilic addition across C=O of planar compound (where attack from either side is equally likely) using hydrogen cyanide

Why aren't racemates optically active?

Optical activity of each enantiomer cancel each other out

What are the solutions and problems of using a racemic mixture as a drug?

One isomer may be ineffective/dangerous:

Seperate the two isomers to produce a pure form but this is difficult and expensive

Sell the useless isomer form but this is wasteful

What is the chiral centre?

Central carbon which is attached to four different substituents

What is the product called formed by nucleophilic addition of HCN?


Why are the boiling points of carbonyl compounds higher than in alkanes?

Dipole-dipole intermolecular forces in C=O carbonyl group whereas electronegativity of C-H in alkanes are too similar so only weaker Van der Waal forces present

Why are the boiling points of carbonyl compounds weaker than in alcohols?

Alcohols contain stronger hydrogen bonds than the permanent dipole-dipole intermolecular force

Are carbonyls soluble or insoluble?


Hydrogen bonds form with electronegative O atom in carbonyl group

What is formed when a nitrile is hydrolysed?

Carboxylic acid is formed

What is the reaction called which introduces a CH3CO group?


Give two advantages of using acid anhydrides rather than acyl chlorides


Less corrosive (HCl not produced)

What conditions are required for nucleophilic addition of carbonyl compounds using HCN?

Reflux in alkaline conditions

What is Tollens' reagent?

Ammoniacal silver nitrate

Why won't you ever carry out an experiment with CN-?


Why is nucleophilic addition of CN- on aldehydes/ketones useful for organic synthesis?

Increases carbon chain length

How and what are aldehydes oxidised to?

Carboxylic acid

acidified potassium dichromate - changes from orange to green

Is it oxidation or reduction when aldehydes become carboxylic acids?


Why can't ketones be easily oxidised?

Requires a C-C bond to break

What two tests can be used to distinguish aldehydes from ketones?

1. Fehling's:

Copper oxide is reduced to red copper precipitate as aldehyde is oxidised to a carboxylic acid

2. Tollens':

Silver is reduced to form a shiny mirror precipitate as aldehyde is oxidised to a carboxylic acid

Ketones give no reaction to both tests

What reducing agent is used for aldehydes and ketones?

Sodium tetrahydridoborate (III)


What is the nucleophile in reduction reactions of aldehyde/ketone?

Hydride (H-)

What conditions are required for the reduction of aldehyde/ketone?

Aqueous solution of NaBH4

NaBH4 provides hydride nucleophile

Water provides proton

What is an aldehyde reduced to form?

Primary alcohol

What is a ketone reduced to form?

Secondary alcohol

Are carboxylic acids soluble in water?

Yes - hydrogen bonds can form at C=O bond

What are carboxylic acids isomeric with?


Why are carboxylic acids acidic?

Contains hydrogen atom in functional group which it can donate.

How can carboxylic acids be distinguished from any other functional group?

React with sodium cabronate to release CO2.

How do the boiling points of carboxylic acids change as they increase in size?

Also increase due to the increasing size of Van der Waal intermolecular forces

What is formed when a carboxylic acid reacts with an alkali ?

Water and an ionic salt

Conditions required for esterification

Alcohol and carboxylic acid in presence of strong acidic catalyst (sulfuric acid)

Produces ester and water

This is a reversible reaction which produces a mixture of products and reactants

What is formed when a carboxylic acid loses a proton?

Carboxylate ion is produced which is stable due to the delocalisation of the negative charge over the whole group

Conditions required for hydrolysis of ester

ester and water in presence of strong acidic catalyst (sulfuric acid) to produce a carboxylic acid and alcohol.

Reversible reaction producing an equilibrium mixture


ester and aqueous NaOH to produce salt and alcohol

What is the formula of glycerol?


How do you name esters?

Alkyl group that replaced the hydrogen from when it was a carboxylic acid goes first

Parent acid dictates the -oate end

What is formed when a carboxylic acid reacts with sodium hydrogencarbonate?

Salt and water and carbon dioxide

How can you convert a carboxylate salt into a fatty acid?

Add HCl

What is glycerol used for?

Food colourings

Prevent ointments drying out

Plasticise materials

Describe saponification

Alkaline hydrolysis of triglycerides to produce sodium salts (soap)

Ester is boiled in sodium hydroxide to produce glycerol and sodium salt

State reaction for producing biodiesel

Triester and methanol react to produce a methylester and glycerol

What type of reactions take place for acylation to occur?


What is produced when acyl group reacts with ammonia?


What is produced when an acyl group reacts with a primary amine?

N-substituted amide

What is produced when an acyl group reacts with an alcohol?


What is produced when an acyl group reacts with water?

Carboxylic acid

What makes acid chloride a good acylating agent?

Chlorine atom is very electronegative and so withdraws electrons from carbonyl carbon making the carbon more positive and thus open for attack.

State reactivity of nucleophiles in addition-elimination reactions

Ammonia - produce amide

Amine - produce N-sub-amide

Alcohol - produce ester

Water - produce carboxylic acid

What do acid anhydrides produce in acylation reaction which differs from acyl chlorides?

Acid anhydrides produce carboxylic acids

Acyl chlorides produce HCl


Electron pair donor

Describe the structure of benzene

Planar regular hexagon of carbon atoms, each of which is bonded to a single hydrogen atom

Explain the aromatic stability of benzene

Electrons are delocalised in a ring where they are spread over more than two atoms forming a pi-bond of high electron density.

Problems with Kekule's model of benzene

He thought that there would be three double carbon bonds but if there were it should readily undergo electrophilic addition

Hydrogenation should be thrice of cyclohexane's but it is less, proving that it is more stable

X-ray crystallography showed that the structure of benzene to have bonds of all equal length. Kekule's model would have been assymetrical.

Conditions required for nitration of arene

Concentrated nitric acid and concentrated sulfuric acid produces electrophile (NO2+)

How can we tell that an arene is being combusted?

Smokey flame due to high carbon:hydrogen ratio

What is the electrophile for nitration reactions?

Nitronium ion


State equations for formation of electrophile for nitration of arene

HNO3 + H2SO4 -->HSO4- + H2NO3+

H2NO3+ --> NO2+ + H2O

What is the catalyst for Friedel-Crafts acylation reactions

Aluminium chloride


State equation of catalyst formation for Friedel-Crafts reaction

AlCl3 + RCOCl --> RCO+ + AlCl4-

What is the formula and when is the acylium ion involved?


used in Friedel-Craft reaction for formation of electrophile aluminium chloride AlCl4

Conditions for Friedel-Crafts acylation

Acyl chloride and anhydrous aluminum chloride catalyst

Electrophile = acylium RCO+

What are quaternary ammoniu salts used for?

Fabric softener

How many hydrogens are attached to the nitrogen atom on a primary amine?


How many hydrogens are attached to the nitrogen atom on a secondary amine?


State three ways of preparing amines

1. Successive nucleophilic substitution using excess ammonia on haloalkanes

2.Reducing nitriles using a nickel catalyst

3.Making phenylamine

Do amines have a higher or lower boiling point and why?


Nitrogen is less electronegative than oxygen and so the hydrogen bonds intermolecular forces are weaker and thus require less energy in order to be overcome

Are amines soluble in water? What is the exception?

Yes, hydrogen bonds can form

Phenylamine isn't due to the benzene ring

What is formed when an amine reacts with an acid

Ionic salt

Amine acts as a base

How can we regenerate the amine from its ionic salt

use a strong base like sodium hydroxide

Explain base strengths of amines

Alkyl group's inductive effect feeds electrons towards the nitrogen atom making its lone pair more exposed for attaching onto a H+ ion

Secondary alkylamine is a stronger base than a primary alkylamine

Arylamines are the weakest bases because the aryl group's inductive effect feeds away from the nitrogen atom.

What is the downside of amine preparation via nucleophilic substitution and how can this be overcome?

Sucessive and so a mixture of different amines are produced

However, these can be seperated via fractional distillation