Chemistry AQA

E v e r y t h i n g

What product is formed from the gentle heating of a primary alcohol?

An aldehyde is formed. (Oxidation reaction, + [O])

R–CH2​OH + [O] → R–CHO + H2​O

What product is formed from a primary alcohol when heated under reflux?

A carboxylic acid is formed. (Oxidation reaction, + [O])

R–CHO + [O] → R–COOH

What reagent is used for the formation of aldehydes and carboxylic acids from a primary alcohol?

Acidified potassium dichromate (K2Cr2O7). (This is the oxidising agent, the alcohol is the reducing agent.)

What classes of alcohols react with acidified potassium dichromate and what is observed?

Primary and secondary alcohols react, tertiary alcohols do not.

A colour change from orange to green is observed.

What is the chemical reagent used to confirm the presence of a carboxylic acid and what is observed?

Sodium carbonate/hydrogencarbonate (Na2CO3 / NaHCO3), produces CO2, effervescence.

(Limewater turns colourless to milky when CO2 bubbled through.)

What is the name of the process where glucose forms ethanol and what conditions are necessary?

Fermentation, no oxygen present, yeast must be present.

What are stereoisomers?

Stereoisomers are molecules with the same structural and molecular formulae but have their atoms arranged differently in space.

Are primary or tertiary carbocations more stable?

Tertiary carbocations are more stable, therefore often form more readily as a major product.

What is the reagent to turn a ketone back into an alcohol?

NaBH4, is the reducing agent, reduces the ketone. (NaBH4 itself is oxidised).

R–CO–R’ + 2[H] → ​​R–CHOH–R’

Definition of standard enthalpy change of combustion.

Enthalpy change when 1 mole of substance is burned in excess oxygen with all reactants and products in standard states.

State the meaning of hydration.

Addition of water.

Define mean bond enthalpy.

Enthalpy change needed to break covalent bonds averaged over a range of molecules.

What alcohol and carboxylic acid is used to form the ester methyl ethanoate + water. What catalyst is required for this reaction?

The acid ethanoic acid and the alcohol methanol. Strong acid catalyst required. (e.g. H2SO4, H+ Required, done under reflux.)

Carboxylic acid + Alcohol ⇌ Ester + Water

State in general terms how a catalyst works.

Catalyst provides an alternative mechanism for a reaction that has a lower activation energy.

What products are formed when a carboxylic acid reacts with sodium hydroxide?

Sodium salt and water.

R–COOH + NaOH → R–COO−Na+ + H2​O

(Acid-base neutralisation.)

What does an acid anhydride and alcohol react to make?

Produces an ester and carboxylic acid.

E.g. Ethanoic anhydride + Methanol → Methyl Ethanoate + Ethanoic Acid

What does an acyl chloride and alcohol produce?

Produces an ester and HCL

E.g. Ethanoyl Chloride + Methanol → Methyl Ethanoate + HCL

How is biodiesel created from a fat/oil ester and methanol, what are the products?

Glycerol and methyl esters are produced. Long chain methyl esters are used as biodiesel.

Fat/Oil + 3 Methanol → Glycerol + 3 Methyl ester

What is the reaction between propanal and HCN? Name products.

Produces 2-hydroxybutanenitrile.

What is produced from the hydrolysis of an ester in the presence of concentrated H2SO4 catalyst and performed under reflux?

A carboxylic acid and alcohol is produced.

Ester + Water ⇌ Carboxylic acid + Alcohol

What is the test for confirming the presence of acyl chlorides?

Silver nitrate solution, white precipitate is formed. (AgCl)

What does an aldehyde and HCN react to from?

A hydroxynitrile.

(Requires slight alkaline conditions).

What is a pair of enantiomers?

Two stereoisomers that have different arrangement of atoms in space around a chiral carbon atom.

(The two are mirror images when the structures are compared, and can both rotate plane polarised light in different directions.)

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

An N substituted amide and HCl is formed.

(Substituted amide functional group is R-C(=O)-NH-R’. Amide group is C(=O)-NH2.)

What does an acyl chloride and ammonia react to produce?

An amide (NH2 functional group) and HCl.

What is produced from salicylic acid and ethanoic anhydride?

Aspirin and ethanoic acid.

Why may a reaction have a small enthalpy change?

Similar types of bonds may have been broken/made and the same number of bonds must’ve been broken/made.

Why is a minimum amount of solvent used when purifying a substance via recrystallisation?

Why is it filtered hot?

To form a saturated (or highly concentrated) solution.

Filtered hot to prevent crystallisation during filtration.

What is the enthalpy of hydration?

When 1 mole of gaseous ions is converted into 1 mole of aqueous ions.

Define the term enthalpy change.

Heat change at constant pressure.

What compound is used for the salt bridge in electrode potentials?

Potassium nitrate.

What 2 reagents are needed to produce the electrophile NO2+ for the nitration of benzene.

Conc H2SO4 and conc HNO3.

HNO3 + H2SO4 → HSO4- + (NO2+) + H2O

Whats the reducing agent to turn an NO2 on a benzene ring into NH2?

H2 and Pt catalyst.

Reducing agent for benzene ring into cyclohexane?

H2 and Pt catalyst.

Why do molecules that contain one element have 0 enthalpy of formation? (e.g. Δ𝐻f H2 = 0)

Molecule already exists within its standard state.

At what temperature does entropy = 0 for any substance?

0K

Products of 2NaBr + 2H2SO4?

Na2SO4 + Br2 + SO2 + H2O.