Organic Chemistry + Titration Graphs

Question 1

What are Fehling’s and Tollen’s reagents normally used for?

Answer 1

Used to distinguish between aldehydes and ketones

Question 2

How can one deduce if it is a primary or secondary alcohol?

Answer 2

The product of light oxidation- aldehyde and ketone - are tested with Fehling’s and Tollen’s reagents.

For Fehling’s:
Positive test (brick-red precipitate) with aldehydes
Negative test (no precipitate) with ketones (except alpha-hydroxy ketones)

For Tollen’s:
Positive test (formation of a ‘silver mirror’ or black precipitate) with aldehydes
Negative test (no precipitate) with ketones (except alpha-hydroxy ketones)

Question 3

What happens in Tollen’s and Fehling’s reagents normally reactions?

Answer 3

For Fehling’s:
Positive test (brick-red precipitate) with aldehydes
Negative test (no precipitate) with ketones (except alpha-hydroxy ketones)

For Tollen’s:
Positive test (formation of a ‘silver mirror’ or black precipitate) with aldehydes
Negative test (no precipitate) with ketones (except alpha-hydroxy ketones)

Question 4

What is the balanced equation for the reaction between Fe²⁺ and MnO₄⁻ in acidic conditions?

Answer 4

5Fe2+ + MnO4- + 8H+ —> 5 Fe 3+ + Mn2+ + 4H2O

Question 5

What is the equivalence point in a titration of a strong acid with a strong base?

Answer 5

The point where the number of moles of H⁺ equals the number of moles of OH⁻, typically indicated by a steep pH increase near pH 7.

Question 6

How does a buffer solution resist changes in pH?

Answer 6

It contains a weak acid and its conjugate base (or a weak base and its conjugate acid) that neutralize small amounts of added acid or base.

Question 7

How do you calculate the solubility product (Ksp)?

Answer 7

Use the concentrations of the ions at equilibrium to calculate ksp

Ksp= [Ca2+][OH-]^2

Question 8

What is the equivalence point for a weak acid/strong base titration?

Answer 8

The equivalence point occurs when all the weak acid has been neutralized by the strong base. The pH at the equivalence point will be greater than 7 due to the basic nature of the conjugate base.

Question 9

What is the pH at the half-equivalence point for a weak acid/strong base titration?

Answer 9

At the half-equivalence point, the pH equals the ( pK_a ) of the weak acid, as the concentrations of the acid and its conjugate base are equal.

Question 10

What is the equivalence point for a weak base/strong acid titration?

Answer 10

The equivalence point occurs when all the weak base has been neutralized by the strong acid. The pH at the equivalence point will be less than 7 due to the acidic nature of the conjugate acid.

Question 11

What is the pH at the half-equivalence point for a weak base/strong acid titration?

Answer 11

At the half-equivalence point, the pH equals the ( pK_b ) of the weak base, as the concentrations of the base and its conjugate acid are equal.

Question 12

What is the characteristic shape of the titration curve for a weak acid/strong base titration?

Answer 12

The curve starts with a gradual rise in pH, followed by a buffer region, a steep rise near the equivalence point, and then levels off in the basic range.

Question 13

What is the characteristic shape of the titration curve for a weak base/strong acid titration?

Answer 13

The curve starts in the basic pH range, shows a buffer region, and then drops steeply near the equivalence point, leveling off in the acidic range.

Question 14

What is the equivalence point for a strong acid/weak base titration?

Answer 14

The equivalence point is where the strong acid has fully neutralized the weak base, with a resulting pH less than 7.

Question 15

How does the buffer region appear on a titration curve for a weak acid/strong base?

Answer 15

The buffer region appears as a relatively flat part of the curve where pH changes slowly, occurring before the steep rise to the equivalence point.

Question 16

TF

Fehling’s reagent can be used to test for the presence of aldehydes.

Answer 16

True

Question 17

TF

Tollens’ reagent gives a positive result with both aldehydes and ketones.

Answer 17

False

Question 18

TF

A positive Tollens’ test results in the formation of a silver mirror on the inner surface of the test tube.

Answer 18

True

Question 19

TF

Fehling’s reagent is blue because it contains copper(II) ions.

Answer 19

True

Question 20

TF

Both Fehling’s and Tollens’ reagents can oxidize alcohols to carboxylic acids.

Answer 20

False

Question 21

TF

Tollens’ reagent contains ammonia and silver nitrate.

Answer 21

True

Question 22

TF

Fehling’s reagent gives a red precipitate when it reacts with ketones.

Answer 22

False

Question 23

TF

Tollens’ reagent is sensitive to light and should be used freshly prepared.

Answer 23

True

Question 24

TF

A positive Fehling’s test indicates the presence of a reducing sugar.

Answer 24

True

Question 25

TF Ketones typically give a positive result with Fehling’s reagent.

Answer 25

False

Question 26

TF At equilibrium, the concentrations of reactants and products remain constant over time.

Answer 26

True

Question 27

TF In an equilibrium graph, a horizontal line indicates a reaction has reached dynamic equilibrium.

Answer 27

True

Question 28

TF A shift in the equilibrium position due to a change in concentration is shown as a plateau on the graph.

Answer 28

False

Question 29

TF An increase in temperature for an exothermic reaction shifts the equilibrium curve upward toward the reactants.

Answer 29

True

Question 30

TF Equilibrium graphs only show the forward reaction rate decreasing over time.

Answer 30

False

Question 31

TF In an equilibrium graph, the rates of the forward and reverse reactions become equal at equilibrium.

Answer 31

True

Question 32

TF If a catalyst is added, the equilibrium graph shows a change in the equilibrium position.

Answer 32

False

Question 33

TF An increase in pressure will shift the equilibrium graph towards the side with fewer moles of gas.

Answer 33

True

Question 34

TF The equilibrium constant \( K \) can be directly determined from the shape of the equilibrium graph.

Answer 34

False

Question 35

TF In an equilibrium graph, a sudden change in concentration is shown as a sharp spike or drop in the curve.

Answer 35

True

Question 36

What is the difference between primary, secondary, and tertiary alcohols?

Answer 36

A primary alcohol has one alkyl group attached to the carbon bonded to the hydroxyl group (-OH), a secondary alcohol has two, and a tertiary alcohol has three.

Question 37

What is esterification?

Answer 37

Esterification is the reaction between a carboxylic acid and an alcohol to form an ester, typically in the presence of an acid catalyst.

Question 38

What is a primary alcohol?

Answer 38

А primary alcohol is one where the hydroxyl group (-OH) is attached to a carbon that is bonded to only one other carbon (or no other carbons).

Question 39

What happens when a primary alcohol is oxidized?

Answer 39

A primary alcohol can be oxidized to an aldehyde, and if further oxidized, to a carboxylic acid.

Question 40

What conditions need to be satisfied for a primary alcohol to oxidise to an aldehyde? A carboxylic acid?

Answer 40

For oxidation to aldehyde form, a limiting oxidising agent have to be used. Some examples - PCC ( pyridinium chlorochromate) or DMP (Dess-Martin periodinane) For oxidation to carboxylic acid form, the reaction has to occur in high temperatures , using reflux. Reflux involves heating the reaction mixture to boiling and condensing the vapour back into the liquid phase, allowing the reaction to proceed for an extended period without loss of solvent or reactants.

Question 41

What is reflux?

Answer 41

Reflux involves heating the reaction mixture to boiling and condensing the vapour back into the liquid phase, allowing the reaction to proceed for an extended period without loss of solvent or reactants.

Question 42

What is a secondary alcohol?

Answer 42

A secondary alcohol has the hydroxyl group attached to a carbon that is bonded to two other carbons.

Question 43

Can tertiary alcohols be oxidized easily?

Answer 43

No, tertiary alcohols generally do not undergo oxidation because there is no hydrogen attached to the carbon bonded to the hydroxyl group.

Question 44

How do aldehydes react with Tollens’ reagent?

Answer 44

Aldehydes are oxidized by Tollens' reagent, which produces a silver mirror on the surface of the container.

Question 45

What is esterification?

Answer 45

Esterification is the reaction between a carboxylic acid and an alcohol to form an ester and water.

Question 46

How do you synthesize a polyester?

Answer 46

A polyester is synthesized by the condensation of a diol and a dicarboxylic acid, releasing water in the process.

Question 47

What is the effect of inductive effects on carboxylic acid strength?

Answer 47

Electron-withdrawing substituents, such as halogens, increase the strength of carboxylic acids by stabilizing the conjugate base.

Question 48

How do ester bonds in polyesters influence the structure of the polymer?

Answer 48

The ester bonds in polyesters create long, repeating chains, which give the polymer its strength and flexibility.

Question 49

What is the significance of resonance in the acidity of carboxylic acids?

Answer 49

The resonance stabilization of the carboxylate anion (the conjugate base) makes carboxylic acids relatively strong acids.

Question 50

Describe the process of ester hydrolysis and how it differs from esterification.

Answer 50

Ester hydrolysis is the reverse reaction of esterification, where an ester reacts with water to break the ester bond, producing an alcohol and a carboxylic acid. In esterification, a carboxylic acid and an alcohol react to form an ester and water. Hydrolysis requires water and typically occurs under acidic or basic conditions.