Explanation​:
Indicators are weak acids or bases where the components of their conjugate base/acid have different colours.

Explanation:
Cathode site of reduction, anode site of oxidation, use CROA to remember this.
Reduction is the gain of electrons.

Explanation:​
Water accepts a hydrogen ion to produce H3O^+. This question is easy as the formation of H3O^+ is covered explicitly in the syllabus.

Explanation​:
An acidic buffer solution contains a weak acid and the salt of its conjugate base.

Explanation​:
Statement II is incorrect as acids produce solutions with $\mathrm{pH}$ lower than 7.

Explanation:​
NaOH is a base so reacts with a hydrogen ion. HNO3​, nitric acid, releases a hydrogen ion through the breaking (heterolysis) of the O-H bond.
This question is moderately difficult as the student must recognise that NaOH is a base and HNO3​ an acid and correctly interpret a structural formula that may be unfamiliar.

Explanation​:
Use the mnemomic CNAP; cathode negative, anode positive for the polarity in electrolytic cells.

Explanation:​

Acids react with carbonates to produce a salt, water, and carbon dioxide.

Explanation:​
The student must identify the reagents and conditions for three reactions. Only information stated explicitly in the syllabus is needed and no interpretation of structural formulas is required. This question is therefore, categorized as “easy”.
Alkenes react with HCl in an addition reaction, alkanes react with halogens in the presence of UV light through free radical substitution, and halogenoalkanes react with NaOH in a nucleophilic substitution reaction.

Explanation​:
$\mathrm{l}$ is a neutral salt, Na2CO3 is a basic salt, and NaOH is a strong base.

Explanation​:
The student must be sufficiently familiar with the reactions covered in the syllabus to realize that sodium hydroxide would not be useful for producing a diol from an alkene. Alternatively, the question could be answered by recalling the use of sodium hydroxide in the other three reactions. The question is categorized as easy as only limited knowledge of reactions in the literature is needed.
Reactions B and C are both acid-base reactions where NaOH deprotonates the organic species.
Reaction D is a nucleophilic substitution of a halogenoalkane with OH− as the nucleophile.
Reaction A would require first halogenation (with e.g. Br2​) followed by nucleophilic substitution.

Explanation​:
Recall of the nitration intermediate covered in the syllabus. This is formed after the NO2^+ electrophile has been attacked by benzene’s pi electrons.

Explanation​:
Non-spontaneous reactions take place in electrolytic cells using an external power supply.
The positive electrode is the anode where oxidation takes place.
The aqueous metal ion (Mx^+) is reduced at the cathode to produce the solid metal.

Explanation:​
Spontaneous reactions occur in voltaic cells converting chemical energy to electrical energy, whereas, non-spontaneous reactions occur in electrolytic cells requiring electrical energy and converting this to chemical energy.
Electrolytic cells typically consist of one reaction vessel containing the aqueous of molten electrolyte. No salt bridge is therefore required.

Explanation:​
ΔGθ = $-$.
For spontaneous reactions, ΔGθ is negative, therefore Ecellθ​ must be positive.

Explanation:​
C3H8 is a saturated alkane and C3H6 is an unsaturated alkene. The test of unsaturation using Br2(aq) can demonstrate the presence or absence of a carbon-carbon double bond.
In the presence of a double bond, Br2(aq) can add across the double bond in the alkene producing a dibromo-alkane, and a change of color from brown to colorless will be observed.
In the case of the absence of a double bond (saturated hydrocarbon), no color change would occur.

Explanation:​
In electroplating, the anode is made of silver metal, which is oxidized to Ag^+ ions. The Ag^+ ions are then reduced at the cathode to Ag metal, resulting in a coating around this object.
Any impurities will sink to the bottom of the vessel.
In electrolytic cells, the anode is positive, and the cathode is negative. As a result, electrons travel from positive to negative.

Explanation:​

Metals and acids react to produce a salt and hydrogen gas. The formulae of the ions are Mg^2+ and NO3^−, therefore for a neutral salt, two nitrate ions are required for each magnesium ion.

Explanation:​

A 1.0M solution of KOH would have a pH of 14. Methyl orange, bromocresol green, and phenolphthalein would be orange, yellow, and green respectively at this pH.