A Level Chemistry: Acids, Bases, and Water of Crystallisation

Comprehensive flashcards covering common acids and bases, pH definitions, neutralisation reactions, titration procedures, and hydrated salt calculations based on the A Level Chemistry module 2.1.4.

How are acids and alkalis defined in terms of the ions they release in aqueous solution?

Acids release $H^+$ ions (proton donors) and alkalis release $OH^-$ ions.

Name the four common acids and three common alkalis identified in the specification.

Acids: Hydrochloric acid ($HCl$), Sulfuric acid ($H_2SO_4$), Nitric acid ($HNO_3$), and Ethanoic acid ($CH_3COOH$); Alkalis: Sodium hydroxide ($NaOH$), Potassium hydroxide ($KOH$), and Ammonia ($NH_3$).

Why does hydrogen fluoride ($HF$) have a higher boiling point than hydrogen chloride ($HCl$)?

Both have induced dipole dipole interactions (IDDI) and permanent dipole dipole interactions (PDDI), but $HF$ also has hydrogen bonding. More energy is needed to overcome hydrogen bonding than PDDI.

Define strong and weak acids in terms of dissociation.

Strong acids completely dissociate in aqueous solution (e.g., $HCl(aq) \rightarrow H^+(aq) + Cl^-(aq)$), while weak acids only partially dissociate (e.g., $CH_3COOH(aq) \rightleftharpoons H^+(aq) + CH_3COO^-(aq)$).

What is the difference between a base and an alkali?

A base is a proton ($H^+$) acceptor that neutralises acids to form salts; an alkali is a specific type of base that dissolves in water, releasing hydroxide ($OH^-$) ions.

What is the bond angle and shape of the ammonium ion ($NH_4^+$)?

The bond angle is $109.5^\text{o}$ because the Nitrogen atom has 4 bonding pairs and no lone pairs, and electron pairs repel to get as far apart as possible.

What are the products of a reaction between an acid and a metal carbonate?

The products are a salt, water, and carbon dioxide ($CO_2$).

Define neutralisation and provide the ionic equation for the reaction between an aqueous acid and an alkali.

Neutralisation is the reaction of an acid with a base to form a salt and water; the ionic equation is $H^+(aq) + OH^-(aq) \rightarrow H_2O(l)$.

What are spectator ions in a chemical reaction?

Spectator ions are ions that are the same on both sides of a balanced equation and do not participate in the reaction; they are cancelled out when deriving an ionic equation.

Outline the steps to prepare a $250\text{ cm}^3$ standard solution from a solid acid.

1. Weigh the solid by difference into a beaker. 2. Dissolve in distilled water. 3. Transfer to a volumetric flask using a funnel. 4. Rinse the beaker and funnel into the flask. 5. Add water to the graduation line (dropwise at the end). 6. Stopper and mix by inversion.

Define the terms hydrated, anhydrous, and water of crystallisation.

Hydrated refers to crystalline salts containing water; anhydrous refers to the salt after the water has been removed; water of crystallisation is the water molecules that are part of the crystalline structure of a hydrated salt.

How is the water of crystallisation removal quantified experimentally?

By heating the hydrated salt in a crucible until the mass remains constant when the solid is cooled.

According to the student activities, what is the formula for the hydrated salt if $5.56\text{ g}$ of iron(II) sulfate crystals form $3.04\text{ g}$ of anhydrous salt ($M_r \text{ FeSO}_4 = 151.9\text{ g mol}^{-1}$)?

$$FeSO_4 \times 7H_2O$$

What is the ionic equation for the reaction between a carbonate solution and dilute acid?

$$CO_3^{2-}(aq) + 2H^+(aq) \rightarrow H_2O(l) + CO_2(g)$$

Compare the melting points of Ammonia ($-78^\text{o}C$) and Ammonium sulfate ($230^\text{o}C$).

Ammonia is a simple covalent molecule with weak intermolecular hydrogen bonds. Ammonium sulfate is a giant ionic lattice with strong electrostatic attractions between oppositely charged ions, requiring significantly more energy to break.