Stpm Inorganic Chemistry: Aluminium

Modern ceramics are known for their high melting point, application in engineering, and being very hard. However, they do not corrode readily. This is because ceramics are typically made from inorganic materials that are resistant to chemical reactions and corrosion. They are stable and durable, making them suitable for various applications in industries such as aerospace, automotive, and electronics.

The slow reaction is the reaction between the oxide layer and hydrochloric acid. Once the oxide layer is used up and the pure aluminium is exposed a vigorous reaction between aluminium and hydrochloric acid will take place.

An aqueous solution of Al3+ is acidic. Hence the pH value will be lesser than 7

The correct answer is "There are two coordinate covalent bonds in the molecule." This is because dimer Al2Cl6 consists of two aluminum atoms bonded to each other through two coordinate covalent bonds. In a coordinate covalent bond, one atom donates a pair of electrons to the other atom, forming a bond. In this case, the chlorine atoms act as Lewis bases, donating their lone pairs of electrons to the aluminum atoms, which act as Lewis acids. Therefore, the statement is true.

Aluminium fluoride is an ionic compound because it is formed by the transfer of electrons from aluminium to fluorine, resulting in the formation of positively charged aluminium ions and negatively charged fluoride ions. On the other hand, aluminium chloride is a covalent compound because it is formed by the sharing of electrons between aluminium and chlorine atoms.

With concentrated nitric acid, the aluminium metal is being oxidised causing the thickening of the aluminium oxide layer.

2[Al(H2O)6]3+ (aq) + 3S2- (aq) → 2Al(OH)3.3H2O (s) + 3H2S(g)

In the the salt solutions the complex aluminium ion behave accordingly:
[Al(H2O)6]3+ (aq) + H2O (l) ↔ [Al(H2O)5(OH)]2+ + H3O+ (aq)

The high current is used to keep the temperature of the electrolysis cell at 900 oC. This is because the extraction of aluminium from bauxite is an endothermic process, meaning it requires heat to proceed. By passing a high current through the cell, resistance in the cell generates heat, which helps to maintain the desired temperature of 900 oC.

Aluminium reacts with aqueous potassium hydroxide to form the aluminate ion and hydrogen gas

Normally, a layer of aluminium oxide is found on the surface of aluminium metal.. This oxide layer is removed by mercury(II) chloride. Aluminium will react with water to form a white precipitate of aluminium hydroxide and hydrogen gas.

Aluminium oxide is impermeable and non porous. hence it is insoluble in water.

Alum is used to bind dyes

In aqueous solution, Al3+ ion exist as an octahedral complex [Al(H2O)6]3+ .

Aluminium fluoride exist as an ionic compound. Hence high energy is needed to overcome the electrstatic force between the Al3+ and F- ions.