Question

Write balanced equations to represent (a) the displacement of a halide anion from aqueous solution by liquid bromine (b) the reaction with water of an alkali metal with \(Z>50\) (c) the reaction of tetraphosphorus decoxide with water (d) the reaction of aluminum oxide with aqueous sulfuric acid

Short answer

The balanced equations for the mentioned reactions are: (a) \( 2KBr(aq) + Cl_2(g) \rightarrow 2KCl(aq) + Br_2(l) \) (b) \( 2Rb(s) + 2H_2O(l) \rightarrow 2RbOH(aq) + H_2(g) \)(c) \( P_4O_{10}(s) + 6H_2O(l) \rightarrow 4H_3PO_4(aq) \)(d) \( Al_2O_3(s) + 3H_2SO_4(aq) \rightarrow Al_2(SO_4)_3(aq) + 3H_2O(l) \)

Step-by-step solution

- Writing Displacement Reaction

In displacement reactions, one element is substituted for another in a compound. For the reaction 'displacement of a halide anion from aqueous solution by liquid bromine', the balanced chemical equation will be \( 2KBr(aq) + Cl_2(g) \rightarrow 2KCl(aq) + Br_2(l) \). Here, chlorine (a halide anion) displaces bromine with the help of potassium bromide (2KBr), thus forming liquid bromine.

- Reaction of Alkali Metal with Water

An alkali metal with \(Z>50\) refers to alkali metals from the periodic table with atomic numbers greater than 50. For instance, Rubidium (Rb) has an atomic number of 37, so it fits the condition. The reaction of an alkali metal with water always gives a basic solution. Hence, the balanced reaction equation can be formulated as \( 2Rb(s) + 2H_2O(l) \rightarrow 2RbOH(aq) + H_2(g) \), where Rb represents rubidium.

- Reaction of Tetraphosphorus Decoxide with Water

Tetraphosphorus decoxide (P4O10) reacts aggressively with water to produce phosphoric acid. The balanced chemical equation can be written as \( P_4O_{10}(s) + 6H_2O(l) \rightarrow 4H_3PO_4(aq) \) where H_3PO_4 is phosphoric acid.

- Reaction of Aluminum Oxide with Aqueous Sulfuric Acid

Aluminum oxide (Al2O3) reacts with sulfuric acid (H2SO4) to produce aluminum sulfate and water, being a classic example of an acid-base neutralization reaction. The balanced equation is \( Al_2O_3(s) + 3H_2SO_4(aq) \rightarrow Al_2(SO_4)_3(aq) + 3H_2O(l) \).

Key concepts

Displacement Reactions

Displacement reactions are fascinating chemical processes where one element displaces another in a compound. In these reactions, a more reactive element can replace a less reactive element from its compound. This concept is beautifully illustrated in the displacement of a halide anion from an aqueous solution by liquid bromine.
For example, consider the reaction: \( 2KBr(aq) + Cl_2(g) \rightarrow 2KCl(aq) + Br_2(l) \). Here, chlorine, which is more reactive than bromine, displaces bromine from potassium bromide to form potassium chloride and liquid bromine. Such reactions are common among halogens, with each halogen able to displace those below it on the periodic table.
It's important to remember that these reactions only occur when the free element is more reactive than the element it is trying to displace. This order of reactivity is crucial and is determined by the position of the elements in the periodic table.

Alkali Metals

Alkali metals, found in Group 1 of the periodic table, exhibit fascinating chemical properties. Known for their high reactivity, particularly with water, they produce a basic solution upon contact. When thinking of alkali metals reacting with water, envision the vigorous reaction and effervescent hydrogen gas produced.
The exercise highlights a reaction involving an alkali metal with an atomic number greater than 50. Rubidium, though not meeting this atomic criterion as it has an atomic number of 37, efficiently exemplifies the reactivity characteristic of alkali metals. The reaction with water is given as: \( 2Rb(s) + 2H_2O(l) \rightarrow 2RbOH(aq) + H_2(g) \).
When rubidium reacts with water, rubidium hydroxide (a strong base) and hydrogen gas are produced. This showcases the typical behavior of alkali metals and their tendency to form alkaline solutions.

Tetraphosphorus Decoxide

Tetraphosphorus decoxide, known chemically as \( P_4O_{10} \), is an intriguing compound, predominantly known for its reactivity with water to form phosphoric acid. This reaction is notably exothermic, meaning it releases heat.
The balanced chemical reaction is represented as: \( P_4O_{10}(s) + 6H_2O(l) \rightarrow 4H_3PO_4(aq) \). In this process, each molecule of tetraphosphorus decoxide reacts with six water molecules to produce four molecules of phosphoric acid.
This reaction underlines the nature of phosphorus pentoxide as a powerful dehydrating agent. In practical terms, this means it has strong attraction to water molecules, facilitating its use in various industrial applications where water removal is necessary.

Aluminum Oxide

Aluminum oxide, with the chemical formula \( Al_2O_3 \), is a noteworthy compound due to its wide range of applications and its behaviour in reactions. One such reaction is with sulfuric acid, which results in the formation of aluminum sulfate and water.
The chemical equation illustrating this classic acid-base neutralization is: \( Al_2O_3(s) + 3H_2SO_4(aq) \rightarrow Al_2(SO_4)_3(aq) + 3H_2O(l) \). In this process, aluminum oxide acts as a base, neutralizing sulfuric acid to yield aluminum sulfate, a compound commonly utilized in water purification processes.
Such reactions not only demonstrate the versatility of aluminum oxide but also highlight the balancing act of charges and molecules, ensuring mass conservation within chemical equations.