Write a plausible chemical equation to represent the...

Write a plausible chemical equation to represent the reaction of (a) $\mathrm{Cl}_{2}(\mathrm{g}) \quad$ with cold $\mathrm{NaOH}(\mathrm{aq})$ (b) NaI(s) with hot $\mathrm{H}_{2} \mathrm{SO}_{4}(\text { concd aq })$ $;$ (c) $\mathrm{Cl}_{2}(\mathrm{g})$ with $\mathrm{KI}_{3}(\mathrm{aq})$ (d) $\operatorname{NaBr}\left(\text { s) with hot } \mathrm{H}_{3} \mathrm{PO}_{4}\right.$ $(\operatorname{concd} a q) ;(e)$ $\mathrm{NaHSO}_{3}(\mathrm{aq})$ with $\mathrm{MnO}_{4}$ $4^{-}(a q)$ in dilute $\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq})$.

Key Concepts

Triiodide Equilibrium

In aqueous iodide/iodine systems, iodine can react with iodide ions to form the triiodide ion (I3–). This equilibrium is important because it affects the observed reactivity and color of the solution and must be accounted for when writing chemical equations that involve iodine species in redox or displacement reactions.

Disproportionation Reactions

A disproportionation reaction is one where a single element in one oxidation state is simultaneously oxidized and reduced to form two different products in which that element appears in different oxidation states. This concept explains reactions in which, for example, a halogen reacts with a base to yield both a halide and a hypohalite, demonstrating the dual role of the reactant.

Redox Reactions

Redox (reduction?oxidation) reactions involve the transfer of electrons between species, resulting in changes in oxidation numbers. Understanding how to break down a redox reaction into its oxidation and reduction half?reactions, balance them under acidic or basic conditions, and then combine them is essential for properly capturing the electron flow in processes such as those involving strong oxidants like permanganate.

Halogen Displacement Reactions

Halogen displacement reactions occur when a more reactive halogen replaces a less reactive one in a compound. This is rooted in the differences in electronegativity and standard electrode potentials among the halogens, and it underpins many reactions in inorganic chemistry where the reactivity of halogens in different oxidation states determines the products.

Stoichiometry and Chemical Equation Balancing

Accurate stoichiometry ensures that chemical equations obey the law of conservation of mass and charge. Balancing reactions, particularly those involving redox processes or multiple reaction pathways, is a fundamental skill that requires careful attention to the number of atoms of each element and the overall charge on both sides of the equation.

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