Problem 23 - Chemistry in 30 days

Question

In the reaction. \(\mathrm{SnCl}_{2}+\mathrm{HgCl}_{2} \rightarrow \mathrm{A}+\mathrm{SnCl}_{4} ; \mathrm{A}\) is (a) \(\mathrm{H}_{\mathrm{g}_{2}} \mathrm{Cl}_{2}\) (b) \(\overline{\mathrm{Hg}}\) (c) \(\mathrm{HgCl}\) (d) \(\mathrm{HgCl}_{3}\)

Step-by-Step Solution

Answer

\( \mathrm{A} \) is \( \overline{\mathrm{Hg}} \).

Step 1: Identify given chemical reaction

The given chemical reaction is \( \mathrm{SnCl}_2 + \mathrm{HgCl}_2 \rightarrow \mathrm{A} + \mathrm{SnCl}_4 \). In this reaction, \( \mathrm{A} \) needs to be identified.

Step 2: Analyze the oxidation states

Determine the change in oxidation states. Initially, in \( \mathrm{SnCl}_2 \), tin (\( \mathrm{Sn} \)) is in the +2 oxidation state. The formation of \( \mathrm{SnCl}_4 \) shows it changes to a +4 oxidation state, indicating \( \mathrm{Sn} \) is oxidized. Thus, \( \mathrm{Hg} \) must be reduced in \( \mathrm{HgCl}_2 \). In \( \mathrm{HgCl}_2 \), mercury (\( \mathrm{Hg} \)) is in the +2 oxidation state. To offset this, \( \mathrm{Hg} \) will reduce to the elemental state, 0.

Step 3: Determine the identity of A

Since \( \mathrm{HgCl}_2 \) gets reduced and \( \mathrm{SnCl}_4 \) is formed, \( \mathrm{A} \) must be the elemental form of mercury, which is \( \overline{\mathrm{Hg}} \). This is because \( \mathrm{Hg} \) is reduced from a +2 oxidation to 0.

Key Concepts

Oxidation States

An oxidation state is an important concept in chemistry, helping us understand the behavior of atoms during reactions. It denotes the degree of oxidation of an atom, essentially telling us how many electrons an atom has gained or lost.

For example, in the compound \( \mathrm{SnCl}_2 \), tin (\( \mathrm{Sn} \)) is in the +2 oxidation state. This means that it has lost 2 electrons. Conversely, if an atom has a negative oxidation state, it indicates the atom has gained electrons.

When oxidation states change in a chemical reaction, it signifies that a redox reaction is occurring. Redox is shorthand for "reduction-oxidation", referring to the two processes happening simultaneously: oxidation where atoms lose electrons, and reduction where atoms gain electrons.

Chemical Reaction Identification

Identifying a chemical reaction involves determining the reactants, the products, and any changes that take place at the atomic level. This process helps in understanding what each component's role is in the chemical transformation.

In our exercise, the reaction begins with \( \mathrm{SnCl}_2 \) and \( \mathrm{HgCl}_2 \). The goal is to identify what substance \( \mathrm{A} \) becomes after these react.

By analyzing which compounds appear in the reaction and noting that certain oxidation states change, we can deduce that new substances are formed. Specifically, here the tin moves from a +2 oxidation state to a +4 state, indicating a transformation involving oxidation.

Redox Chemistry

Redox chemistry involves reactions where oxidation and reduction occur together. These reactions are fundamental in chemistry as they involve the transfer of electrons between substances.

In the provided example, we observe a redox reaction: tin is oxidized as it goes from \( \mathrm{SnCl}_2 \) to \( \mathrm{SnCl}_4 \), and simultaneously, mercury is reduced from \( \mathrm{HgCl}_2 \) to its elemental form, \( \overline{\mathrm{Hg}} \).

When analyzing redox reactions, notice which substances gain electrons (reduction) and which lose electrons (oxidation). This helps in deciphering complex reactions, often allowing chemists to predict the products formed. Understanding electron transfer is crucial because it dictates how energy changes within the reaction and can influence reaction rates.

In practice, redox reactions are everywhere - from combustion to cellular respiration, showcasing their significance in both natural and industrial processes.