Problem 12 - General Chemistry: Principles and Modern Applications

Question

By means of a chemical equation, give an example to represent the reaction of (a) a transition metal with a nonoxidizing acid; (b) a transition metal oxide with \(\mathrm{NaOH}(\mathrm{aq}) ;(\mathrm{c})\) an inner transition metal with \(\mathrm{HCl}(\mathrm{aq})\).

Step-by-Step Solution

Answer

The chemical equations are: (a) \(Fe(s) + H_2SO_4(aq) \rightarrow FeSO_4(aq) + H_2(g)\), (b) \(Fe_2O_3(s) + 6NaOH(aq) \rightarrow 2Na_3[Fe(OH)_6](aq)\), and (c) \(La(s) + 2HCl(aq) \rightarrow LaCl_2(aq) + H_2(g)\).

Step 1: Transition metal with a nonoxidizing acid

(a) When a transition metal, say iron (\(Fe\)), reacts with a nonoxidizing acid like sulfuric acid (\(H_2SO_4\)), it forms a corresponding salt and hydrogen gas. The balanced chemical equation for this is: \[Fe(s) + H_2SO_4(aq) \rightarrow FeSO_4(aq) + H_2(g)\]

Step 2: Transition metal oxide with NaOH

(b) A transition metal oxide, such as iron(III) oxide (\(Fe_2O_3\)), reacts with sodium hydroxide (\(NaOH\)) to produce a complex salt and water. The balanced chemical equation for this reaction is: \[Fe_2O_3(s) + 6NaOH(aq) \rightarrow 2Na_3[Fe(OH)_6](aq)\]

Step 3: Inner transition metal with HCl

(c) When an inner transition metal like lanthanum (\(La\)) reacts with hydrochloric acid (\(HCl\)), it forms a corresponding salt and hydrogen gas. The balanced chemical equation for this reaction is: \[La(s) + 2HCl(aq) \rightarrow LaCl_2(aq) + H_2(g)\]

Key Concepts

Transition Metals

Transition metals are fascinating elements found in the middle section of the periodic table. They include metals like iron (Fe), copper (Cu), and gold (Au). Unlike metals from other groups, transition metals can exhibit multiple oxidation states. This means they can lose different numbers of electrons when they form compounds.

Here are some key features of transition metals:

• They are generally good conductors of electricity due to their density and closely packed structure.
• They often form colored compounds, making them useful for various applications like dyes and paints.
• Transition metals can form complex ions by coordinating with other atoms or molecules.
• These metals have high melting and boiling points and are typically hard and strong.

In reactions, transition metals can react with nonoxidizing acids such as sulfuric acid (\(H_2SO_4\)). For example, iron (Fe) reacts with \(H_2SO_4\) to form iron sulfate \(FeSO_4\) and hydrogen gas \(H_2\). This highlights their ability to form salts and release gases, illustrating their diverse reactivity.

Nonoxidizing Acids

Nonoxidizing acids are a category of acids that do not gain oxygen during a reaction. This means that they don’t increase the oxidation state of other substances they react with. Common examples include hydrochloric acid (\(HCl\)) and sulfuric acid (\(H_2SO_4\)) in certain concentrations.

Here are some basic characteristics of nonoxidizing acids:

• They are typically strong acids, readily donating protons \((H^+)\) to other substances.
• They can react with metals to form salts and gases such as hydrogen \(H_2\).
• These acids are often used to clean metals, as they remove rust and scale without causing oxidation.

In the chemical equation \(Fe(s) + H_2SO_4(aq) \rightarrow FeSO_4(aq) + H_2(g)\), sulfuric acid acts as a nonoxidizing acid. It effectively converts iron into iron sulfate while liberating hydrogen gas without oxidizing the iron further.

Inner Transition Metals

Inner transition metals, known as the lanthanides and actinides, reside at the bottom of the periodic table. They include elements like lanthanum (La) and actinium (Ac) and are known for their unique properties and roles in modern technology.

Key features of inner transition metals include:

• They have partially filled f orbitals, which contribute to their complex electronic configurations.
• Many of these metals are prone to oxidation and can form various oxidation states.
• They are often used in high-tech devices, magnets, and as catalysts in chemical reactions.

When an inner transition metal such as lanthanum reacts with hydrochloric acid \((HCl)\), it forms lanthanum chloride \((LaCl_2)\) and hydrogen gas \(H_2\). This reaction exemplifies the ability of inner transition metals to form salts and release hydrogen, similar to other metal-acid reactions.