Question

Write equations for the following processes, involved in the extraction of the elements from their ores: (a) the reduction of boron oxide by \(\mathrm{Mg}\) (b) the result of the addition of hot aqueous \(\mathrm{NaOH}\) to a mixture of solid \(\mathrm{Al}_{2} \mathrm{O}_{3}\) and \(\mathrm{Fe}_{2} \mathrm{O}_{3}\) (c) the reaction of \(\mathrm{CO}_{2}\) with aqueous \(\mathrm{Na}\left[\mathrm{Al}(\mathrm{OH})_{4}\right]\)

Short answer

(a) \(\text{B}_2\text{O}_3 + 3\text{Mg} \rightarrow 2\text{B} + 3\text{MgO}\); (b) \(\text{Al}_2\text{O}_3 + 2\text{NaOH} + 3\text{H}_2\text{O} \rightarrow 2\text{NaAl(OH)}_4\); (c) \(2 \text{Na[Al(OH)}_4] + \text{CO}_2 \rightarrow 2 \text{Al(OH)}_3 + \text{Na}_2\text{CO}_3\)."

Step-by-step solution

Identify the reactants and products for each process

For each process, determine the initial reactants and the expected products. (a) Reduction process: Boron oxide (\(\text{B}_2\text{O}_3\)) is reduced by magnesium (\(\text{Mg}\)), forming boron (\(\text{B}\)) and magnesium oxide (\(\text{MgO}\)).(b) Reaction with aqueous \(\text{NaOH}\): A mixture of \(\text{Al}_2\text{O}_3\) and \(\text{Fe}_2\text{O}_3\) is treated with \(\text{NaOH}\), forming sodium aluminate (\(\text{NaAlO}_2\)) and iron (III) oxide, which remains unchanged as it is insoluble.(c) Reaction with \(\text{CO}_2\): Encountering \(\text{Na[Al(OH)}_4]\), \(\text{CO}_2\) produces aluminium hydroxide (\(\text{Al(OH)}_3\)) and sodium carbonate (\(\text{Na}_2\text{CO}_3\)).

Write the balanced chemical equation for process (a)

For the reduction of boron oxide by magnesium:\[ \text{B}_2\text{O}_3 + 3 \text{Mg} \rightarrow 2 \text{B} + 3 \text{MgO} \]

Write the chemical equation for process (b)

For the reaction of \(\text{Al}_2\text{O}_3\) and \(\text{Fe}_2\text{O}_3\) with \(\text{NaOH}\):\[ \text{Al}_2\text{O}_3 + 2 \text{NaOH} + 3 \text{H}_2\text{O} \rightarrow 2 \text{NaAl(OH)}_4 \]The \(\text{Fe}_2\text{O}_3\) does not react and remains as a solid.

Write the chemical equation for process (c)

For the reaction of \(\text{CO}_2\) with \(\text{Na[Al(OH)}_4]\):\[ 2 \text{Na[Al(OH)}_4] + \text{CO}_2 \rightarrow 2 \text{Al(OH)}_3 + \text{Na}_2\text{CO}_3 \]

Final Verification: Confirm balance and correctness

Each reaction is examined to ensure the equations are balanced. Confirm that both reactants and products match the described chemical processes:(a) \(\text{B}_2\text{O}_3\) reduction: checked.(b) \(\text{NaOH}\) reaction: aluminium-related compound change verified, \(\text{Fe}_2\text{O}_3\) remains unchanged.(c) \(\text{CO}_2\) reaction: all compounds and coefficients are accurate in the conversion to \(\text{Na}_2\text{CO}_3\) and \(\text{Al(OH)}_3\).

Key concepts

Chemical Reactions in Metal Extraction

Chemical reactions are fundamental to the extraction of metals from their ores. These reactions allow us to convert naturally occurring compounds into usable metals. During these processes, the bonds in the compounds are broken, and new bonds are formed between different elements, resulting in the desired products.

For instance, the reaction of boron oxide \(\text{B}_2\text{O}_3\) with magnesium \(\text{Mg}\) is a clear demonstration of breaking and forming chemical bonds. In this reaction, boron is extracted from its oxide form by utilizing the chemical properties of magnesium. The magnesium bonds with the oxygen atoms, freeing the boron in the process. This is a prime example of how chemical reactions are harnessed to achieve metal extraction.

Reduction Process

Reduction processes play a key role in metal extraction, particularly when it comes to removing oxygen from metal oxides. In a reduction, an element gains electrons, thereby reducing its oxidation state.

Taking the reduction of boron oxide as an example, we can see this clearly:

• Boron oxide (\(\text{B}_2\text{O}_3\)) is heated with magnesium (\(\text{Mg}\)).
• The magnesium acts as a reducing agent, providing electrons to liberate boron from its oxygen bonds.
• As a result, magnesium forms magnesium oxide (\(\text{MgO}\)), while boron is isolated in its elemental form (\(\text{B}\)).

Understanding reduction is crucial, as it shows the removal of unwanted elements from a compound to isolate the metal. It is one of the fundamental procedures in metallurgy.

Sodium Aluminate Formation

Sodium aluminate is formed through a reaction involving aluminum oxide and sodium hydroxide. This process is a crucial example of metallurgical chemistry in action.

When aluminum oxide (\(\text{Al}_2\text{O}_3\)) is treated with sodium hydroxide (\(\text{NaOH}\)), the components react in the presence of water. The outcome of this reaction is sodium aluminate (\(\text{NaAlO}_2\)):

• The sodium in \(\text{NaOH}\)replaces the oxygen from aluminum oxide.
• Water (\(\text{H}_2\text{O}\)) also plays a role, as it aids in dissolving and facilitating the reaction.

While aluminum forms a soluble compound, iron (III) oxide (\(\text{Fe}_2\text{O}_3\)) does not react and remains as a solid. This selectivity showcases the utility of chemical reactions in selectively processing ores.

Balanced Chemical Equations in Extraction

The ability to write and understand balanced chemical equations is a vital skill in chemistry, particularly in metal extraction processes. Balanced equations accurately reflect the conservation of mass. This means that the number of each type of atom on the reactant side equals the number of those atoms on the product side.

For example, consider the reaction of \(\text{CO}_2\) with an aqueous solution of \(\text{Na[Al(OH)}_4]\). The balanced chemical equation for this reaction is:\[ 2 \text{Na[Al(OH)}_4] + \text{CO}_2 \rightarrow 2 \text{Al(OH)}_3 + \text{Na}_2\text{CO}_3 \]

• Two molecules of sodium aluminate react with one molecule of carbon dioxide.
• The products formed are two molecules of aluminum hydroxide and one molecule of sodium carbonate.

Balancing these equations ensures that you are considering all substances involved in a reaction. It's key to preventing errors in calculation and understanding the stoichiometry of reactions used in metal extraction.