Problem 17 - Chemistry The Central Science

Question

Complete and balance the following equations: (a) \(\mathrm{NaOCH}_{3}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow\) (b) \(\mathrm{CuO}(s)+\mathrm{HNO}_{3}(a q)\) (c) \(\mathrm{WO}_{3}(s)+\mathrm{H}_{2}(g) \stackrel{\Delta}{\longrightarrow}\) (d) \(\mathrm{NH}_{2} \mathrm{OH}(l)+\mathrm{O}_{2}(g)\) (e) \(\mathrm{Al}_{4} \mathrm{C}_{3}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow\)

Step-by-Step Solution

Answer

The balanced chemical equations for the given reactions are: (a) \(\mathrm{NaOCH}_{3}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{NaOH}(aq) + \mathrm{CH}_{3}\mathrm{OH}(l)\) (b) \(\mathrm{CuO}(s) + 2\mathrm{HNO}_{3}(aq) \longrightarrow \mathrm{Cu(NO}_{3})_{2}(aq) + \mathrm{H}_{2}\mathrm{O}(l)\) (c) \(\mathrm{WO}_{3}(s) + 3\mathrm{H}_{2}(g) \stackrel{\Delta}{\longrightarrow} \mathrm{W}(s) + 3 \mathrm{H}_{2}\mathrm{O}(g)\) (d) \(2\mathrm{NH}_{2} \mathrm{OH}(l)+\mathrm{O}_{2}(g) \longrightarrow 3\mathrm{H}_{2}\mathrm{O}(l) + \mathrm{N}_{2}(g)\) (e) \(\mathrm{Al}_{4} \mathrm{C}_{3}(s) + 12\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow 4\mathrm{Al(OH)}_{3}(s) + 3\mathrm{CH}_{4}(g)\)

Step 1: (a) Complete the equation

For equation (a), sodium methoxide (NaOCH3) reacts with water (H2O). The products of this reaction are sodium hydroxide (NaOH) and methanol (CH3OH). So, the completed equation is: \(\mathrm{NaOCH}_{3}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{NaOH}(aq) + \mathrm{CH}_{3}\mathrm{OH}(l)\) Now, we need to balance the equation.

Step 2: (a) Balance the equation

In this case, the equation is already balanced: \[\mathrm{NaOCH}_{3}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{NaOH}(aq) + \mathrm{CH}_{3}\mathrm{OH}(l)\]

Step 3: (b) Complete and balance the equation

For equation (b), copper oxide (CuO) reacts with nitric acid (HNO3). The products of this reaction are copper nitrate (Cu(NO3)2) and water (H2O). The completed equation is: \(\mathrm{CuO}(s) + \mathrm{HNO}_{3}(aq) \longrightarrow \mathrm{Cu(NO}_{3})_{2}(aq) + \mathrm{H}_{2}\mathrm{O}(l)\) Now, balance the equation by adding a 2 in front of HNO3: \[\mathrm{CuO}(s) + 2\mathrm{HNO}_{3}(aq) \longrightarrow \mathrm{Cu(NO}_{3})_{2}(aq) + \mathrm{H}_{2}\mathrm{O}(l)\]

Step 4: (c) Complete and balance the equation

For equation (c), tungsten trioxide (WO3) reacts with hydrogen gas (H2) under heat, producing tungsten (W) and water (H2O). The completed equation is: \(\mathrm{WO}_{3}(s) + \mathrm{H}_{2}(g) \stackrel{\Delta}{\longrightarrow} \mathrm{W}(s) + \mathrm{H}_{2}\mathrm{O}(g)\) Balance the equation by adding a 3 in front of H2O and a 3 in front of H2: \[\mathrm{WO}_{3}(s) + 3\mathrm{H}_{2}(g) \stackrel{\Delta}{\longrightarrow} \mathrm{W}(s) + 3 \mathrm{H}_{2}\mathrm{O}(g)\]

Step 5: (d) Complete and balance the equation

For equation (d), hydroxylamine (NH2OH) reacts with oxygen gas (O2) to produce water (H2O) and nitrogen gas (N2). The completed equation is: \(\mathrm{NH}_{2} \mathrm{OH}(l)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{H}_{2}\mathrm{O}(l) + \mathrm{N}_{2}(g)\) Balance the equation by adding coefficients as follows: \[2\mathrm{NH}_{2} \mathrm{OH}(l)+\mathrm{O}_{2}(g) \longrightarrow 3\mathrm{H}_{2}\mathrm{O}(l) + \mathrm{N}_{2}(g)\]

Step 6: (e) Complete and balance the equation

For equation (e), aluminum carbide (Al4C3) reacts with water (H2O) to produce aluminum hydroxide (Al(OH)3) and methane (CH4). The completed equation is: \(\mathrm{Al}_{4} \mathrm{C}_{3}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{Al(OH)}_{3}(s) + \mathrm{CH}_{4}(g)\) Balance the equation by adding coefficients as follows: \[\mathrm{Al}_{4} \mathrm{C}_{3}(s) + 12\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow 4\mathrm{Al(OH)}_{3}(s) + 3\mathrm{CH}_{4}(g)\]

Key Concepts

Chemical Reactions

Chemical reactions are processes where substances, known as reactants, are transformed into different substances, referred to as products. In the context of the provided exercise, we see a variety of chemical reactions.
These reactions involve substances undergoing chemical changes and rearrangements.

• In equation (a), sodium methoxide reacts with water to form sodium hydroxide and methanol.
• In equation (b), copper oxide reacts with nitric acid to form copper nitrate and water.
• For equation (c), tungsten trioxide, when heated in the presence of hydrogen, is reduced to tungsten metal and water is produced as a by-product.
• Equation (d) represents the oxidation of hydroxylamine with oxygen to yield nitrogen gas and water.
• Lastly, equation (e) illustrates the reaction of aluminum carbide with water, forming aluminum hydroxide and releasing methane gas.

Each of these reactions demonstrates the transformation of the reactants into products through the breaking and forming of bonds, which is the essence of chemical reactions.

Stoichiometry

Stoichiometry is the field of chemistry that focuses on the quantitative relationships within chemical reactions. It's essentially about measuring these relationships and ensuring equations are balanced. This balance is crucial to satisfy the law of conservation of mass, which states that mass in a closed system is constant over time.
For the chemical equations in the exercise, stoichiometry ensures the same number of each type of atom on both sides:

• In equation (b), balancing is necessary to reflect the chemical reality. By ensuring twice as many nitric acid molecules as copper oxide molecules, we accurately portray the need for chemical equilibrium.
• In equation (c), adjusting the coefficients of hydrogen and water emphasizes the regulation of atomic count and molecular structure during reaction.
• Similarly, the stoichiometry of equation (e) authenticates resulting products like methane through correct ratio establishment among aluminum carbide and water molecules.

This process clarifies the quantitative aspects of chemical equations, ensuring that they reflect the actual reaction conditions accurately.

Inorganic Chemistry

Inorganic chemistry is the branch dealing primarily with compounds that are not based on carbon-hydrogen bonds, excluding some simple carbon-containing compounds. Most of the substances in the presented equations are inorganic compounds.

• Sodium methoxide and water in equation (a) are involved in a simple acid-base chemistry reaction to form inorganic products.
• Copper oxide and nitric acid in equation (b) represent typical inorganic redox chemistry, where transfer of electrons leads to the formation of copper nitrate.
• Tungsten trioxide's reduction in equation (c) highlights inorganic chemistry's focus on metallic compounds like tungsten.
• The reaction between aluminum carbide and water in equation (e) represents the formation of an important class of compounds – metal hydroxides.

Studying inorganic reactions like these provides insight into the behavior of metals, minerals, and other non-organic materials in various chemical systems. These reactions are critical in industrial processes, environmental chemistry, and materials science.