Question

Which one of the following is correctly represented? (1) \(\mathrm{Fe}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{Fe}_{2} \mathrm{O}_{3}+\mathrm{H}_{2}\) (2) \(3 \mathrm{Fe}+4 \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{Fe}_{3} \mathrm{O}_{4}+4 \mathrm{H}_{2}\) (3) \(3 \mathrm{Fe}+4 \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{Fe}_{3} \mathrm{O}_{4}(\mathrm{~s})+4 \mathrm{H}_{2}(\mathrm{~g})\) (4) \(3 \mathrm{Fe}(\mathrm{s})+4 \mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \longrightarrow \mathrm{Fe}_{3} \mathrm{O}_{4}(\mathrm{~s})+4 \mathrm{H}_{2}(\mathrm{~g})\)

Short answer

Option (4) is correctly represented.

Step-by-step solution

Identify the Balanced Equation

All chemical equations should be balanced, meaning the number of atoms for each element on the reactants side must equal the number of atoms on the products side. Analyze options to see which one has balanced atoms.

Verify State Symbols

Check whether the given state symbols (s, l, g) match the typical states of the substances at the conditions mentioned.

Evaluate Each Option

Evaluate each option to see if it is balanced and state symbols are appropriately matched.Option (1): Fe + H2O → Fe2O3 + H2 (Not balanced)Option (2): 3 Fe + 4 H2O → Fe3O4 + 4 H2 (Balanced but no state symbols)Option (3): 3 Fe + 4 H2O → Fe3O4(s) + 4 H2(g) (Balanced but no state symbols for Fe and H2O)Option (4): 3 Fe(s) + 4 H2O(g) → Fe3O4(s) + 4 H2(g) (Balanced with proper state symbols)

Key concepts

Chemical Reactions

In chemistry, a chemical reaction is a process where substances, called reactants, transform into new substances known as products. During a reaction, bonds between atoms are broken and new bonds are formed. This gives rise to different substances with unique properties.
It's important to represent chemical reactions accurately using chemical equations. These equations depict the reactants and products, highlighting the transformation that occurs. For example, in the chemical equation \(\text{C}+\text{O}_2 \rightarrow \text{CO}_2\), carbon and oxygen react to form carbon dioxide.
Each element involved must maintain its atom count; no atoms are lost or gained. This conservation is key to understanding the principle of conservation of mass.

State Symbols

State symbols are shorthand notations that describe the physical states of substances in chemical equations. They provide important information about the conditions under which a reaction occurs.

• (s) stands for a solid
• (l) for a liquid
• (g) for a gas
• (aq) indicates an aqueous solution, where a substance is dissolved in water.

Including these symbols in a chemical equation makes the description more complete and accurate. For instance, in the equation \(\text{NaCl}(s) + \text{H}_2\text{O}(l) \rightarrow \text{NaCl}(aq) \), we know that solid salt is added to liquid water to form a saltwater solution.
State symbols help predict the behavior of substances and understand the reaction's context. They are particularly useful in laboratory settings and theoretical analysis.

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions. It is based on the law of conservation of mass, which states that matter cannot be created or destroyed.
In stoichiometry, we use mole ratios derived from balanced chemical equations to calculate the amounts of substances needed or produced. For example, in the balanced equation \(3 \text{H}_2 + \text{N}_2 \rightarrow 2 \text{NH}_3\), the coefficients indicate that 3 moles of hydrogen react with 1 mole of nitrogen to produce 2 moles of ammonia.
Stoichiometry allows chemists to scale reactions up or down, predict yields, and optimize the use of reactants. It is essential for industrial applications, laboratory experiments, and academic studies.

Reaction Balancing

Balancing chemical equations is crucial for accurately describing chemical reactions. This process ensures that the number of atoms for each element is the same on both the reactants and products sides of the equation.
To balance an equation, follow these steps:

• Write down the unbalanced equation.
• Count the number of atoms for each element on both sides.
• Add coefficients to balance the atoms, starting with the most complex molecule.
• Adjust coefficients as needed to balance all elements.
• Double-check to ensure the equation is balanced.

For example, consider the unbalanced equation \( \text{Fe} + \text{O}_2 \rightarrow \text{Fe}_2\text{O}_3 \). Balancing it involves ensuring there are equal numbers of Fe and O atoms on both sides: \3 \text{Fe} + 4 \text{H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4 + 4 \text{H}_2\.
Properly balanced equations are fundamental for understanding reaction stoichiometry and predicting the outcomes of reactions.