Question

Write a balanced chemical equation for each reaction: (a) Calcium metal reacts with solid phosphorus, \(\mathrm{P}_{4}\), to form calcium phosphide. (b) Sodium metal reacts with water to produce aqueous sodium hydroxide and hydrogen gas. (c) Ammonium nitrate powder explodes to form nitrogen gas, oxygen gas, and water vapor.

Short answer

(a) 3Ca + P4 → Ca3P2 (b) 2Na + 2H2O → 2NaOH + H2 (c) 2NH4NO3 → N2 + 3O2 + 4H2O

Step-by-step solution

(a) Calcium metal reacts with solid phosphorus to form calcium phosphide

1. Reactants: Calcium metal (Ca) and solid phosphorus (P4) Product: Calcium phosphide (Ca3P2) 2. Write the unbalanced equation: Ca + P4 → Ca3P2 3. Balance the equation: We need 3 calcium atoms and 2 phosphorus atoms on both sides of the equation. 3Ca + P4 → Ca3P2 The equation is now balanced.

(b) Sodium metal reacts with water to produce aqueous sodium hydroxide and hydrogen gas

1. Reactants: Sodium metal (Na) and water (H2O) Products: Aqueous sodium hydroxide (NaOH) and hydrogen gas (H2) 2. Write the unbalanced equation: Na + H2O → NaOH + H2 3. Balance the equation: We need 2 hydrogen atoms on both sides of the equation. The easiest way to do this is to have 2 moles of Na and NaOH as well as 1 mole of H2O and H2. 2Na + 2H2O → 2NaOH + H2 The equation is now balanced.

(c) Ammonium nitrate powder explodes to form nitrogen gas, oxygen gas, and water vapor

1. Reactant: Ammonium nitrate (NH4NO3) Products: Nitrogen gas (N2), Oxygen gas (O2), and water vapor (H2O) 2. Write the unbalanced equation: NH4NO3 → N2 + O2 + H2O 3. Balance the equation: First, balance the nitrogen atoms: 2NH4NO3 → N2 + O2 + H2O Next, balance the hydrogen atoms: 2NH4NO3 → N2 + O2 + 4H2O Finally, balance the oxygen atoms: 2NH4NO3 → N2 + 3O2 + 4H2O The equation is now balanced.

Key concepts

Chemical Reactions

Chemical reactions are essential processes that transform one set of substances into another. They involve reactants, which are the starting materials, and products, which are the substances formed by the reaction. Chemical reactions occur all around us and are crucial for various natural phenomena and industrial processes.

There are many types of chemical reactions, including:

• Synthesis Reactions: Two or more reactants combine to form a single product. For example, when calcium metal reacts with phosphorus to form calcium phosphide, it is a synthesis reaction.
• Decomposition Reactions: A single compound breaks down into two or more simpler substances. The explosion of ammonium nitrate into nitrogen, oxygen, and water vapor is a decomposition reaction.
• Single Replacement Reactions: An element replaces another element in a compound. For instance, sodium reacting with water to produce sodium hydroxide and hydrogen gas is a single replacement reaction.

Understanding the type of reaction helps predict the possible products and their quantities.

Stoichiometry

Stoichiometry is the area of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. It enables chemists to predict the amount of substances consumed and produced in a reaction, which is fundamental for efficient resource usage in various applications.

To perform stoichiometric calculations, the balanced chemical equation is essential because it shows the ratio in which chemicals react and are produced. This ratio is represented by the coefficients in the balanced equation, which indicate the number of moles of each substance involved.

• For the reaction of sodium with water, the balanced equation: \[2\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2\] tells us that 2 moles of sodium react with 2 moles of water to produce 2 moles of sodium hydroxide and 1 mole of hydrogen gas. This ratio helps calculate the amounts of each substance needed or formed in the reaction.

Accurately using stoichiometry allows scientists and engineers to maximize yields and minimize waste, making processes more sustainable and cost-effective.

Chemical Equation Balancing

Balancing chemical equations is a vital skill for understanding chemical reactions. It ensures the law of conservation of mass holds, meaning matter is not created or destroyed in a chemical reaction. To balance an equation, the number of each type of atom must be equal on both sides of the equation.

Here's a step-by-step method to balance chemical equations:

• Write the unbalanced equation with the correct formulas for each reactant and product.
• Count the number of atoms of each element on both sides of the equation.
• Add coefficients in front of the formulas to balance the number of atoms for each element across the equation.
• Repeat adjusting coefficients until the equation is balanced.

Let's consider how this process works in a practical scenario:- For ammonium nitrate's decomposition: Begin with the unbalanced equation: \[ \text{NH}_4\text{NO}_3 \rightarrow \text{N}_2 + \text{O}_2 + \text{H}_2\text{O} \] After balancing, it becomes: \[ 2\text{NH}_4\text{NO}_3 \rightarrow \text{2N}_2 + \text{3O}_2 + \text{4H}_2\text{O} \] This balanced equation reflects the correct proportions of reactants and products, necessary for accurate stoichiometric calculations. Understanding these principles forms a foundational skill in chemistry, aiding in the analysis and prediction of reaction behavior.