Problem 16 - Chemistry: The Central Science

Question

Write balanced chemical equations to correspond to each of the following descriptions: (a) When sulfur trioxide gas reacts with water, a solution of sulfuric acid forms. b) Boron sulfide, \(\mathrm{B}_{2} \mathrm{~S}_{3}(s)\), reacts violently with water to form dissolved boric acid, \(\mathrm{H}_{3} \mathrm{BO}_{3}\), and hydrogen sulfide gas. (c) Phosphine, \(\mathrm{PH}_{3}(g)\), combusts in oxygen gas to form water vapor and solid tetraphosphorus decaoxide. (d) When solid mercury(II) nitrate is heated, it decomposes to form solid mercury(II) oxide, gaseous nitrogen dioxide, and oxygen. (e) Copper metal reacts with hot concentrated sulfuric acid solution to form aqueous copper(II) sulfate, sulfur dioxide gas, and water.

Step-by-Step Solution

Answer

The balanced chemical equations are as follows: (a) SO₃(g) + H₂O(l) → H₂SO₄(aq) (b) B₂S₃(s) + 6H₂O(l) → 2H₃BO₃(aq) + 3H₂S(g) (c) 4PH₃(g) + 5O₂(g) → 6H₂O(g) + P₄O₁₀(s) (d) 2Hg(NO₃)₂(s) → 2HgO(s) + 4NO₂(g) + O₂(g) (e) Cu(s) + H₂SO₄(aq) → CuSO₄(aq) + SO₂(g) + H₂O(l)

Step 1: Identify reactants and products, and write their chemical formulas

Reactants: Sulfur trioxide (SO₃), water (H₂O) Product: Sulfuric acid (H₂SO₄)

Step 2: Write the unbalanced chemical equation

SO₃(g) + H₂O(l) → H₂SO₄(aq)

Step 3: Balance the equation

SO₃(g) + H₂O(l) → H₂SO₄(aq) (Already balanced) (b) Boron sulfide, B₂S₃(s), reacts violently with water to form dissolved boric acid, H₃BO₃, and hydrogen sulfide gas.

Step 1: Identify reactants and products, and write their chemical formulas

Reactants: Boron sulfide (B₂S₃), water (H₂O) Products: Boric acid (H₃BO₃), hydrogen sulfide (H₂S)

Step 2: Write the unbalanced chemical equation

B₂S₃(s) + H₂O(l) → H₃BO₃(aq) + H₂S(g)

Step 3: Balance the equation

B₂S₃(s) + 6H₂O(l) → 2H₃BO₃(aq) + 3H₂S(g) (c) Phosphine, PH₃(g), combusts in oxygen gas to form water vapor and solid tetraphosphorus decaoxide.

Step 1: Identify reactants and products, and write their chemical formulas

Reactants: Phosphine (PH₃), oxygen (O₂) Products: Water vapor (H₂O), tetraphosphorus decaoxide (P₄O₁₀)

Step 2: Write the unbalanced chemical equation

PH₃(g) + O₂(g) → H₂O(g) + P₄O₁₀(s)

Step 3: Balance the equation

4PH₃(g) + 5O₂(g) → 6H₂O(g) + P₄O₁₀(s) (d) When solid mercury(II) nitrate is heated, it decomposes to form solid mercury(II) oxide, gaseous nitrogen dioxide, and oxygen.

Step 1: Identify reactants and products, and write their chemical formulas

Reactant: Mercury(II) nitrate (Hg(NO₃)₂) Products: Mercury(II) oxide (HgO), nitrogen dioxide (NO₂), oxygen (O₂)

Step 2: Write the unbalanced chemical equation

Hg(NO₃)₂(s) → HgO(s) + NO₂(g) + O₂(g)

Step 3: Balance the equation

2Hg(NO₃)₂(s) → 2HgO(s) + 4NO₂(g) + O₂(g) (e) Copper metal reacts with hot concentrated sulfuric acid solution to form aqueous copper(II) sulfate, sulfur dioxide gas, and water.

Step 1: Identify reactants and products, and write their chemical formulas

Reactants: Copper (Cu), sulfuric acid (H₂SO₄) Products: Copper(II) sulfate (CuSO₄), sulfur dioxide (SO₂), water (H₂O)

Step 2: Write the unbalanced chemical equation

Cu(s) + H₂SO₄(aq) → CuSO₄(aq) + SO₂(g) + H₂O(l)

Step 3: Balance the equation

Cu(s) + H₂SO₄(aq) → CuSO₄(aq) + SO₂(g) + H₂O(l) (Already balanced)

Key Concepts

Chemical Reactions

Chemical reactions are processes where substances, called reactants, change into new substances, known as products. This transformation occurs due to the rearrangement of atoms, creating a new set of chemical bonds in the products.
In the world of chemistry, these reactions are represented using chemical equations, which show the essential details of the reactants converting into products. Observing these transformations allows us to understand how substances interact and how new compounds form.
For instance, when sulfur trioxide reacts with water to form sulfuric acid, a chemical reaction occurs. Reactants on the left side of the chemical equation, like sulfur trioxide (\( ext{SO}_3(g) \)) and water (\( ext{H}_2 ext{O}(l) \)), come together to produce a new compound, such as sulfuric acid (\( ext{H}_2 ext{SO}_4(aq) \)) which is found on the right side.

Balancing Equations

Balancing chemical equations is crucial because it reflects the conservation of mass principle. This principle ensures that atoms are neither created nor destroyed in a chemical reaction. Consequently, the number of atoms of each element must be the same on both sides of the equation.
Balancing begins with writing the correct unbalanced equation using chemical formulas, outlining what happens during the reaction.
Here's an example: Boron sulfide (\( ext{B}_2 ext{S}_3(s) \)) reacts with water (\( ext{H}_2 ext{O}(l) \)) to form boric acid (\( ext{H}_3 ext{BO}_3(aq) \)) and hydrogen sulfide (\( ext{H}_2 ext{S}(g) \)). To balance the equation, coefficients are used:

1. Determine the initial amounts of each element on both sides.
2. Adjust the coefficients to equalize the number of each type of atom in the reactants and products.
3. Check your work to ensure the equation is balanced.

Thus, the balanced equation becomes (\[ ext{B}_2 ext{S}_3(s) + 6 ext{H}_2 ext{O}(l) \rightarrow 2 ext{H}_3 ext{BO}_3(aq) + 3 ext{H}_2 ext{S}(g) \]).

Reactants and Products

In any chemical equation, reactants and products are fundamental components. Reactants are the starting substances that undergo a chemical change.
Products are the new substances formed as a result of the reaction. The transformation from reactants to products is what defines a chemical reaction.
Understanding the nature and composition of these chemicals is essential. The chemical equations are like recipes that tell us what's needed and what's produced. For example, in this exercise:

• Reactants, such as phosphine (\( ext{PH}_3(g) \)) and oxygen (\( ext{O}_2(g) \)), start the reaction.
• Products, like water vapor (\( ext{H}_2 ext{O}(g) \)) and tetraphosphorus decaoxide (\( ext{P}_4 ext{O}_{10}(s) \)), are the outcome of the chemical process.

Accurate identification of reactants and products is crucial for crafting correct and balanced chemical equations.