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.

Short answer

(a) \( SO_3 (g) + H_2 O (l) \rightarrow H_2 SO_4 (aq) \) (b) \( B_2 S_3 (s) + 6 H_2 O (l) \rightarrow 2 H_3 BO_3 (aq) + 3 H_2 S (g) \) (c) \( 4 PH_3 (g) + 8 O_2 (g) \rightarrow 6 H_2 O (g) + P_4 O_{10} (s) \) (d) \( 2 Hg(NO_3)_2 (s) \rightarrow 2 HgO (s) + 4 NO_2 (g) + O_2 (g) \) (e) \( Cu (s) + 2 H_2 SO_4 (aq) \rightarrow CuSO_4 (aq) + 2 SO_2 (g) + 2 H_2 O (l) \)

Step-by-step solution

(a) Sulfur trioxide gas reacts with water to form sulfuric acid

For this reaction, we can identify the reactants and products as follows: Reactants: Sulfur trioxide (SO₃) and water (H₂O) Product: Sulfuric acid (H₂SO₄) Now, let's write the balanced chemical equation: \[ SO_3 (g) + H_2 O (l) \rightarrow H_2 SO_4 (aq) \]

(b) Boron sulfide reacts with water to form boric acid and hydrogen sulfide

For this reaction, we can identify the reactants and products as follows: Reactants: Boron sulfide (B₂S₃) and water (H₂O) Products: Boric acid (H₃BO₃) and hydrogen sulfide (H₂S) Now, let's write the balanced chemical equation: \[ B_2 S_3 (s) + 6 H_2 O (l) \rightarrow 2 H_3 BO_3 (aq) + 3 H_2 S (g) \]

(c) Phosphine combusts in oxygen gas to form water vapor and tetraphosphorus decaoxide

For this reaction, we can identify the reactants and products as follows: Reactants: Phosphine (PH₃) and oxygen (O₂) Products: Water vapor (H₂O) and tetraphosphorus decaoxide (P₄O₁₀) Now, let's write the balanced chemical equation: \[ 4 PH_3 (g) + 8 O_2 (g) \rightarrow 6 H_2 O (g) + P_4 O_{10} (s) \]

(d) Decomposition of solid mercury(II) nitrate

For this reaction, we can identify the reactants and products as follows: Reactant: Mercury(II) nitrate (Hg(NO₃)₂) Products: Solid mercury(II) oxide (HgO), gaseous nitrogen dioxide (NO₂), and oxygen (O₂) Now, let's write the balanced chemical equation: \[ 2 Hg(NO_3)_2 (s) \rightarrow 2 HgO (s) + 4 NO_2 (g) + O_2 (g) \]

(e) Copper reacts with hot concentrated sulfuric acid solution

For this reaction, we can identify the reactants and products as follows: Reactants: Copper metal (Cu) and hot concentrated sulfuric acid (H₂SO₄) Products: Aqueous copper(II) sulfate (CuSO₄), sulfur dioxide gas (SO₂), and water (H₂O) Now, let's write the balanced chemical equation: \[ Cu (s) + 2 H_2 SO_4 (aq) \rightarrow CuSO_4 (aq) + 2 SO_2 (g) + 2 H_2 O (l) \]

Key concepts

Chemical Reactions

Chemical reactions are the bread and butter of chemistry; they are the processes in which substances, known as reactants, transform into new products. These transformations happen through the breaking and forming of chemical bonds during which energy is either absorbed or released. For instance, when sulfur trioxide gas reacts with water, the resultant product is sulfuric acid, and this specific type of reaction is known as a synthesis or combination reaction.

When analyzing a chemical reaction, it is essential to know the properties of the reactants and products, like their physical state (solid, liquid, gas, aqueous), which is indicated by the symbols (s), (l), (g), and (aq) respectively. Understanding these concepts helps in predicting how different substances will interact and what safety precautions might be necessary during the reaction process.

Stoichiometry

Stoichiometry plays a pivotal role in chemistry; it's the quantitative relationship between reactants and products in a chemical reaction. Like baking a cake requires a precise amount of ingredients, a chemical reaction needs exact amounts of reactants to yield the intended products without leaving excess. Observing the problem involving boron sulfide and water, stoichiometry guides us to use six water molecules for every boron sulfide unit to form boric acid and hydrogen sulfide.

Stoichiometry extends beyond just balancing molecules; it involves calculations such as moles, volumes, and masses. Applying stoichiometry requires understanding of the mole concept, Avogadro's number, and molar masses. It also necessitates the ability to convert between units to ensure accurate measurements for a reaction to proceed correctly. Notably, stoichiometry is the fundamental basis of reaction yield predictions, chemical analysis, and industrial applications of chemical processes.

Reaction Balancing

Reaction balancing is the act of ensuring the law of conservation of mass is followed in a chemical equation; it demands that the same number of each type of atom exists on both the reactants' side and the products' side. For example, when copper reacts with sulfuric acid, balancing the reaction involves ensuring that copper, sulfur, oxygen, and hydrogen atoms are accounted for and equal on both sides of the equation.

To balance a reaction, one must systematically adjust the coefficients—the numbers placed before the chemical formulas. Through practice, certain strategies can be employed, such as starting with the most complex molecule typically improves efficiency. Additionally, double-checking the balance by counting the atoms of each element can reaffirm the accuracy of the balanced chemical equation. Balancing reactions is a skill that requires patience and practice but is indispensable for understanding chemical reactions.