Question

Balance each of the following chemical equations by inspection: (a) \(\mathrm{F}_{2}(g)+\operatorname{NaBr}(a q) \rightarrow \operatorname{Br}_{2}(l)+\operatorname{NaF}(a q)\) (b) \(\mathrm{Sb}_{2} \mathrm{~S}_{3}(\mathrm{~s})+\mathrm{HCl}(a q) \rightarrow \mathrm{SbCl}_{3}(a q)+\mathrm{H}_{2} \mathrm{~S}(g)\)

Short answer

(a) \( \mathrm{F}_{2}(g)+2\mathrm{NaBr}(aq) \rightarrow \mathrm{Br}_{2}(l)+2\mathrm{NaF}(aq) \). (b) \( \mathrm{Sb}_{2}\mathrm{~S}_{3}(s)+6\mathrm{HCl}(aq) \rightarrow 2\mathrm{SbCl}_{3}(aq)+3\mathrm{H}_{2}\mathrm{~S}(g) \).

Step-by-step solution

Identify Atoms in Equation (a)

For equation (a), identify the atoms present: Fluorine (F), Sodium (Na), Bromine (Br). In the equation \( \mathrm{F}_{2}(g)+\operatorname{NaBr}(aq) \rightarrow \operatorname{Br}_{2}(l)+\operatorname{NaF}(aq) \), there are 2 F atoms, 1 Na, and 1 Br on the reactant side, and 2 Br, 2 Na, and 2 F atoms on the product side.

Balance Atom Equation (a)

Start by balancing the number of atoms for each element. First, balance Br by placing a coefficient of 2 in front of \( \mathrm{NaBr} \) to give 2 Br atoms on each side: \( \mathrm{F}_{2}(g)+2\mathrm{NaBr}(aq) \rightarrow \mathrm{Br}_{2}(l)+2\mathrm{NaF}(aq) \). This automatically balances Na and Br as well.

Verify Balance for Equation (a)

Check that each type of atom is balanced: 2 F on both sides, 2 Na on both sides, and 2 Br on both sides. The equation is now balanced: \( \mathrm{F}_{2}(g)+2\operatorname{NaBr}(aq) \rightarrow \operatorname{Br}_{2}(l)+2\operatorname{NaF}(aq) \).

Identify Atoms in Equation (b)

For equation (b), identify the atoms in the reactants and products: Antimony (Sb), Sulfur (S), Hydrogen (H), Chlorine (Cl). In the equation \( \mathrm{Sb}_{2}\mathrm{~S}_{3}(s)+\mathrm{HCl}(aq) \rightarrow \mathrm{SbCl}_{3}(aq)+\mathrm{H}_{2}\mathrm{~S}(g) \), there are 2 Sb, 3 S, 1 Cl, and 1 H on the reactant side.

Balance Atom Equation (b)

Start by balancing S by placing a coefficient of 3 in front of \( \mathrm{H}_{2}\mathrm{~S} \) to balance S. Then balance Cl by placing a coefficient of 6 in front of \( \mathrm{HCl} \), which balances Cl and H: \( \mathrm{Sb}_{2}\mathrm{~S}_{3}(s)+6\mathrm{HCl}(aq) \rightarrow 2\mathrm{SbCl}_{3}(aq)+3\mathrm{H}_{2}\mathrm{~S}(g) \).

Verify Balance for Equation (b)

Check that each type of atom is balanced: 2 Sb, 3 S, 6 Cl, and 6 H are on both sides. The equation is balanced: \( \mathrm{Sb}_{2}\mathrm{~S}_{3}(s)+6\mathrm{HCl}(aq) \rightarrow 2\mathrm{SbCl}_{3}(aq)+3\mathrm{H}_{2}\mathrm{~S}(g) \).

Key concepts

Chemical Reactions

Chemical reactions are processes where substances, known as reactants, are transformed into new substances called products. During a chemical reaction, the atoms in the reactants are rearranged to form products, but the atoms themselves are not created or destroyed. This change happens when chemical bonds between atoms break and new bonds form.
One important aspect of studying chemical reactions is writing them as chemical equations. These equations symbolically represent the reactants and products involved in the reaction. Each element is represented by its chemical symbol, and the substances are shown by their chemical formulas. By properly writing and balancing chemical equations, we get a clear picture of what's occurring during a chemical reaction.
The ability to predict the outcome of a chemical reaction requires understanding the conditions that affect reactions, such as temperature, pressure, and the presence of catalysts. Whether you're observing the fizzing of Alka-Seltzer in water or the rusting of iron, you're witnessing chemical reactions at work.

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It involves calculating the amount of each substance involved in the reaction and ensures the proper proportions are used to achieve a balanced equation.
When balancing chemical equations, stoichiometry is used to determine the correct coefficients that make the number of each type of atom equal on both sides of the equation. By following the principle of stoichiometry, each molecule or compound is represented accurately according to its molar mass, and the equations reflect the conservation of atoms.
For example, in the balanced equation for the reaction of fluorine gas with sodium bromide: \[ ext{F}_2(g) + 2 ext{NaBr}(aq) ightarrow ext{Br}_2(l) + 2 ext{NaF}(aq) \] The coefficient "2" before NaBr and NaF ensures that the number of bromide and sodium atoms is conserved during the reaction. This approach applies universally to chemical equations, allowing chemists to predict the amounts of products produced from a given amount of reactants.

Conservation of Mass

The conservation of mass is a fundamental principle in chemistry stating that mass is neither created nor destroyed in a chemical reaction. This principle was established by Antoine Lavoisier in the 18th century and forms the basis for balancing chemical equations.
In every reaction, the mass of the reactants equals the mass of the products. This principle requires that the same number of each type of atoms be present on both sides of a chemical equation, ensuring that the mass remains constant throughout the reaction.
For example, in the balanced reaction:\[ ext{Sb}_2 ext{S}_3(s) + 6 ext{HCl}(aq) ightarrow 2 ext{SbCl}_3(aq) + 3 ext{H}_2 ext{S}(g) \] The number of Sb, S, H, and Cl atoms remains consistent, ensuring that total mass is conserved. This concept is vital for the accurate measurement and prediction of chemical processes in laboratories and industries worldwide. By adhering to conservation of mass, chemists can track substances through reactions, ensuring safety and efficiency in experiments and manufacturing processes.