Question

Balance each of the following chemical equations. a. \(\operatorname{Br}_{2}(l)+\operatorname{KI}(a q) \rightarrow \operatorname{KBr}(a q)+\mathrm{I}_{2}(s)\) b. \(\mathrm{K}_{2} \mathrm{O}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{KOH}(a q)+\mathrm{O}_{2}(g)\) c. \(\operatorname{LiOH}(s)+\mathrm{CO}_{2}(g) \rightarrow \mathrm{Li}_{2} \mathrm{CO}_{3}(s)+\mathrm{H}_{2} \mathrm{O}(g)\) d. \(\mathrm{K}_{2} \mathrm{CO}_{3}(s)+\mathrm{HNO}_{3}(a q) \rightarrow\) \(\mathrm{KNO}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l)+\mathrm{CO}_{2}(g)\) e. \(\operatorname{LiAlH}_{4}(s)+\mathrm{AlCl}_{3}(s) \rightarrow \mathrm{AlH}_{3}(s)+\mathrm{LiCl}(s)\) g. \(\mathrm{Na}_{2} \mathrm{SO}_{4}(s)+\mathrm{C}(s) \rightarrow \mathrm{Na}_{2} \mathrm{S}(s)+\mathrm{CO}_{2}(g)\) h. \(\mathrm{NaCl}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(l) \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(s)+\mathrm{HCl}(g)\)

Short answer

Balanced chemical equations: a. \(2 Br_2(l) + 2 KI(aq) \rightarrow 2 KBr(aq) + 2 I_2(s)\) b. \(K_2O_2(s) + 2 H_2O(l) \rightarrow 2 KOH(aq) + O_2(g)\) c. \(2 LiOH(s) + CO_2(g) \rightarrow Li_2CO_3(s) + H_2O(g)\) d. \(2 K_2CO_3(s) + 2 HNO_3(aq) \rightarrow 2 KNO_3(aq) + H_2O(l) + 2 CO_2(g)\) e. \(2 LiAlH_4(s) + 2 AlCl_3(s) \rightarrow 2 AlH_3(s) + 4 LiCl(s)\) g. \(Na_2SO_4(s) + 2 C(s) \rightarrow Na_2S(s) + 2 CO_2(g)\) h. \(2 NaCl(s) + H_2SO_4(l) \rightarrow Na_2SO_4(s) + 2 HCl(g)\)

Step-by-step solution

Identify the elements in the equation

List the elements present in the equation: Br, K, I

Count the atoms of each element on both sides

Count the number of atoms of each element for the reactants and products side: Reactants: 2 Br, 1 K, 1 I Products: 1 Br, 1 K, 2 I

Balance the equation

Add coefficients to balance the number of atoms of each element: 2 Br₂(l) + 2 KI(aq) → 2 KBr(aq) + 2 I₂(s) #b. K₂O₂(s) + H₂O(l) → KOH(aq) + O₂(g)#

Identify the elements in the equation

List the elements present in the equation: K, O, H

Count the atoms of each element on both sides

Count the number of atoms of each element for the reactants and products side: Reactants: 2 K, 4 O, 2 H Products: 1 K, 2 O, 1 H

Balance the equation

Add coefficients to balance the number of atoms of each element: K₂O₂(s) + 2 H₂O(l) → 2 KOH(aq) + O₂(g) #c. LiOH(s) + CO₂(g) → Li₂CO₃(s) + H₂O(g)#

Identify the elements in the equation

List the elements present in the equation: Li, O, H, C

Count the atoms of each element on both sides

Count the number of atoms of each element for the reactants and products side: Reactants: 1 Li, 2 O, 1 H, 1 C Products: 2 Li, 3 O, 1 H, 1 C

Balance the equation

Add coefficients to balance the number of atoms of each element: 2 LiOH(s) + CO₂(g) → Li₂CO₃(s) + H₂O(g) And so on for the remaining equations.

Key concepts

Chemical Reactions

Chemical reactions are processes where substances (reactants) are transformed into new substances (products). They involve the breaking and forming of chemical bonds, which is essential for the creation of different materials. For example, when bromine and potassium iodide react, there is a reorganization of atoms that results in the formation of potassium bromide and iodine.

• Reactants: The starting substances in a chemical reaction, like Br₂ and KI in the exercise.
• Products: New substances formed by a chemical reaction, such as KBr and I₂.
• Conservation of Mass: In a chemical reaction, the mass of the reactants equals the mass of the products, meaning atoms are neither created nor destroyed but only rearranged.

When studying chemical reactions, it's crucial to understand these concepts, as they help explain how and why reactions occur.

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It allows chemists to predict the amounts of substances consumed and produced. When you perform stoichiometric calculations, you use the balanced chemical equation to understand the ratios in which reactants combine and products form.

• Mole Ratios: Derived from the coefficients in a balanced equation, they indicate the proportions of each substance involved.
• Quantitative Predictions: By knowing the mole ratios, you can calculate how much of a reactant is needed or how much product will be formed.

Stoichiometry involves creating a link between the macro world we observe and the micro world of molecules and atoms. This connection helps ensure that equations are balanced properly and provides insight into the chemical processes and their efficiencies.

Coefficients in Chemical Equations

Coefficients in chemical equations are numbers placed before formulas to ensure the law of conservation of mass is satisfied. They indicate how many units of each substance participate in the reaction, balancing the equation to reflect equal numbers of each type of atom on both sides. For instance, in the example equation for bromine and potassium iodide, the coefficients are used to balance the molecular quantities:

• Importance of Coefficients: They ensure that each type of atom is accounted for. For Br₂ + KI → KBr + I₂, proper coefficients make it 2 Br₂ + 2 KI → 2 KBr + 1 I₂, balancing both sides.
• How to Adjust Coefficients: Begin with the most complex molecule or the element that appears in the least number of compounds. Adjust coefficients iteratively to balance one element at a time.
• Not a Formula Subscript: Coefficients should not be confused with subscripts within chemical formulas, which indicate the number of atoms in a molecule.

In summary, coefficients are crucial for accurately representing chemical reactions, maintaining balance, and predicting outcome amounts.