Question

Predict the products of the following reactions: (a) ${\mathrm{BCl}}_3(\mathrm{g})+{\mathrm{NH}}_3(\mathrm{g})$ (b) $\mathrm{K}(\mathrm{s})+{\mathrm{O}}_2(\mathrm{g})$ (c) $\mathrm{Li}(\mathrm{s})+{\mathrm{O}}_2(\mathrm{g})$ (d) ${\mathrm{BaO}}_2(\mathrm{s})+{\mathrm{H}}_2\mathrm{O}(1)$

Short answer

a) $\mathrm{BN}(\mathrm{s})+3\mathrm{HCl}(\mathrm{g})$, b) $2{\mathrm{K}}_2\mathrm{O}(\mathrm{s})$, c) $2{\mathrm{Li}}_2\mathrm{O}(\mathrm{s})$, d) ${\mathrm{Ba}(\mathrm{OH})}_2(\mathrm{aq})+\frac{1}{2}{\mathrm{O}}_2(\mathrm{g})$

Step-by-step solution

Reaction (a) Solution

The chemical reaction between Boron trichloride ${\mathrm{BCl}}_3$ and ammonia ${\mathrm{NH}}_3$ forms boron nitride $\mathrm{BN}$ and hydrogen chloride $\mathrm{HCl}$. The balanced chemical equation is: ${\mathrm{BCl}}_3(\mathrm{g})+3{\mathrm{NH}}_3(\mathrm{g})➝\mathrm{BN}(\mathrm{s})+3\mathrm{HCl}(\mathrm{g})$

Reaction (b) Solution

The reaction between potassium $\mathrm{K}$ and oxygen ${\mathrm{O}}_2$ results in the formation of potassium oxide ${\mathrm{K}}_2\mathrm{O}$. The balanced chemical equation is:$4\mathrm{K}(\mathrm{s})+{\mathrm{O}}_2(\mathrm{g})➝2{\mathrm{K}}_2\mathrm{O}(\mathrm{s})$

Reaction (c) Solution

Lithium $\mathrm{Li}$ reacts with oxygen ${\mathrm{O}}_2$ to form lithium oxide ${\mathrm{Li}}_2\mathrm{O}$. The balanced chemical equation is:$4\mathrm{Li}(\mathrm{s})+{\mathrm{O}}_2(\mathrm{g})➝2{\mathrm{Li}}_2\mathrm{O}(\mathrm{s})$

Reaction (d) Solution

Barium peroxide ${\mathrm{BaO}}_2$ reacts with water ${\mathrm{H}₀}_2$ to form Barium hydroxide ${\mathrm{Ba}(\mathrm{OH})}_2$ and oxygen ${\mathrm{O}}_2$. The balanced chemical equation is:${\mathrm{BaO}}_2(\mathrm{s})+{\mathrm{H}}_2\mathrm{O}(1)➝{\mathrm{Ba}(\mathrm{OH})}_2(\mathrm{aq})+\frac{1}{2}{\mathrm{O}}_2(\mathrm{g})$

Key concepts

Chemical Equations Balancing

Balancing chemical equations is a fundamental skill in chemistry. It's essential for ensuring that the law of conservation of mass is upheld in a chemical reaction, meaning the number of atoms of each element on the reactant side must be equal to the number of atoms of the same element on the product side. For instance, in reaction (a) where ${\mathrm{BCl}}_3(\text{g})+3{\mathrm{NH}}_3(\text{g})\to \mathrm{BN}(\text{s})+3\mathrm{HCl}(\text{g})$, we balance chlorine and nitrogen atoms to ensure there are three chlorine and one nitrogen atom on both sides. Similarly, reactions (b) and (c) require careful accounting for potassium and lithium atoms, respectively. Occasionally, balancing can involve fractions, like in reaction (d) where $\frac{1}{2}{\mathrm{O}}_2$ is used to balance oxygen atoms.

The process includes identifying reactants and products, writing their chemical formulas, and using coefficients to balance the atoms. Simple tips can make this process easier, such as starting with elements that appear in one compound on each side and saving hydrogen and oxygen for last if they appear in multiple compounds.

Reaction Stoichiometry

Reaction stoichiometry is the quantitative relationship between reactants and products in a chemical reaction. For students to grasp this concept, it is essential to understand that stoichiometry involves calculating the amounts of substances that will react and form in a given chemical equation. An excellent exercise to practice stoichiometry involves reactions (b) and (c), where $4\mathrm{K}(\mathrm{s})+{\mathrm{O}}_2(\text{g})\to 2{\mathrm{K}}_2\mathrm{O}(\text{s})$ and $4\mathrm{Li}(\mathrm{s})+{\mathrm{O}}_2(\text{g})\to 2{\mathrm{Li}}_2\mathrm{O}(\text{s})$, respectively.

Understanding molar ratios, or the ratio of moles of one substance to moles of another in a balanced equation, is key to calculating how much product can be made from a given amount of reactant or how much reactant is needed to make a desired amount of product. Students can use this ratio and the mole concept to relate the mass of one substance to the mass of another.

Inorganic Compounds Reactions

Reactions involving inorganic compounds, like the ones presented in the exercise, are diverse and governed by specific rules regarding the reactivity and properties of the elements and compounds involved. Reaction (a) is a classic example of a combination reaction where two inorganic compounds, ${\mathrm{BCl}}_3(\text{g})$ and ${\mathrm{NH}}_3(\text{g})$, come together to form $\mathrm{BN}(\text{s})$ and $\mathrm{HCl}(\text{g})$. Reactions (b) and (c) are synthesis reactions, where a metal reacts with oxygen to produce a metal oxide.

Furthermore, reaction (d) showcases a decomposition reaction where ${\mathrm{BaO}}_2(\text{s})$ decomposes to form ${\mathrm{Ba}(\mathrm{OH})}_2(\text{aq})$ and ${\mathrm{O}}_2(\text{g})$ when water is added. Understanding the types of reactions that inorganic compounds can undergo is crucial for predicting products and balancing equations.

Reactivity of Metals

The reactivity of metals is a key concept for understanding certain types of inorganic compound reactions, particularly when metals react with nonmetals like oxygen. The reactivity series of metals is a list that ranks metals from most reactive to least reactive. For instance, potassium (K) in reaction (b), being highly reactive, readily reacts with oxygen to form ${\mathrm{K}}_2\mathrm{O}$, a metal oxide. Lithium (Li) shown in reaction (c) behaves similarly, although it is slightly less reactive than potassium.

Metal reactivity influences not only the types of chemical reactions that will occur but also the conditions under which they happen, such as temperature and concentration. In practice, knowing the reactivity series helps chemists predict and control the course of the reactions when working with metals and their compounds.