Problem 69 - Chemistry: The Central Science

Question

Write a balanced equation for the reaction that occurs in each of the following cases: (a) Potassium metal is exposed to an atmosphere of chlorine gas. (b) Strontium oxide is added to water. (c) A fresh surface of lithium metal is exposed to oxygen gas. (d) Sodium metal reacts with molten sulfur.

Step-by-Step Solution

Answer

(a) \(2K + Cl_2 \rightarrow 2KCl\) (b) \(SrO + H_2O \rightarrow Sr(OH)_2\) (c) \(4Li + O_2 \rightarrow 2Li_2O\) (d) \(2Na + S \rightarrow Na_2S\)

Step 1: (a) Potassium metal is exposed to an atmosphere of chlorine gas.

In this case, the reactants are potassium metal (K) and chlorine gas (Cl₂). When a metal reacts with a non-metal, they will form an ionic compound. Potassium will lose one electron and form a positive ion (K⁺), while chlorine will gain one electron and form a negative ion (Cl⁻). The resulting product is potassium chloride (KCl). Now we can write the balanced equation: \[2K + Cl_2 \rightarrow 2KCl\]

Step 2: (b) Strontium oxide is added to water.

In this reaction, the reactants are strontium oxide (SrO) and water (H₂O). When strontium oxide reacts with water, it forms strontium hydroxide (Sr(OH)₂). The balanced equation for this reaction is: \[SrO + H_2O \rightarrow Sr(OH)_2\]

Step 3: (c) A fresh surface of lithium metal is exposed to oxygen gas.

Here, the reactants are lithium metal (Li) and oxygen gas (O₂). When lithium reacts with oxygen, it forms lithium oxide (Li₂O). The balanced equation for this reaction is: \[4Li + O_2 \rightarrow 2Li_2O\]

Step 4: (d) Sodium metal reacts with molten sulfur.

In this case, the reactants are sodium metal (Na) and sulfur (S). When sodium reacts with sulfur, it forms sodium sulfide (Na₂S). The balanced equation for this reaction is: \[2Na + S \rightarrow Na_2S\] Overall, the balanced equations for the given reactions are as follows: (a) \(2K + Cl_2 \rightarrow 2KCl\) (b) \(SrO + H_2O \rightarrow Sr(OH)_2\) (c) \(4Li + O_2 \rightarrow 2Li_2O\) (d) \(2Na + S \rightarrow Na_2S\)