Problem 74 - Chemistry Central Science

Question

Write a balanced equation for the reaction that occurs in each of the following cases: (a) Cesium is added to water. (b) Stontium is added to water. (c) Sodium reacts with oxygen. (d) Calcium reacts with iodine.

Step-by-Step Solution

Answer

(a) \( 2 Cs + 2 H₂O \rightarrow 2 CsOH + H₂ \) (b) \( Sr + 2 H₂O \rightarrow Sr(OH)₂ + H₂ \) (c) \( 4 Na + O₂ \rightarrow 2 Na₂O \) (d) \( Ca + I₂ \rightarrow CaI₂ \)

Step 1: (a) Cesium reacts with water.

First, we need to identify the reactants and products of the reaction as follows: - Reactants: Cesium (Cs) and water (H₂O) - Products: Cesium hydroxide (CsOH) and hydrogen gas (H₂) Now, we can write the unbalanced equation: \( Cs + H₂O \rightarrow CsOH + H₂ \) To balance this equation, we need to adjust the coefficients: \( 2 Cs + 2 H₂O \rightarrow 2 CsOH + H₂ \) So, the balanced equation for this reaction is: \( 2 Cs + 2 H₂O \rightarrow 2 CsOH + H₂ \)

Step 2: (b) Strontium reacts with water.

First, we need to identify the reactants and products of the reaction: - Reactants: Strontium (Sr) and water (H₂O) - Products: Strontium hydroxide (Sr(OH)₂) and hydrogen gas (H₂) Now, we can write the unbalanced equation: \( Sr + H₂O \rightarrow Sr(OH)₂ + H₂ \) To balance this equation, we need to adjust the coefficients: \( Sr + 2 H₂O \rightarrow Sr(OH)₂ + H₂ \) So, the balanced equation for this reaction is: \( Sr + 2 H₂O \rightarrow Sr(OH)₂ + H₂ \)

Step 3: (c) Sodium reacts with oxygen.

First, we need to identify the reactants and products of the reaction: - Reactants: Sodium (Na) and oxygen (O₂) - Products: Sodium oxide (Na₂O) Now, we can write the unbalanced equation: \( Na + O₂ \rightarrow Na₂O \) To balance this equation, we need to adjust the coefficients: \( 4 Na + O₂ \rightarrow 2 Na₂O \) So, the balanced equation for this reaction is: \( 4 Na + O₂ \rightarrow 2 Na₂O \)

Step 4: (d) Calcium reacts with iodine.

First, we need to identify the reactants and products of the reaction: - Reactants: Calcium (Ca) and iodine (I₂) - Products: Calcium iodide (CaI₂) Now, we can write the unbalanced equation: \( Ca + I₂ \rightarrow CaI₂ \) To balance this equation, there is no need to adjust the coefficients, since it is already balanced. So, the balanced equation for this reaction is: \( Ca + I₂ \rightarrow CaI₂ \)

Key Concepts

Reaction with Water

When metals react with water, an interesting transformation takes place. This is typically characterized by the formation of hydroxides and the release of hydrogen gas. Let's look at cesium and strontium as examples.

• Cesium and Water: When cesium is added to water, cesium hydroxide (CaOH) is produced, and hydrogen gas is released. The balanced reaction is: \[2Cs + 2H_2O \rightarrow 2CsOH + H_2\]
• Strontium and Water: Strontium undergoes a similar reaction. It forms strontium hydroxide (Sr(OH)₂) and hydrogen gas: \[ Sr + 2H_2O \rightarrow Sr(OH)_2 + H_2\]

These reactions highlight how active metals typically displace the hydrogen in water, forming hydroxides and releasing hydrogen gas.

Reaction with Oxygen

When metals react with oxygen, they form metal oxides. Sodium, for instance, contributes to forming this type of compound.

• Sodium and Oxygen: Sodium reacts vigorously with oxygen to produce sodium oxide. The reaction can be represented and balanced as: \[4Na + O_2 \rightarrow 2Na_2O\]

This process illustrates how various metals create different kinds of oxides depending on their reactivity with oxygen. Understanding the ability of a metal to react with oxygen can offer insights into its basic chemical behavior.

Chemical Reactions

Chemical reactions occur when substances (reactants) interact to form new substances (products). These interactions involve the breaking and forming of bonds, which can significantly change the properties of the materials involved. For example:

• Cesium and Water: A violent reaction yielding cesium hydroxide and hydrogen gas.
• Sodium and Oxygen: Formation of sodium oxide through powerful oxidation.

In these reactions, new compounds with distinct properties from the initial elements are formed, demonstrating the transformative power of chemical reactions.

Chemical Equations

Chemical equations are symbolic representations of a chemical reaction. They display the reactants and products with their respective amounts, represented by coefficients, for balance. Let's analyze:

• Balancing Equations: This essential part involves adjusting coefficients to ensure the same number of each type of atom on both sides of the equation. For instance, with sodium and oxygen:\[4Na + O_2 \rightarrow 2Na_2O\]
• Significance: Balanced equations reflect the law of conservation of mass, meaning matter cannot be created or destroyed. Thus, both sides of the equation must have equal atom counts.

Balanced chemical equations are important tools for understanding the quantitative aspects of a chemical reaction. They help predict the quantities of reactants required or products formed during a reaction.