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Chapter 6: Problem 31

Calcium oxide is sometimes very challenging to store in the chemistry laboratory. This compound reacts with moisture in the air and is converted to calcium hydroxide. If a bottle of calcium oxide is left on the shelf too long, it gradually absorbs moisture from the humidity in the laboratory. Eventually the bottle cracks and spills the calcium hydroxide that has been produced. Write the unbalanced chemical equation for this process.

Short Answer

Expert verified
The unbalanced chemical equation for the reaction between calcium oxide (CaO) and water (H₂O) to form calcium hydroxide (Ca(OH)₂) is: \(CaO + H_2O \rightarrow Ca(OH)_2\)

Step by step solution

01

Write the unbalanced chemical equation

We need to write the unbalanced chemical equation for the reaction between calcium oxide (CaO) and water (H₂O) to form calcium hydroxide (Ca(OH)₂). \(CaO + H_2O \rightarrow Ca(OH)_2\) This is the unbalanced chemical equation for the reaction.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Calcium Oxide
Calcium oxide, commonly known as quicklime, is a widely used chemical compound. It is an inorganic compound represented by the chemical formula \(\text{CaO}\). This white or grayish substance is formed from the decomposition of limestone, which primarily consists of calcium carbonate. Upon heating, calcium carbonate decomposes to produce calcium oxide and carbon dioxide. This process is known as calcination.

The unique property of calcium oxide is its highly reactive nature, especially when exposed to water or moisture in the air. This reactivity is why calcium oxide is often used in industrial applications, such as cement production, environmental treatments, and chemical synthesis. However, it also poses challenges for storage due to its tendency to react and transform into other compounds.
Chemical Equation
A chemical equation is a symbolic representation of a chemical reaction. It provides important information about the reactants that enter the reaction and the products that are formed. For the reaction between calcium oxide and water, the following unbalanced chemical equation is written: \(\text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2\)

This equation shows that calcium oxide (CaO) reacts with water (H₂O) to produce calcium hydroxide (Ca(OH)₂).

In chemical equations, it is crucial to balance the equation to ensure the law of conservation of mass is respected—that is, the number of atoms of each element is the same on both sides of the equation. In this case, the equation is simple and straightforward, so it is already balanced with equal numbers of calcium, oxygen, and hydrogen on both sides.
Calcium Hydroxide
Calcium hydroxide is an inorganic compound with the chemical formula \(\text{Ca(OH)}_2\), commonly known as slaked lime. This compound forms as a result of the reaction between calcium oxide and water.

Calcium hydroxide is a white powdery substance that has numerous applications. It is used in water and sewage treatment, agriculture to neutralize acidic soils, and in the food industry for processing certain foods.
  • Its ability to act as a strong base makes it useful in pH regulation.
  • It's not only a staple for many industrial processes but also an essential ingredient in lime mortar and plaster.


Handling calcium hydroxide requires care as it can be quite caustic and may cause skin irritation.
Moisture Reaction
The moisture reaction involving calcium oxide is a classic example of a chemical process triggered by environmental conditions. When calcium oxide comes into contact with moisture from the atmosphere, it undergoes a transformation.

The essence of this reaction is the absorption of water, where one molecule of water reacts with calcium oxide to yield calcium hydroxide: \(\text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2\)

Such reactions are considered exothermic, releasing heat as the new chemical bonds form in calcium hydroxide. This moisture reaction is why calcium oxide needs to be stored in airtight containers to prevent it from reacting with ambient moisture.
  • If left exposed, it can lead to the gradual transformation into calcium hydroxide, which is not suitable for certain applications dependent on pure calcium oxide.
  • Additionally, storage vessels may be compromised by repeated moisture reactions, which can eventually lead to cracking and spilling of the content.

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Most popular questions from this chapter

When elemental phosphorus, \(\mathrm{P}_{4},\) burns in oxygen gas, it produces an intensely bright light, a great deal of heat, and massive clouds of white solid phosphorus(V) oxide \(\left(\mathrm{P}_{2} \mathrm{O}_{5}\right)\) product. Given these properties, it is not surprising that phosphorus has been used to manufacture incendiary bombs for warfare. Write the unbalanced equation for the reaction of phosphorus with oxygen gas to produce phosphorus(V) oxide.

What does "balancing" an equation accomplish?

Iron oxide ores, commonly a mixture of \(\mathrm{FeO}\) and \(\mathrm{Fe}_{2} \mathrm{O}_{3}\), are given the general formula \(\mathrm{Fe}_{3} \mathrm{O}_{4}\). They yield elemental iron when heated to a very high temperature with either carbon monoxide or elemental hydrogen. Balance the following equations for these processes. $$\begin{aligned}\mathrm{Fe}_{3} \mathrm{O}_{4}(s)+\mathrm{H}_{2}(g) & \rightarrow \mathrm{Fe}(s)+\mathrm{H}_{2} \mathrm{O}(g) \\ \mathrm{Fe}_{3} \mathrm{O}_{4}(s)+\mathrm{CO}(g) & \rightarrow \mathrm{Fe}(s)+\mathrm{CO}_{2}(g)\end{aligned}$$

Liquid hydrazine, \(\mathrm{N}_{2} \mathrm{H}_{4}\), has been used as a fuel for rockets. When the rocket is to be launched, a catalyst causes the liquid hydrazine to decompose quickly into elemental nitrogen and hydrogen gases. The rapid expansion of the product gases and the heat released by the reaction provide the thrust for the rocket. Write the unbalanced equation for the reaction of hydrazine to produce nitrogen and hydrogen gases.

Balance each of the following chemical equations. a. \(\mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+\mathrm{CaCl}_{2}(a q) \rightarrow \mathrm{CaSO}_{4}(s)+\mathrm{NaCl}(a q)\) b. \(\mathrm{Fe}(s)+\mathrm{H}_{2} \mathrm{O}(g) \rightarrow \mathrm{Fe}_{3} \mathrm{O}_{4}(s)+\mathrm{H}_{2}(g)\) c. \(\mathrm{Ca}(\mathrm{OH})_{2}(a q)+\mathrm{HCl}(a q) \rightarrow \mathrm{CaCl}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l)\) d. \(\operatorname{Br}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l)+\mathrm{SO}_{2}(g) \rightarrow \mathrm{HBr}(a q)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q)\) e. \(\mathrm{NaOH}(s)+\mathrm{H}_{3} \mathrm{PO}_{4}(a q) \rightarrow \mathrm{Na}_{3} \mathrm{PO}_{4}(a q)+\mathrm{H}_{2} \mathrm{O}(l)\) f. \(\operatorname{NaNO}_{3}(s) \rightarrow \operatorname{NaNO}_{2}(s)+\mathrm{O}_{2}(g)\) g. \(\mathrm{Na}_{2} \mathrm{O}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{NaOH}(a q)+\mathrm{O}_{2}(g)\) h \(\mathrm{i}(s)+\mathrm{S}_{8}(s) \rightarrow \mathrm{Si}_{2} \mathrm{~S}_{4}(s)\)
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