Question

What happens when (i) sodium metal is dropped in water? (ii) sodium metal is heated in free supply of air? (iii) sodium peroxide dissolves in water?

Short answer

(i) Sodium reacts with water to form NaOH and H₂ gas. (ii) Sodium in air forms Na₂O. (iii) Sodium peroxide in water forms NaOH and releases O₂.

Step-by-step solution

Sodium metal in water reaction

When sodium metal (Na) is dropped in water (H₂O), it reacts vigorously. Sodium is an alkali metal and reacts with water to form sodium hydroxide (NaOH) and hydrogen gas (H₂), releasing a lot of heat. The reaction is as follows:$$2Na+2H_{2}O\to 2NaOH+H_2$$ This reaction is exothermic, meaning heat is released, and it can cause the hydrogen gas to ignite.

Sodium metal in air

When sodium metal is heated in a free supply of air, it reacts with oxygen to form sodium oxide (Na₂O). Sodium burns with a bright yellow flame. The reaction is described by the chemical equation:$$4Na+O_2\to 2N{a}_{2}O$$ This reaction shows that sodium combines with oxygen in the air to form a basic oxide.

Dissolving sodium peroxide in water

When sodium peroxide (Na₂O₂) dissolves in water, it forms sodium hydroxide (NaOH) and releases oxygen gas (O₂). The reaction is as follows:$$2N{a}_2{O}_2+2H_{2}O\to 4NaOH+O_2$$ This results in an alkaline solution and the release of oxygen gas.

Key concepts

Exothermic Reaction

An exothermic reaction is a chemical reaction that releases energy in the form of heat or light. When sodium metal is added to water, it causes an exothermic reaction. This means that as the sodium and water combine, they release a significant amount of heat. This particular reaction is so vigorous because sodium is very reactive.
This heat release often makes the hydrogen gas, produced during the reaction, catch fire. That's why we often see flames when sodium is put into water. Here's how the reaction can be represented:

• Sodium (Na) reacts with water (H₂O) to form sodium hydroxide (NaOH) and hydrogen gas (H₂).
• The chemical equation is: $$2Na+2H_{2}O\to 2NaOH+H_2$$
• Notice how hydrogen gas is produced, which can ignite from the heat released.

Understanding exothermic reactions is crucial to predict how chemicals will behave and respond in different environments.

Alkali Metals

Alkali metals are found in group 1 of the periodic table. They include lithium, sodium, potassium, rubidium, cesium, and francium. These elements are known for their high reactivity, especially with water, and are characterized by having one electron in their outermost shell.
Sodium, an alkali metal, is highly reactive due to its desire to lose one electron and form a stable configuration. This characteristic accounts for why sodium reacts so quickly and vigorously with water, producing heat and hydrogen gas.
When sodium reacts with oxygen, it forms sodium oxide. Due to sodium's high reactivity, precautions should be taken when handling it. These reactions are typical for alkali metals:

• They form hydroxides with water.
• They can ignite or explode if not carefully monitored.
• Handling often requires observing safety protocols to prevent accidents.

Sodium Hydroxide

Sodium hydroxide, often known as lye or caustic soda, is a strong base formed when sodium reacts with water. Known for its ability to create alkaline solutions, it's widely used in multiple industries.
In the reaction of sodium with water, sodium hydroxide is formed, making the resulting solution highly alkaline and able to conduct electricity. Understanding its properties is essential:

• It's used in soap making, detergents, paper manufacturing, and more.
• Has the ability to neutralize acids, making it valuable in chemical processing.
• Safety precautions are necessary when handling sodium hydroxide due to its corrosive nature.

The formation of sodium hydroxide in reactions involving sodium is an important aspect of chemical studies, highlighting the utility and behavior of sodium compounds.

Oxygen Release

Releasing oxygen in chemical reactions is a common process and can be crucial for various applications. When sodium peroxide dissolves in water, it not only forms sodium hydroxide but also releases oxygen gas.
This type of reaction is important in producing oxygen in confined spaces, such as submarines or spacecraft. The simplicity of the process, using just water, underscores its practical value. Here's the chemical equation:

• $$2N{a}_2{O}_2+2H_{2}O\to 4NaOH+O_2$$
• Oxygen released can be used for combustion or respiratory purposes.
• It illustrates how compounds can store and release gases under chemical reactions.

Understanding the mechanisms behind oxygen release during such reactions contributes to advancements in safe and efficient oxygen production.