When rubidium (Rb), an alkali metal, reacts with water, the reaction is quite intense, producing rubidium hydroxide (RbOH) and hydrogen gas (H₂). This reaction is a typical example of how alkali metals behave when they come in contact with water. But, how exactly does it happen, and what is the chemical equation?
The Reaction Between Rubidium and Water
Rubidium, like other alkali metals (such as lithium, sodium, and potassium), is highly reactive with water. When rubidium comes into contact with water, it reacts violently, generating heat, hydrogen gas, and a strong base—rubidium hydroxide.
The reaction can be written as:
2Rb (s) + 2H₂O (l) → 2RbOH (aq) + H₂ (g)
Here’s a breakdown of what’s happening:
- Rb (s): Solid rubidium metal
- H₂O (l): Liquid water
- RbOH (aq): Rubidium hydroxide, which dissolves in water, forming an alkaline solution
- H₂ (g): Hydrogen gas, which is released as a byproduct
What Happens During the Reaction?
When rubidium is dropped into water, it begins to dissolve in the water, forming rubidium hydroxide (RbOH) and releasing hydrogen gas (H₂). The reaction is highly exothermic, meaning it releases a lot of energy in the form of heat. The heat generated is so intense that it can ignite the hydrogen gas, often resulting in a fire or even an explosion.
The reaction can be visually striking, with the metal rapidly moving around in the water, producing bubbles of hydrogen gas. Because of the high reactivity of rubidium (and other alkali metals), the reaction is much more violent than with less reactive metals like sodium or potassium.
Why is Rubidium So Reactive?
Rubidium is part of the alkali metal group in the periodic table, and these metals are known for their high reactivity. The reactivity of alkali metals increases as you move down the group. Rubidium, being lower in the group than lithium, sodium, or potassium, is more reactive due to the following reasons:
- Large atomic size: Rubidium has a larger atomic radius, meaning its outermost electron is farther from the nucleus and more easily lost.
- Low ionization energy: Rubidium requires less energy to remove its outermost electron, making it highly reactive.
- Highly exothermic reactions: The loss of an electron from rubidium when it reacts with water releases a significant amount of energy.
Safety Note
The reaction of rubidium with water is not only violent but also dangerous. It’s important to handle rubidium with caution in a controlled laboratory environment, as the heat and hydrogen gas produced can lead to fires or explosions. Always follow proper safety protocols when dealing with reactive metals.
Conclusion
In summary, when rubidium reacts with water, the chemical equation is:
2Rb (s) + 2H₂O (l) → 2RbOH (aq) + H₂ (g)
This reaction is a classic example of the intense reactivity of alkali metals with water. Understanding this chemical process highlights the fascinating and sometimes dangerous nature of these elements and serves as a reminder of the need for careful handling of such reactive substances.