Write a balanced chemical equation for the reaction of solid potassium with liquid water.
The correct answer and explanation is:
The balanced chemical equation for the reaction of solid potassium with liquid water is:
2K (s)+2H2O (l)→2KOH (aq)+H2(g)2 \text{K (s)} + 2 \text{H}_2\text{O (l)} \rightarrow 2 \text{KOH (aq)} + \text{H}_2 \text{(g)}
Explanation:
In this reaction, potassium (K), a highly reactive alkali metal, reacts with water (H₂O) to form potassium hydroxide (KOH) and hydrogen gas (H₂). Here’s a breakdown of what happens:
- Potassium reacts with water: Potassium is an alkali metal, which means it has a single electron in its outermost shell. Alkali metals are known for their high reactivity, especially with water. When potassium is placed in water, it donates this outer electron to the water molecules.
- Formation of potassium hydroxide: The potassium ion (K⁺) reacts with the hydroxide ion (OH⁻) in water, forming potassium hydroxide (KOH), which dissolves in the water to produce an alkaline solution.
- Hydrogen gas production: The hydrogen ions (H⁺) from the water combine with the excess electrons from the potassium to form hydrogen gas (H₂). This gas is released in the process and often causes the reaction to bubble or fizz. The release of hydrogen gas is one of the reasons why this reaction is exothermic (it releases heat), and it can be violent, often producing a visible flame.
- Balancing the equation: To balance the equation, you must ensure that the number of atoms for each element is the same on both sides. For this reaction:
- Potassium (K) atoms: 2 K atoms on the left and 2 K atoms in KOH on the right.
- Water molecules: 2 H₂O molecules on the left balance with 2 KOH molecules on the right.
- Hydrogen gas: 1 molecule of H₂ is produced from the reaction, balancing the hydrogen atoms.
This reaction is typical of alkali metals in water and demonstrates both the reactivity of potassium and the production of hydrogen gas in the process.