Give the cell diagram notation of the electrochemical cell that could be used to determine experimentally the dissociation constant (Kw) of water.
The standard reduction potential for:
O2 + 2H20 + 4e- ---------> 4 OH- 0.40 V
To determine the dissociation constant (Kw) of water experimentally, we can use an electrochemical cell with a known reduction potential for the reaction involving oxygen and water.
The cell diagram notation for the electrochemical cell can be written as follows:
Pt | H2(g)/H+(aq) || OH-(aq) | O2(g) | Pt
Let's break down the notation:
1. The Pt on either side of the cell notation represents platinum electrodes. They act as catalysts and do not participate in the chemical reactions.
2. The vertical line (||) separates the two half-cells.
3. On the left side of the vertical line, we have the H2(g)/H+(aq) half-cell. This consists of a hydrogen gas electrode and an acidic solution containing H+ ions.
4. On the right side of the vertical line, we have the OH-(aq)/O2(g) half-cell. This consists of an alkaline solution containing OH- ions and an oxygen gas electrode.
Now, to measure the dissociation constant (Kw) of water, we will adjust the concentrations of H+ and OH- ions and measure the potential difference between the two electrodes.
By maintaining a constant partial pressure of O2 gas, we can measure the potential difference between the two half-cells. The measured value can be used to calculate the concentration of OH- ions, which is related to the dissociation constant (Kw) of water.
Note: It is important to keep in mind that the given reduction potential for the reaction involving oxygen and water is not directly related to the dissociation constant (Kw). However, it can be used in combination with other reactions to indirectly determine Kw experimentally.