Answer :
Let's solve the given questions step by step.
### 4.1 Write down THREE conditions needed for these cells to function as standard cells.
For a cell to function as a standard cell, the following conditions need to be met:
1. Temperature: The temperature should be 25 degrees Celsius (298 K).
2. Concentration: The concentration of all aqueous solutions should be 1 Molar (1 M).
3. Pressure: The gas pressure should be 1 atmosphere (atm).
### 4.2 For Combination I, identify:
#### 4.2.1 The anode of the cell:
The anode is the electrode where oxidation occurs. In the net cell reaction for Combination I:
[tex]\[ Q^{2+}(aq) + Cd(s) \rightarrow Cd^{2+}(aq) + Q(s) \][/tex]
Cadmium (Cd) is being oxidized to \( Cd^{2+} \). Oxidation occurs at the anode, so the anode of the cell in Combination I is:
[tex]\[ \text{Anode: } Cd(s) \][/tex]
#### 4.2.2 Q by using a calculation:
To identify Q, we need to determine the reduction potential of the half-cell \( Q^{2+}/Q \).
The standard cell potential (E° cell) is given by the difference between the standard reduction potentials of the cathode and the anode:
[tex]\[ E^\circ_{\text{cell}} = E^\circ_{\text{cathode}} - E^\circ_{\text{anode}} \][/tex]
For Combination I, the measured cell potential is 0.13 V. The net cell reaction is:
[tex]\[ Q^{2+}(aq) + Cd(s) \rightarrow Cd^{2+}(aq) + Q(s) \][/tex]
Given:
- The standard reduction potential for \( Cd^{2+}/Cd \) is -0.40 V.
- The cell potential \( E^\circ_{\text{cell}} \) is 0.13 V.
Let \( E^\circ(Q^{2+}/Q) = x \). The cathode in this combination would be \( Q^{2+}/Q \), and the anode would be \( Cd^{2+}/Cd \).
Using the formula for the cell potential:
[tex]\[ 0.13 \, V = x - (-0.40 \, V) \][/tex]
[tex]\[ 0.13 \, V = x + 0.40 \, V \][/tex]
[tex]\[ x = 0.13 \, V - 0.40 \, V \][/tex]
[tex]\[ x = -0.27 \, V \][/tex]
Therefore, the reduction potential of \( Q^{2+}/Q \) is:
[tex]\[ E^\circ(Q^{2+}/Q) = -0.27 \, V \][/tex]
#### Final results:
1. Standard Conditions:
- Temperature: 25 degrees Celsius (298 K)
- Concentration: 1 Molar
- Pressure: 1 atmosphere (atm)
2. Anode in Combination I:
- Cd(s)
3. Reduction Potential of Q:
- [tex]\( -0.27 \, V \)[/tex]
### 4.1 Write down THREE conditions needed for these cells to function as standard cells.
For a cell to function as a standard cell, the following conditions need to be met:
1. Temperature: The temperature should be 25 degrees Celsius (298 K).
2. Concentration: The concentration of all aqueous solutions should be 1 Molar (1 M).
3. Pressure: The gas pressure should be 1 atmosphere (atm).
### 4.2 For Combination I, identify:
#### 4.2.1 The anode of the cell:
The anode is the electrode where oxidation occurs. In the net cell reaction for Combination I:
[tex]\[ Q^{2+}(aq) + Cd(s) \rightarrow Cd^{2+}(aq) + Q(s) \][/tex]
Cadmium (Cd) is being oxidized to \( Cd^{2+} \). Oxidation occurs at the anode, so the anode of the cell in Combination I is:
[tex]\[ \text{Anode: } Cd(s) \][/tex]
#### 4.2.2 Q by using a calculation:
To identify Q, we need to determine the reduction potential of the half-cell \( Q^{2+}/Q \).
The standard cell potential (E° cell) is given by the difference between the standard reduction potentials of the cathode and the anode:
[tex]\[ E^\circ_{\text{cell}} = E^\circ_{\text{cathode}} - E^\circ_{\text{anode}} \][/tex]
For Combination I, the measured cell potential is 0.13 V. The net cell reaction is:
[tex]\[ Q^{2+}(aq) + Cd(s) \rightarrow Cd^{2+}(aq) + Q(s) \][/tex]
Given:
- The standard reduction potential for \( Cd^{2+}/Cd \) is -0.40 V.
- The cell potential \( E^\circ_{\text{cell}} \) is 0.13 V.
Let \( E^\circ(Q^{2+}/Q) = x \). The cathode in this combination would be \( Q^{2+}/Q \), and the anode would be \( Cd^{2+}/Cd \).
Using the formula for the cell potential:
[tex]\[ 0.13 \, V = x - (-0.40 \, V) \][/tex]
[tex]\[ 0.13 \, V = x + 0.40 \, V \][/tex]
[tex]\[ x = 0.13 \, V - 0.40 \, V \][/tex]
[tex]\[ x = -0.27 \, V \][/tex]
Therefore, the reduction potential of \( Q^{2+}/Q \) is:
[tex]\[ E^\circ(Q^{2+}/Q) = -0.27 \, V \][/tex]
#### Final results:
1. Standard Conditions:
- Temperature: 25 degrees Celsius (298 K)
- Concentration: 1 Molar
- Pressure: 1 atmosphere (atm)
2. Anode in Combination I:
- Cd(s)
3. Reduction Potential of Q:
- [tex]\( -0.27 \, V \)[/tex]