Question1. What is hydrodynamic voltammetry? State two (2) applications of voltammetry.
2. What is the potential of a cell consisting of a silver electrode dipped in silver nitrate solution with $[\mathrm{Ag}+]=0.01 \mathrm{M}$ and a standard calomel reference electrode $\left(\mathrm{E}_{\mathrm{ref}}=+0.242\right.$ V). Neglect liquid-junction potential.
3. Briefly describe a simple electrochemical cell used in potentiometric analysis. Write a cell diagram for this cell.
4. Calculate the ionic strengths of the following solutions A) 0.20 M NaCl and $0.30 \mathrm{M} \mathrm{Na}_{2} \mathrm{SO}_{4}$ B) $0.1 \mathrm{M} \mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$

Studdy Solution
Calculate the ionic strengths of the given solutions.
A) For $0.20 \, \text{M} \, \text{NaCl}$ and $0.30 \, \text{M} \, \text{Na}_2\text{SO}_4$:
The ionic strength $I$ is given by:
$$I = \frac{1}{2} \sum c_i z_i^2$$
For NaCl: - $c_{\text{Na}^+} = 0.20 \, \text{M}$, $z_{\text{Na}^+} = +1$ - $c_{\text{Cl}^-} = 0.20 \, \text{M}$, $z_{\text{Cl}^-} = -1$
$$I_{\text{NaCl}} = \frac{1}{2} \left( 0.20 \times 1^2 + 0.20 \times 1^2 \right)$$
$$I_{\text{NaCl}} = \frac{1}{2} \times 0.40 = 0.20 \, \text{M}$$
For Na2SO4: - $c_{\text{Na}^+} = 2 \times 0.30 = 0.60 \, \text{M}$, $z_{\text{Na}^+} = +1$ - $c_{\text{SO}_4^{2-}} = 0.30 \, \text{M}$, $z_{\text{SO}_4^{2-}} = -2$
$$I_{\text{Na}_2\text{SO}_4} = \frac{1}{2} \left( 0.60 \times 1^2 + 0.30 \times 2^2 \right)$$
$$I_{\text{Na}_2\text{SO}_4} = \frac{1}{2} \left( 0.60 + 1.20 \right)$$
$$I_{\text{Na}_2\text{SO}_4} = \frac{1}{2} \times 1.80 = 0.90 \, \text{M}$$
Total ionic strength for the mixture:
$$I_{\text{total}} = I_{\text{NaCl}} + I_{\text{Na}_2\text{SO}_4} = 0.20 + 0.90 = 1.10 \, \text{M}$$
B) For $0.1 \, \text{M} \, \text{K}_2\text{Cr}_2\text{O}_7$:
- $c_{\text{K}^+} = 2 \times 0.1 = 0.2 \, \text{M}$, $z_{\text{K}^+} = +1$ - $c_{\text{Cr}_2\text{O}_7^{2-}} = 0.1 \, \text{M}$, $z_{\text{Cr}_2\text{O}_7^{2-}} = -2$
$$I = \frac{1}{2} \left( 0.2 \times 1^2 + 0.1 \times 2^2 \right)$$
$$I = \frac{1}{2} \left( 0.2 + 0.4 \right)$$
$$I = \frac{1}{2} \times 0.6 = 0.3 \, \text{M}$$