Question

experiment 3
data sheet
name:
section:
unknown no
knowns
unknown - (your unknown may contain 1, 2 or 3 different cations. list their properties here.)
cu²⁺
fe³⁺
ni²⁺
co²⁺
a
b
c
d, cm
6.5
8
6
2
5.3
8
l, cm
2
r
x
color
red
dark blue
none
orange
purple
dark blue
x
show rf calculations
cations present in unknown:
draw a sketch of your chromatogram

Explanation:

Step1: Define $R_f$ formula

$R_f = \frac{D}{L}$
Where $D$ = distance solute traveled, $L$ = distance solvent traveled

Step2: Calculate $R_f$ for known cations

• $\text{Cu}^{2+}$: $R_f = \frac{6.5}{22} \approx 0.295$
• $\text{Fe}^{3+}$: $R_f = \frac{8}{22} \approx 0.364$
• $\text{Ni}^{2+}$: $R_f = \frac{0}{22} = 0$
• $\text{Co}^{2+}$: $R_f = \frac{2}{22} \approx 0.091$

Step3: Calculate $R_f$ for unknown spots

• Spot A: $R_f = \frac{5.3}{22} \approx 0.241$ (matches $\text{Cu}^{2+}$ closely)
• Spot B: $R_f = \frac{8}{22} \approx 0.364$ (matches $\text{Fe}^{3+}$ exactly)
• Spot C: No data, not present

Step4: Match color and $R_f$ values

Spot A (red) = $\text{Cu}^{2+}$; Spot B (dark rust) = $\text{Fe}^{3+}$

Answer:

Cations present in unknown: $\text{Cu}^{2+}$, $\text{Fe}^{3+}$ (no third cation present)
Chromatogram sketch summary:

• Solvent front (dashed line) at 22 cm from origin
• $\text{Cu}^{2+}$ (unknown spot A): red spot at 5.3 cm from origin
• $\text{Fe}^{3+}$ (unknown spot B): dark rust spot at 8 cm from origin
• No third spot detected for unknown C