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18. In a redox titration, potassium permanganate, KMnO4, was standardized using a 19.60 g/L
FeSO4(NH4)SO4.6H2O, (molar mass = 392.21 g/mol) standard solution. A 20.00 mL of the
standard solution, acidified with H2SO4 was put in a conical flask. A titre volume 15.50
mL of KMnO4 solution was required to reach the end-point. The titration reaction is:
Fe2+(aq) + MnO4
−(aq) → Fe3+(aq) + Mn2+(aq)
(i) Balance the above redox reaction in basic medium.
(ii) Calculate the molarity of the standard solution.
(iii) Determine molarity of MnO4-(aq) in the burette.
1. Human colour vision is “produced” by the nervous system based on how three different cone receptors interact with photons of light in the eye. These three different types of cones interact with photons of different frequency light, as indicated in the following chart:
Cone Type Range of Light Frequency Detected
S 6.00-7.49 x 1014 s-1
M 4.76-6.62 x 1014 s-1
L 4.28-6.00 x 1014 s-1
What wavelength ranges (and corresponding colours) do the three types of cones
detect?
1. Subshells half-filled with electrons are particularly stable. Can you suggest a possible
physical basis for this claim?
If an average fluorine atom has a mass of 3.16×10-23 g, what is the average mass of a chlorine atom in grams?
Calculate the ΔG° using Hess Law for the reaction: Cu2S(S) + O2(g) ( Cu(s) SO2(g)
2 Cu(s) + S(s) ( Cu2S(L) Δ Go = -86.2 kJ
S(s) + O2(g) ( SO2(g) Δ Go = -300.1 kJ
Calculate the entropy change, So for the following process.
a. Melting of ice at 0°C (heat of fusion of ice is 6.02 kJ/mol)
b. Freezing of 20.0 g liquid metal mercury at -38.9°C. (molar enthalpy of fusion of mercury is 2.33 kJ/mol)
Calculate the entropy change, S° for the following reactions using tabulated standard entropy values and figure out if the resulting values obtained are consistent with the expected entropy change as predicted qualitatively.
Thermal decomposition of NaNO3
2 NaNO3(S) ( 2 NaNO2(s) + O2(g)
So values at 25°C:
NaNO3(S) = 116.5 J/mol-K
NaNO2(s) = 103.8 J/mol-K
O2(g) = 205 J/mol-K
NiCl3 is a strong electrolyte.
Determine the concentration of each of the individual ions in a 0.550 M NiCl3
0.550 M NiCl3 solution.
Calculate the chloride ion (Cl−)
(Cl−) concentration for a 0.183 M AlCl3
0.183 M AlCl3 solution.
A student needs to prepare 50.0 mL
50.0 mL of a 0.90 M
0.90 M aqueous H2O2 solution. Calculate the volume of 4.6 M H2O2
stock solution that should be used to prepare the solution.
