Question 11.
Observe the relationship between the first two terms and fill in the blanks.
Strong electrolyte : NaOH
Weak electrolyte :………..
Predict the product of electrolysis in each of the following:
i. An aqueous solution of copper sulphate with platinum electrodes.
ii. An aqueous solution of sodium chloride.
Conductivity of ionic solutions are measured by using conductivity cell in Wheatstone bridge arrangement.
a. What do you meant by cell constant?
b. How is cell constant related to conductivity?
Conductance of an electrolyte depends upon temperature of electrolyte and concentration of the electrolytes.
i. Classify the following into strong and weak electrolyte.
KOH, CH3COOH, NaCI, NH4OH
ii. What happens to the molar conductivity of an electrolyte solution when diluted with water? Justify your
a. Write the reaction taking place at anode in the following cell:
Pt, H2 (1 atm) / HCI (1 m) Cl2, Pt.
b. Write the Nernst equation for cell potential of the following cell.
Pb(s) /Pb(NO3)2 (aq) IIHCI (aq)/H2(g)/ Pt.
In Apollo space programme the fuel cells are used not only for the electric power but also to prepare H2O for drinking. What are the advantages of fuel cell over ordinary cells?
The diagram below shows a Daniel cell which produces one volt.
a. Identify the anode and cathode.Represent the half cell reactions.
b. If magnesium was placed instead of Zinc, would you expect it to produce a greater or smaller voltage?Explain your
Conductivity of 0.00241 M acetic acid is 7.896 × 10-5 Scm-1. Calculate its molar conductivity. If λ°m for acetic acid is 390.5 Scm2 mol-1, what is its dissociation constant?
a. Mercury cell is a primary cell which can give a constant voltage through out its life. Explain why ?
b. Two metals P and Q have reduction potentials of -0.44 V and + 0.77 V respectively. Which metal can liberate hydrogen from dilute acids ?
Ramu found that an iron sample in contact with sand is corroded.
a. What is corrosion?
b. It is found that alkaline medium inhibits the rusting of iron. Explain.
Iron is galvanised for protecting it from rusting.
a. Galvanised iron is not used for making food containers. Why ?
b. Iron does not rust even if the zinc coating is broken in a galvanised iron pipe but rusting occurs much faster if the tin coating over iron is broken. Explain.
A student in a view to obtain sodium metal at the cathode, carried out the electrolysis of NaCI solution. He did not get sodium at the cathode, instead he got two gases at the electrodes.
i. …………… gas produced at each electrode.
ii. Why he did not get Sodium ?
A car battery is made of lead plate dipping into sulphuric acid (Lead Accumulator). It can be recharged.
a. Is there any change in the concentration of H2SO4 during discharging and recharging the cell?
b. When the battery is used a reaction takes place. Identify the change to this reaction when the battery is recharged and represent the reactions at the anode of the cell.
Nernst equation describes the variation of electrode potential with concentration and temperature.
a. Write cell reaction, overall reaction and calculate e.m.f at 25°C for the cell. Also write Nernst equation for the cell potential.
b. In a seminar one of the students represented a chart as follows.
Potential difference of a cell is always lass than e.m.f of the cell, Do you agree with the above statement? Justify.
Question 4.
a. Calculate the standard cell potentials of galvanic cell. Also calculate ΔG° and equilibrium constant of the following cell, reaction.
Fe2+(aq) + Ag+(aq) → Fe3+(aq) + Ag(s)
E0 Ag+IAg=0.80V; E° Fe3+IFe2+= 0.77V
b. Is the effect of dilution on the molar conductance of strong and weak electrolytes the same?
Galvanic cells are classified into primary and secondary cells
a. Write any two differences between primary cell and secondary cell.
b.
i. What is a fuel cell?
ii. Write the overall cell reaction in H2O2 fuel cell.
a. Conductance (G), conductivity (K) and molar conductivity (Λm )are terms used in electrolytic conduction.
1. Write any two factors on which conductivity depends on.
2. How do conductivity and molar conductivity vary with concentration of electrolytic solution ?
b. Write any one difference between primary cell and secondary cell.
Fuel cells are special types of galvanic cells.
a.
(i) What are galvanic cells?
(ii) Write any two advantages of fuel cells.
b.
Write the electrode reaction in H2 -O2 Fuel cell.
The standard electrode potentials of some electrodes are given below:
a. What is the reaction taking place at SHE when it is connected to Ag/Ag+ electrode to form a galvanic cell?
b. Find the value of Kc (equilibrium constant) in the Daniel cell at 298K.
Innumerable number of galvanic cells can be constructed on the pattern of Daniel cell by taking combination of different half-cells.
1. What is galvanic cell ?
2. Name the anode and cathode of the Daniel cell.
3. Write the name of the half cell represented by Pt(s)/H2 (g)/H+(aq).
4. What is the potential of the above half cell at all temperatures ?
