Chemistry 1 Marks Question

Mg > Al > Zn > Fe > Cu is decreasing order of their reactivity.

According to the question,
Fe²⁺ → Fe³⁺ + e^-1
Electricity required for the oxidation of 1 mol of FeO to Fe₂O₃ = 1 F
= 96487 C

Methane and Methanol.

The conductivity of a solution is the conductance of ions present in a unit volume of the solution. The number of ions (responsible for carrying current) decreases when the solution is diluted. As a result, the conductivity of a solution decreases with dilution.

MnO^-₄ → Mn²⁺
i.e., Mn⁷⁺ + 5e^- → Mn²⁺
Therefore, Required charge = 5 F
= 5 × 96487 C
= 482435 C

Ag < Hg < Cr < Mg < K.

Al³⁺ + 3e^- → Al
Therefore, Required charge = 3 F
= 3 × 96487 C
= 289461 C

Cu²⁺ + 2e^- → Cu
Therefore, Required charge = 2 F
= 3 × 96487 C
= 192974 C

Cr₂O₇^2– → 2Cr³⁺
2Cr⁶⁺ + 6e^– → 2Cr³⁺
In given equation there are 6 electrons are required so that n = 6
Use the formula
Required charge = nF
Plug the values in this formula we get
Required charge = 6 × 96487 Coulombs
= 578922 Coulombs
= 5.79 × 10⁵ Coulombs

Na, Ca, Mg and Al

It is molar conductivity at infinite dilution or approaching zero concentration.

Zink is better than tin in protecting iron from corrosion because zink has more affinity to oxygen than tin. When is coated on iron layer then it reacts with oxygen if air to form a protective layer of zink oxide on iron which prevent the further reaction of iron with oxygen, and thus preventing the process of rusting. But in the case of tin, it(tin) does not react with oxygen thus it is less effective in preventing rusting.

A, as its standard reduction potential is less than B, therefore, it will undergo oxidation more easily than B.

To complete the inner circuit and to maintain the electrical neutrality of the electrolytic solutions of the half-cells we use a salt bridge in a Galvanic cell.

It means that Zn is more reactive than hydrogen. When zinc electrode will be connected to SHE, Zn will get oxidised and H⁺ will get reduced.

As the reaction proceeds, concentration of ions in anodic half keeps on increasing while in the cathodic half it keeps on decreasing. Hence, their electrode potentials also keep on changing till ultimately they become equal and then e.m.f. of the cell becomes zero.

As iron (-0.44V) has lower standard reduction potential than C (-0.20V) only therefore when coating is broken, rusting will take place faster.

Alternating current is used to prevent electrolysis so that concentration of ions in the solution remains constant.

The arrangement of elements in the increasing or decreasing order of their standard reduction potentials is called electrochemical series.

3. Conductivity does not depend upon solvation of ions present in solution.

Explanation:

Conductivity depends upon salvation of ions present in the solution. The greater the salvation of ions, the lesser is the conductivity.

Under the conditions of electrolysis of aqueous sodium chloride, oxidation of water at anode requires overpotential hence Cl^- is oxidised instead of water.

The electrical potential difference set up between the metal and its solution is called electrode potential.

On the addition of water, number of ions per unit volume decreases and therefore conductivity decreases.

This is because of the fact that standard reduction potential of water is greater than that of sodium.

Oxidation or reduction cannot take place alone. Moreover, electrode potential is a relative tendency and can be measured with respect to a reference electrode only.

Concentration of Mg 2+ and Ag+ ions in the solution and temperature.

Ions.

Fe₂O₃. _xH₂O

The process of coating zinc over iron is called galvanization.

Specific conductance is defined as conductance of electrolyte when distance between electrodes is 1cm and area of cross section is 1cm².

Normal hydrogen electrode (NHE).

Even though not in use, a dry cell becomes dead after some time because the acidic NH₄Cl corrodes the zinc container.

No, absolute electrode potential of an electrode cannot be measured.