Electrochemistry MCQs for MDCAT

Correct answer: C. Is independent of the nature of the gas in discharge tube

Cathode rays consist of electrons and are independent of the nature of the gas used in the discharge tube, since electrons are a universal constituent of all matter.

Correct answer: D. Allow movement of ions between two half cells

A salt bridge in an electrolytic (or galvanic) cell allows the movement of ions between the two half-cells, completing the circuit and maintaining electrical neutrality.

Correct answer: D. -1

In MgCl2, chlorine exists as the chloride ion with an oxidation state of -1, balancing magnesium's +2 charge.

Correct answer: D. +6

In SO4^2-, with oxygen at -2 each (total -8) and an overall charge of -2, sulfur must have an oxidation number of +6 to balance the equation.

Correct answer: C. +7, +6, +4, +2

The oxidation states of manganese are +7 in KMnO4, +6 in K2MnO4, +4 in MnO2, and +2 in MnSO4.

Correct answer: B. +3

In K3[Fe(CN)6], with K contributing +3 total and each CN- ligand contributing -1 (6 × -1 = -6), iron must have an oxidation state of +3 to balance the overall neutral charge.

Correct answer: B. Redox reaction

An electrochemical cell is based on a redox reaction. Redox reactions involve the transfer of electrons between species. In an electrochemical cell, this transfer of electrons is facilitated through the separation of the oxidation and reduction half-reactions, which occur at different electrodes.

Correct answer: C. Mn+2

Mn²⁺: Manganese in the +2 oxidation state has an electron configuration of [Ar] 3d⁵, which is a half-filled d-subshell, making it stable.

Correct answer: A. Split the reaction into two half reactions.

Option A is correct. That step belongs to the ion–electron (half-reaction) method, not the oxidation number method.In the oxidation number method, you:Assign oxidation numbers.Identify atoms changing oxidation state.Equalize the total increase and decrease in oxidation number.Balance the remaining atoms and charges.So, splitting into half-reactions is not required here.

Correct answer: D. +7

In KMnO₄, Mn has an oxidation number of +7. This is determined by balancing the oxidation states of the other elements (K and O) in the compound, and it is one of the highest oxidation states Mn can achieve in compounds.

Correct answer: A. III

In the given complex, [Co(H2NCH2CH2NH2)3]2(SO4)3 Cobalt is bonded with three molecules of ethylenediamine which is a bidendate ligand having neutral charge. Moreover the coordination sphere is bonded with three molecules of sulphate ions each having -2 charge. Using formula: Charge of Metal + Charge on Ligand + Charge on coordination sphere 2(x + 3(0) ) = 3(-2) 2x = -6 x = -3

Correct answer: D. 2H2O —> O2(g) +4H+ + 4e

Here's a breakdown of the electrolysis of water:Cathode: Water is reduced to hydrogen gas. 2H+ + 2e- -> H2(g) Anode: Water is oxidized to oxygen gas. 2H2O -> O2(g) + 4H+ + 4e- The overall reaction is the sum of these two half-reactions:2H2O -> 2H2(g) + O2(g)Therefore, the correct answer is d, which represents the overall reaction at the anode.