There is a solved exercise for Class 10 Chemistry (Electrochemistry) with the most important short questions. All notes for class 10 chemistry are here, and All Video lectures are here. Watch and Subscribe, please.
A: Multiple Choice Questions (MCQs)
| Q.No. | Question Statement | Correct Option | Answer Text |
|---|---|---|---|
| 1 | The oxidation number of Mn in K2MnO4: | (c) | +6 |
| 2 | Which element in the following reaction is being reduced? 4HBr + MnO2 → MnBr2 + Br2 + 2H2O | (b) | Mn |
| 3 | During electrolysis of dilute solution of H2SO4, using Pt electrodes, which process takes place at the cathode? | (a) | Reduction |
| 4 | Which product you will get at the anode when an aqueous solution of CuSO4 is electrolysed using copper electrodes? | (d) | No product, instead copper metal will go into the solution as Cu2+ |
| 5 | Which of the following statements is NOT correct about Zn-Cu electrochemical cell? | (b) | Reduction occurs at anode |
| 6 | Which product will be obtained at the anode when a concentrated solution of NaCl will be electrolysed? | (a) | Cl2 |
| 7 | When a dilute aqueous solution of ZnCl2 is electrolysed which product you will get at the cathode? | (a) | H2 |
| 8 | What is produced at the cathode in hydrogen-oxygen fuel cell? | (d) | OH1- |
| 9 | Which of the following metals is highest in the electrochemical series? | (c) | Magnesium |
B: Short Answer Questions (solved exercise)
16.1 What happens when electricity is passed through an aqueous solution of NaCl?
Ans: When electricity is passed through an aqueous solution of NaCl (brine), electrolysis takes place. Hydrogen gas (H2) is produced at the cathode, chlorine gas (Cl2) is produced at the anode, and sodium hydroxide (NaOH) remains in the solution as a by-product.
16.2 What are the main objectives of electroplating?
Ans: The two main objectives of electroplating are:
- Decoration: Coating inexpensive metals with noble metals like gold and silver to enhance their appearance.
- Protection: Protecting base metals from atmospheric corrosion, rusting, and the action of organic acids.
16.3 Mention one difference between an electrolytic cell and a galvanic cell.
Ans: An electrolytic cell converts electrical energy into chemical energy to drive a non-spontaneous redox reaction, whereas a galvanic cell converts chemical energy into electrical energy through a spontaneous redox reaction.
C: Constructed Response Questions (solved exercise)
16.1 Calculate the oxidation number of the chlorine atom in Ca(ClO3)2.
Ans: Let the oxidation number of Cl be x. Since the sum of oxidation states in a neutral compound is zero:
(+2) + 2[x + 3(-2)] = 0
+2 + 2[x – 6] = 0
+2 + 2x – 12 = 0
2x – 10 = 0 ⇒ 2x = +10 ⇒ x = +5
16.2 How can H2O2 behave as an oxidizing agent?
Ans: In H2O2, oxygen is in a -1 oxidation state, which is unstable. It acts as an oxidizing agent by gaining electrons to be reduced to a stable -2 oxidation state (forming H2O), as shown in the half-reaction:
H2O2 + 2H+ + 2e– → 2H2O
16.3 Why are different products formed at the electrodes when dilute and concentrated aqueous solutions of NaCl are electrolysed?
Ans: This is due to the preferential discharge of ions governed by concentration. In a concentrated solution, Cl– ions are in excess and are preferentially discharged at the anode to form Cl2 gas. In a dilute solution, the concentration of Cl– is very low, so OH- ions from water are preferentially discharged to form O2 gas.
16.4 Why does corrosion become fast during the rainy season?
Ans: Corrosion (rusting) requires both oxygen and moisture. During the rainy season, the high humidity provides abundant water on the metal surface, which dissolves atmospheric gases to form an effective electrolytic film, thereby accelerating the electrochemical process of rusting.
16.5 If a galvanic cell is established between Cu and Ag, what reactions do you expect at the electrodes?
Ans: Copper (Cu) is higher than silver (Ag) in the electrochemical series; hence, Cu acts as the anode (oxidation) and Ag acts as the cathode (reduction):
- At Anode (Oxidation): Cu(s) → Cu2+(aq) + 2e-
- At Cathode (Reduction): Ag+(aq) + e- → Ag(s)
16.6 What is the function of a porous partition in a galvanic cell?
Ans: The porous partition allows the migration of ions between the two half-cells to maintain electrical neutrality and complete the internal circuit while preventing the mechanical mixing of the two electrolytic solutions.
16.7 How do fuel cells produce electricity?
Ans: Fuel cells produce electricity by directly converting the chemical bond energy of a continuously supplied fuel (such as hydrogen) and an oxidizing agent (such as oxygen) into electrical energy through catalytic redox reactions without combustion.
16.8 How can the chemical reactivity of metals be compared by using the electrochemical series?
Ans: Metals placed higher in the electrochemical series have a greater tendency to lose electrons (stronger reducing agents) and are therefore chemically more reactive. Conversely, metals placed lower have a lower tendency to lose electrons and are less reactive.
Most Important short questions (Internal).
All questions are explained in Sir Umair Khan’s lecture.
- What is the use (importance) of oxidation number?
- Define oxidation number.
- What are the oxidation numbers for group 1, 2, and 3 elements?
- Discuss the oxidation number for hydrogen.
- How to write a chemical formula of calcium chloride using oxidation numbers.
- Define oxidation and give examples.
- In the following equations, which species is oxidised and which one is reduced?
CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)
4HCl(aq)+ MnO2(s) → MnCl2(aq)+ Cl2(g) +2H2O(l)
- Copper is called a reducing agent, prove with an example.
- Define reduction and give some examples.
- Define redox reaction.
- Define electrolysis
- Differentiate between spontaneous and non-spontaneous chemical reactions.
- Write about the process of electrolysis.
- Differentiate between anode and cathode in electrochemical cells.
- Define a fuel cell, and give one example.
- What kind of reactions take place in the fuel cell at the anode and cathode?
- What are the advantages of a fuel cell?
- What are the disadvantages of a fuel cell?
- Define the process of corrosion with an example.
- How does coating of the metal surface protect it from corrosion?
- How galvanization is important to prevent corrosion of metal.
- What is sacrificial protection of metal?
- What is electroplating? How is it useful?
- What are the properties of electrolytes chosen in electrochemical processes?
- What kind of conditions should be filled to deposit a good amount of noble metal when it is electroplated?
- Write about silver plating.
- Write a few lines about copper plating.
- What is a galvanic cell? How is it useful?
- Write down the construction of a galvanic cell.
- How a galvanic cell works, give an example by taking zinc as the anode and copper as the cathode.
- How the reactivity of metals can be found out by using voltage data.
- Define electrochemical series.
