71. Which one of the following four metals would be displaced from the solution of its salts by other three metals?
(A) Mg
(B) Ag
(C) Zn
(D) Cu
Answer:
(B) Ag
Explanation:
In the chemical reactivity series, a more reactive metal displaces a less reactive one. Silver (Ag) is the least reactive among the given options, meaning it will be displaced by Mg, Zn, and Cu.
72. Reaction between X and Y, forms compound Z. X loses electron and Y gains electron. Which of the following properties is not shown by Z?
(A) Has high melting point
(B) Has low melting point
(C) conducts electricity in molten state
(D) occurs as solid
Answer:
(B) Has low melting point
Explanation:
Because electrons are completely transferred, Z is an ionic compound. Ionic compounds inherently exhibit strong electrostatic forces, giving them solid crystal lattices and very high melting points.
73. The displacement reaction between iron (III) oxide and a metal X is used for welding the rail tracks. Here X is:
(A) Copper granules
(B) Magnesium ribbon
(C) Sodium pellets
(D) Aluminium dust
Answer:
(D) Aluminium dust
Explanation:
This process is known as the thermite reaction. Aluminium dust acts as a powerful reducing agent, displacing iron from iron(III) oxide to produce molten iron used for welding tracks.
74. Consider the following reaction: . Identify x and y:
(A) Cu and (s)
(B) Ag and (l)
(C) Ag and (s)
(D) and (l)
Answer:
(C) Ag and (s)
Explanation:
In this single displacement reaction, solid copper displaces silver from the aqueous silver nitrate solution, precipitating solid silver metal. Thus, is Ag, and its state is solid (s).
75. In the decomposition of solid , the gas evolved is:
(A)
(B)
(C)
(D)
Answer:
(B)
Explanation:
Heating ferrous sulfate crystals heavily decomposes them to form solid ferric oxide () while releasing two distinct gases: sulfur dioxide () and sulfur trioxide ().
