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The MCQs below are drawn from the Chemistry subject category.
Showing 2531–2540
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2531
Evaluate the following statements regarding a galvanic cell: 1. It converts chemical energy into electrical energy. 2. Electrons flow from anode to cathode through the external circuit. 3. It converts metal from its elemental state to the combined state.
A galvanic cell converts chemical energy into electrical energy via spontaneous redox reactions. Electrons flow from the anode (oxidation) to the cathode (reduction) through an external circuit. Statement 3 is incorrect because while the anode metal is oxidized to ions, the cathode metal ions are reduced to the elemental state, meaning the overall process involves both oxidation and reduction, not just conversion to a combined state.
2532
Which product is generated at the cathode during the electrolysis of an aqueous sodium chloride solution?
During the electrolysis of brine (aqueous NaCl), chloride ions are oxidized to chlorine gas at the anode, while water is reduced to hydrogen gas and hydroxide ions at the cathode. The accumulation of Na+ and OH- ions results in the formation of sodium hydroxide in the solution.
2533
What are the primary products formed when electricity is passed through an aqueous solution of sodium chloride (brine)?
The electrolysis of brine (aqueous NaCl) is known as the chlor-alkali process. At the cathode, water is reduced to hydrogen gas and hydroxide ions, while at the anode, chloride ions are oxidized to chlorine gas. This results in the production of sodium hydroxide, hydrogen, and chlorine.
2534
What chemical species is displaced when zinc metal is added to an aqueous copper sulphate solution?
This is a classic single-displacement reaction. Zinc is more reactive than copper in the electrochemical series. Therefore, zinc displaces copper ions from the copper sulphate solution, forming zinc sulphate and solid copper metal. The reaction is: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s).
2535
What is the name of the electrolytic process used to create a thick, protective oxide layer on the surface of aluminium?
Anodizing is an electrochemical process that increases the thickness of the natural oxide layer on the surface of metal parts. For aluminium, this process creates a durable, corrosion-resistant, and aesthetically pleasing finish by making the metal the anode in an electrolytic cell.
2536
Why does molten sodium chloride (NaCl) exhibit electrical conductivity?
In solid sodium chloride, ions are locked in a rigid crystal lattice and cannot move. When melted, the lattice structure breaks down, allowing the sodium (Na+) and chloride (Cl-) ions to move freely throughout the liquid. These mobile charged particles act as charge carriers, enabling the molten salt to conduct electricity effectively.
2537
In the process of electroplating a spoon with nickel, how should the components be arranged in the electrolytic cell?
For electroplating, the object to be plated (the spoon) must act as the cathode, where reduction occurs, allowing nickel ions to deposit as metallic nickel. The pure nickel rod serves as the anode, which oxidizes to replenish the nickel ions in the electrolyte solution, typically nickel sulfate.
2538
What method is used to deposit a thin film of gold onto jewelry made of base metals like copper or nickel when placed in a gold salt solution?
Electroplating is the process of using an electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode. To deposit gold onto a base metal, the object is placed in a solution containing gold ions and an external current is applied to drive the reduction of gold ions onto the surface.
2539
In galvanic cell Zn acts as an anode so its value of standard reduction potential in comparison to coupled electrode would be________________?
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Downs cell is an electrolytic cell used for the commercial production of sodium metal. It involves the electrolysis of molten sodium chloride, producing sodium metal at the cathode. This process is crucial for obtaining pure sodium metal.
