This question tests the understanding of the fundamental differences between a mixture and a compound, specifically using the example of iron and sulfur. The key is to recall how the properties of constituents change (or don't change) when they form a mixture versus a chemical compound.
A) In the mixture, HCl added produces Hâ‚‚S gas (rotten egg smell) from sulfur. In the compound FeS, HCl produces Hâ‚‚S gas only after reacting with FeS (not separately from iron and sulfur). This statement is incorrect as written in the question. Let's re-evaluate. When HCl is added to a mixture of iron and sulfur, the iron reacts with HCl to produce hydrogen gas (\(H_2\)), and the sulfur remains unreacted. When HCl is added to the compound FeS, it reacts to produce hydrogen sulfide (\(H_2S\)) gas, which has a rotten egg smell. The option states that in the mixture, HCl produces Hâ‚‚S from sulfur, which is incorrect. Sulfur itself does not react with HCl to produce Hâ‚‚S. However, the second part of the statement, "In the compound FeS, HCl produces Hâ‚‚S gas only after reacting with FeS (not separately from iron and sulfur)\
The question asks for the definition of an alloy and why it is classified as a mixture rather than a compound. We need to understand the fundamental differences between mixtures and compounds, particularly in terms of chemical bonding and composition.
Correct Option: B) An alloy is a homogeneous mixture of metals (or a metal with non-metals) that has variable composition — its components are not chemically bonded and retain their individual properties. This option accurately describes an alloy as a homogeneous mixture, highlights its variable composition, and correctly states that its components are not chemically bonded and retain their individual properties, which are key characteristics of a mixture.
This question tests knowledge about common alloys and their constituent elements. Alloys are mixtures of two or more metals, or a metal and a non-metal, designed to have properties superior to their individual components. Identifying the correct composition of brass requires recalling basic chemistry facts.
Correct Option: C) Copper (Cu) and Zinc (Zn)
Brass is a well-known alloy primarily composed of copper (Cu) and zinc (Zn). The proportions of copper and zinc can vary to create different types of brass with varying mechanical, electrical, and chemical properties. It is widely used for decorative items, musical instruments, and plumbing due to its workability, corrosion resistance, and attractive appearance.
The question asks to identify the pair of substances that can be separated most effectively into their original components using simple physical methods. This involves understanding the properties of mixtures and various separation techniques.
D) Iron filings and sulphur powder — iron can be extracted using a magnet, sulphur can be dissolved in carbon disulphide
The question asks to identify examples of 'solutions' as classified in NCERT Class 9 Chapter 2. To answer this, we need to recall the definitions and characteristics of solutions, colloids, and suspensions as described in that chapter.
Correct Option: C) Soda water, vinegar, filtered tea, sugar in water, copper sulphate solution. These are all homogeneous mixtures where the solute particles are uniformly distributed and do not settle down, fitting the description of a solution.
The question asks to identify the component of a solution that is present in a larger quantity and acts as the dissolving medium. This requires understanding the basic definitions of the components of a solution.
Correct Option: B) Solvent
The solvent is defined as the component of a solution that is present in the larger quantity and acts as the dissolving medium. For example, in a sugar solution, water is the solvent because it is present in a larger amount and dissolves the sugar.