Mix Example - IS MATTER AROUND US PURE? Questions in English

(C) An element is a pure substance consisting only of atoms that all have the same number of protons in their atomic nuclei.
$A$. Carbon dioxide $(CO_2)$ is a compound made of carbon and oxygen atoms.
$B$. Sulphur dioxide $(SO_2)$ is a compound made of sulphur and oxygen atoms.
$C$. Oxygen gas $(O_2)$ consists only of oxygen atoms,making it an element.
$D$. Nitrogen dioxide $(NO_2)$ is a compound made of nitrogen and oxygen atoms.
Therefore,the correct option is $C$.

(C) homogeneous mixture is a mixture in which the components are uniformly distributed throughout the mixture.
Soda water,copper sulphate solution,and sodium chloride solution are all examples of homogeneous mixtures (solutions).
However,in the context of standard textbook questions of this type,if multiple options appear correct,we look for the most representative example of a true solution.
Actually,all options $A$,$B$,and $C$ are homogeneous mixtures. Starch solution is a colloid,which is heterogeneous.
Assuming the question implies selecting the most common laboratory example of a true solution,$C$ (Sodium chloride solution) is a classic example. However,since $A$,$B$,and $C$ are all technically homogeneous,this question is often presented with specific options. Given the standard classification,$A$,$B$,and $C$ are all homogeneous. If this is a single-choice question,there might be an error in the provided options as multiple are correct. For the purpose of this format,we identify $C$ as a standard homogeneous solution.

(A) pure substance consists of particles of only one type of chemical nature. Elements and compounds are considered pure substances.
$CaO$ (Calcium oxide), $CO_2$ (Carbon dioxide), and $NaCl$ (Sodium chloride) are all chemical compounds with fixed compositions.
Brick is a mixture of various materials, mercury is an element (pure), but wood is a complex mixture.
Iron is an element (pure), $CaO$ is a compound (pure), but air is a mixture of gases.
Ice is pure water $(H_2O)$, but milk is a colloid (mixture of water, fats, proteins, etc.).
Therefore, the group containing only pure substances is $CaO, CO_2$ and $NaCl$.

(B) An aqueous solution is a solution in which the solvent is water.
In the given options,sodium chloride $(NaCl)$ dissolved in water forms an aqueous solution because water acts as the solvent.
Sulphur in carbon disulphide,iodine in carbon tetrachloride,and sugar in alcohol are non-aqueous solutions because the solvents used are organic liquids,not water.

(C) Sublimation is the process where a solid directly changes into a gas without passing through the liquid state at atmospheric pressure.
To liquefy a substance that normally sublimes,we must increase the pressure on the substance.
By applying high pressure,the intermolecular forces become strong enough to maintain the liquid phase.
Therefore,substances that sublime can be made to liquefy by heating or compressing them under high pressure,which prevents them from transitioning directly to the gaseous state.

(D) Sublimation is the process in which a solid changes directly into a gas without passing through the liquid state.
Substances that exhibit this property are known as sublimable substances.
Iodine,camphor,ammonium chloride $(NH_4Cl)$,anthracene,and naphthalene are well-known examples of substances that sublime easily upon heating.
Petrol,acetone,kerosene,and diesel are liquids at room temperature and do not sublime.
Therefore,the correct group of substances is iodine,camphor,ammonium chloride,anthracene,and naphthalene.

(B) Chromatography is a laboratory technique used for the separation of a mixture into its individual components.
It works on the principle that different components of a mixture have different affinities for the stationary phase and the mobile phase.
As the mixture moves through the stationary phase,the components are adsorbed to different extents based on their chemical properties.
This difference in the extent of adsorption causes the components to travel at different speeds,leading to their separation.

(B) pure substance consists of only one type of particles (atoms or molecules). Therefore,statement $(i)$ is true.
Pure substances are either elements or compounds,not mixtures. Therefore,statement $(ii)$ is false.
Pure substances have a fixed chemical composition and uniform properties throughout. Therefore,statement $(iii)$ is true.
Elements like nickel are pure substances; the claim that all elements except nickel are pure substances is incorrect. Therefore,statement $(iv)$ is false.
Thus,statements $(i)$ and $(iii)$ are correct.

(C) Rusting of iron is a process where iron reacts with oxygen and moisture in the air to form hydrated iron $(III)$ oxide $(Fe_2O_3 \cdot xH_2O)$.
This process is known as corrosion.
Since a new substance with different chemical properties is formed, it is a chemical change.
Therefore, rusting is corrosion and it is a chemical change.

(D) Sulphur is soluble in carbon disulphide $(CS_2)$.
When sulphur is dissolved in carbon disulphide,it forms a true solution.
$A$ true solution is a homogeneous mixture where the particles are smaller than $1 \ nm$ in diameter.
Because the particles are very small,they do not scatter a beam of light passing through the solution.
Therefore,a true solution does not show the Tyndall effect.
Thus,the mixture of sulphur and carbon disulphide is homogeneous and does not show the Tyndall effect.

(A) tincture of iodine is a well-known antiseptic solution.
It is prepared by dissolving $2-7\%$ of iodine in a mixture of alcohol and water.
Therefore, the correct composition is iodine dissolved in alcohol.

(B) homogeneous mixture is a mixture in which the composition is uniform throughout the mixture.
$(i)$ Ice is a pure substance ($H_2O$ in solid state),which is homogeneous.
$(ii)$ Wood is a heterogeneous mixture consisting of various fibers and compounds.
$(iii)$ Soil is a heterogeneous mixture containing sand,clay,organic matter,and minerals.
$(iv)$ Air is a homogeneous mixture of various gases like nitrogen,oxygen,argon,and carbon dioxide.
Therefore,both ice and air are homogeneous in nature.

(TRUE) The statement is True.
Physical properties are those characteristics of matter that can be observed or measured without changing the chemical identity of the substance. Examples include color,hardness,density,melting point,boiling point,and physical state (solid,liquid,or gas).

(B) The statement is False.
When a candle burns,both physical and chemical changes occur simultaneously.
$1$. Physical Change: The wax near the flame melts due to heat,changing from a solid state to a liquid state. This is a physical change because the chemical composition of the wax remains the same.
$2$. Chemical Change: The melted wax (vaporized) reacts with oxygen in the air to produce carbon dioxide,water vapor,heat,and light. This is a chemical change because new substances are formed.

(FALSE) The statement is False.
Non-metals are generally non-lustrous (dull) and are poor conductors of heat and electricity (insulators). Exceptions exist,such as graphite,which is a good conductor of electricity,but as a general rule,the statement is incorrect.

(A) The statement is True.
$1$. Malleability: Metals can be beaten into thin sheets.
$2$. Ductility: Metals can be drawn into thin wires.
$3$. Sonorous: Metals produce a ringing sound when struck.
$4$. Lustrous: Metals have a shiny appearance.

(TRUE) The statement is True.
$A$ compound is defined as a pure substance formed by the chemical combination of two or more elements in a fixed ratio by mass. The properties of a compound are entirely different from the properties of its constituent elements.