Chemistry

141. Which one of the following is a compound ?

Which one of the following is a compound ?

[amp_mcq option1=”Milk” option2=”Sugar” option3=”Tea” option4=”Coffee” correct=”option2″]

This question was previously asked in
UPSC CAPF – 2010
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Among the given options, Sugar is a compound.
A compound is a substance formed when two or more different chemical elements are chemically bonded together in a fixed proportion. Milk, Tea, and Coffee are all mixtures. They consist of various substances physically mixed together, not chemically bonded in fixed ratios. “Sugar” typically refers to sucrose (C₁₂H₂₂O₁₁), which is a molecule composed of atoms of carbon, hydrogen, and oxygen chemically bonded in a fixed ratio, making it a compound.
A mixture is a substance consisting of two or more components not chemically combined. The components of a mixture retain their individual properties and can often be separated by physical means. Examples include air (mixture of gases), salt water (salt dissolved in water), milk, tea, and coffee.

142. Ice is lighter than pure water and floats on the surface. Which one of

Ice is lighter than pure water and floats on the surface. Which one of the following statements is correct to explain this phenomenon ?

[amp_mcq option1=”The structure of ice is similar to that of water” option2=”Ice has a disordered 3-dimensional structure” option3=”Hydrogen-bonding in ice gives an open type structure with interstitial holes” option4=”There is no hydrogen bonding in water” correct=”option3″]

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UPSC CAPF – 2010
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The correct statement explaining why ice is lighter than pure water is that hydrogen-bonding in ice gives an open type structure with interstitial holes.
In the solid state (ice), water molecules are held in a crystalline structure by hydrogen bonds. This structure is an open lattice containing hexagonal rings, with significant empty space or “interstitial holes” between the molecules. In the liquid state (water), although hydrogen bonds are still present and constantly breaking and reforming, the structure is less ordered and more compact than ice. As a result, a given mass of ice occupies a larger volume than the same mass of liquid water at the same temperature, leading to ice having a lower density and thus floating on water.
Most substances become denser in the solid state than in the liquid state. Water is unusual in this regard, exhibiting anomalous expansion (or contraction) upon melting or freezing. The density of water is maximum at 4°C. This property is crucial for aquatic life in cold climates, as ice forms on the surface, insulating the water below.

143. Sometimes, the consumption of local made alcoholic beverages may cause

Sometimes, the consumption of local made alcoholic beverages may cause blindness or even death. This may be because of contamination of the beverages with :

[amp_mcq option1=”Vinegar” option2=”Carbolic acid” option3=”Methyl alcohol” option4=”Formic acid” correct=”option3″]

This question was previously asked in
UPSC CAPF – 2009
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Blindness or death from consuming local made alcoholic beverages may be because of contamination with Methyl alcohol.
Ethanol (ethyl alcohol) is the alcohol intended for consumption in alcoholic beverages. Methanol (methyl alcohol) is a highly toxic substance that can be produced as a byproduct during improper fermentation or distillation, or sometimes illegally added to beverages. When ingested, methanol is metabolized by the body into formaldehyde and formic acid, which are potent toxins that damage the optic nerve (leading to blindness) and other organs, often resulting in death.
Vinegar is primarily acetic acid, which is relatively harmless in small quantities. Carbolic acid is phenol, a highly corrosive and toxic chemical. Formic acid is one of the toxic metabolites of methanol, but the primary contamination is usually with methanol itself.

144. In some parts of India, consumption of underground water causes mottle

In some parts of India, consumption of underground water causes mottled teeth and bone damage. Which one of the following is responsible for this malady ?

[amp_mcq option1=”Fluoride ion” option2=”Chloride ion” option3=”Oxide ion” option4=”Carbonate ion” correct=”option1″]

This question was previously asked in
UPSC CAPF – 2009
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Fluoride ion is responsible for mottled teeth and bone damage caused by consuming contaminated underground water in some parts of India.
Excessive intake of fluoride, primarily through drinking water, leads to a condition called fluorosis. Dental fluorosis causes discoloration and mottling of tooth enamel, especially during tooth development. Skeletal fluorosis affects bones, causing joint pain, stiffness, and in severe cases, crippling deformities. Many areas in India have groundwater naturally high in fluoride.
While fluoride is essential for strengthening teeth enamel in appropriate amounts, its excess can be harmful. Chloride, Oxide, and Carbonate ions are common in water but are not the primary cause of mottled teeth and bone damage in the way that excess fluoride is.

145. Match List-I with List-II and select the correct answer using the code

Match List-I with List-II and select the correct answer using the code given below :

List-I (Process)List-II (Contaminant)
A. Aeration followed by filtration1. Removal of colour
B. Reverse Osmosis2. Removal of microorganism
C. Filtration through activated carbon3. Removal of iron
D. Treatment with UV light4. Removal of excess salts

Code:

[amp_mcq option1=”3 1 4 2″ option2=”4 3 2 1″ option3=”3 4 1 2″ option4=”2 4 1 3″ correct=”option3″]

This question was previously asked in
UPSC CAPF – 2009
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The correct match between the water treatment processes and the contaminants removed is A-3, B-4, C-1, D-2.
– A. Aeration followed by filtration: Aeration oxidizes dissolved iron and manganese, forming precipitates that are then removed by filtration. Thus, it’s used for the removal of iron (3).
– B. Reverse Osmosis: This process uses a semipermeable membrane to remove dissolved salts and other impurities from water, effectively used for desalination or removal of excess salts (4).
– C. Filtration through activated carbon: Activated carbon is highly effective at adsorbing organic compounds, chlorine, and other substances that cause color, odor, and taste in water. Thus, it’s used for the removal of colour (1).
– D. Treatment with UV light: Ultraviolet (UV) light treatment is a disinfection method that inactivates microorganisms like bacteria and viruses by damaging their DNA. Thus, it’s used for the removal of microorganisms (2).
Matching the processes to the contaminants:
A. Aeration followed by filtration – 3. Removal of iron
B. Reverse Osmosis – 4. Removal of excess salts
C. Filtration through activated carbon – 1. Removal of colour
D. Treatment with UV light – 2. Removal of microorganism
This corresponds to the code 3 4 1 2, which is option C.

146. Villagers in some parts of India use the water extract of the ash obta

Villagers in some parts of India use the water extract of the ash obtained by burning banana plant as a substitute of soda. Which one of the following is the major active component in the extract ?

[amp_mcq option1=”Sodium Carbonate” option2=”Potassium Carbonate” option3=”Calcium Oxide” option4=”Magnesium Oxide” correct=”option2″]

This question was previously asked in
UPSC CAPF – 2009
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The major active component in the water extract of ash obtained by burning banana plants, used as a substitute for soda, is Potassium Carbonate.
Plants absorb minerals from the soil, including potassium, sodium, calcium, and magnesium. When plant material is burned, the organic components are removed, leaving behind the mineral residues, primarily as carbonates or oxides. Banana plants are known to accumulate significant amounts of potassium. Burning plant material rich in potassium leads to the formation of potassium carbonate (K₂CO₃). This alkali compound, when extracted with water, yields a solution of potassium carbonate, which has alkaline properties similar to soda (sodium carbonate or sodium bicarbonate).
Historically, wood ash was a common source of potassium carbonate (potash), used in making soap, glass, and as a leavening agent (pearl ash). Different plant species yield ash with varying compositions, but potassium is often a dominant cation in land plants.

147. Which one of the following chemicals is an artificial sweetener prescr

Which one of the following chemicals is an artificial sweetener prescribed to diabetic persons ?

[amp_mcq option1=”Aspartame” option2=”Glucose” option3=”Sucrose” option4=”Maltose” correct=”option1″]

This question was previously asked in
UPSC CAPF – 2009
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Aspartame is an artificial sweetener prescribed to diabetic persons.
Diabetic persons need to manage their blood sugar levels. Glucose, Sucrose (table sugar), and Maltose are all types of sugars that significantly increase blood sugar. Artificial sweeteners like Aspartame provide sweetness with minimal or no calories and do not raise blood sugar levels, making them suitable alternatives for diabetics.
Aspartame is a low-calorie artificial sweetener made of two amino acids, aspartic acid and phenylalanine. It is much sweeter than sugar. Other common artificial sweeteners include Saccharin, Sucralose, Stevia, and Neotame.

148. Which one among the following is an example of chemical change ?

Which one among the following is an example of chemical change ?

[amp_mcq option1=”Sublimation of camphor” option2=”Melting of ice” option3=”Heating of an iron rod” option4=”Mixing of NaOH and HCl” correct=”option4″]

This question was previously asked in
UPSC NDA-2 – 2024
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A chemical change results in the formation of new substances with different chemical properties. Mixing sodium hydroxide (NaOH, a strong base) and hydrochloric acid (HCl, a strong acid) causes a neutralization reaction: NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l). Sodium chloride (NaCl) and water (H₂O) are produced, which have entirely different chemical properties compared to the reactants. Sublimation, melting, and simple heating of a solid are physical changes, altering the state or temperature but not the chemical identity of the substance.
Chemical changes involve the breaking and forming of chemical bonds, resulting in new substances. Physical changes involve alterations in form, state, or appearance without changing chemical composition.
Neutralization reactions are a common type of chemical change where an acid and a base react to form a salt and water. These reactions are often exothermic, releasing heat.

149. The elemental composition of diamond is

The elemental composition of diamond is

[amp_mcq option1=”Carbon and Hydrogen” option2=”Carbon and Oxygen” option3=”Pure Carbon” option4=”Pure Silicon” correct=”option3″]

This question was previously asked in
UPSC NDA-2 – 2024
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Diamond is an allotrope of carbon. This means it is a form of pure carbon where the carbon atoms are arranged in a specific crystal structure (a tetrahedral lattice). Therefore, diamond consists solely of carbon atoms and no other elements. Graphite is another well-known allotrope of pure carbon.
Allotropes are different structural modifications of an element. Diamond is a crystalline allotrope of carbon.
In diamond, each carbon atom is covalently bonded to four other carbon atoms in a rigid, three-dimensional tetrahedral network. This structure makes diamond extremely hard and gives it a high melting point.

150. For Aluminium (Al) (atomic number : 13, mass number : 27), which one a

For Aluminium (Al) (atomic number : 13, mass number : 27), which one among the following statements is NOT correct ?

[amp_mcq option1=”Number of electrons present in Al is 13″ option2=”Number of protons present in Al is 13″ option3=”Number of neutrons present in Al is 14″ option4=”The valency of Al is 2″ correct=”option4″]

This question was previously asked in
UPSC NDA-2 – 2024
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For a neutral atom, the number of protons is equal to the atomic number (Z), and the number of electrons is also equal to the atomic number. Given the atomic number of Aluminium (Al) is 13, it has 13 protons and 13 electrons. The mass number (A) is the sum of protons and neutrons. Given the mass number is 27 and the number of protons is 13, the number of neutrons is 27 – 13 = 14. Aluminium is in Group 13 of the periodic table, with electronic configuration 1s² 2s² 2p⁶ 3s² 3p¹. It readily loses its 3 valence electrons to form a stable Al³⁺ ion. Therefore, the typical valency of Aluminium is 3, not 2.
Atomic number = Number of protons. For a neutral atom, Number of electrons = Number of protons. Mass number = Number of protons + Number of neutrons. Valency is related to the number of electrons an atom gains, loses, or shares to form chemical bonds.
Elements in Group 13 (like Aluminium) typically exhibit a valency of +3, forming ions with a +3 charge by losing their three valence electrons.
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