Elements And Metals Quiz 2 - General Science - Current Affairs MCQ

Explanation:
When an iron nail gets rusted, iron oxide is formed. Let's analyze the options to determine the correct answer.
A: Without any change in the weight of the nail:
This option is incorrect because when iron reacts with oxygen to form iron oxide (rust), the weight of the iron nail increases.
B: With a decrease in the weight of the nail:
This option is incorrect because, as mentioned earlier, the weight of the iron nail increases when it gets rusted. Rust is an iron oxide compound, which adds to the weight of the nail.
C: With an increase in the weight of the nail:
This option is correct because when iron reacts with oxygen to form iron oxide, the weight of the nail increases due to the addition of the iron oxide compound (rust).
D: Without any change in color or weight of the nail:
This option is incorrect because the formation of iron oxide (rust) on the iron nail changes both the color and the weight of the nail. The nail usually turns reddish-brown in color due to the presence of iron oxide.
Therefore, the correct answer is C: With an increase in the weight of the nail.

Galvanised Iron Sheets

- Galvanised iron sheets are sheets of iron or steel that have been coated with a layer of another metal to prevent rusting and corrosion.
- This process is known as galvanization.
- The coating on galvanised iron sheets provides a protective barrier between the iron or steel and the corrosive elements in the environment.
- It helps to extend the lifespan and durability of the iron sheets.

Coating of Galvanised Iron Sheets

- The coating on galvanised iron sheets is typically made of zinc.
- Zinc is a highly reactive metal that forms a protective layer of zinc oxide and zinc carbonate when exposed to the atmosphere.
- This layer acts as a barrier, preventing oxygen and moisture from reaching the iron or steel underneath.
- Zinc is chosen as the coating for galvanised iron sheets because of its excellent corrosion resistance properties.
- It sacrificially corrodes in place of the iron or steel, thereby protecting the underlying material.

Other Coating Options

- While zinc is the most common coating for galvanised iron sheets, other metals can also be used in the galvanization process.
- Lead, chromium, and tin are some examples of metals that can be used as coatings.
- However, zinc is preferred due to its cost-effectiveness, availability, and superior protective properties.

Conclusion

- Galvanised iron sheets have a coating of zinc, which provides a protective barrier against rust and corrosion.
- The zinc coating sacrificially corrodes to protect the underlying iron or steel.

Explanation:
Among the various allotropes of carbon, each has different physical properties, including hardness. The correct answer to the question is option C.
Reasoning:
- Diamond is the hardest allotrope of carbon. It has a three-dimensional network structure, with each carbon atom bonded to four neighboring carbon atoms. This strong covalent bonding gives diamond its exceptional hardness.
- Graphite, on the other hand, is the softest allotrope of carbon. It has a layered structure with strong covalent bonding within each layer but weak Van der Waals forces between the layers. These weak forces allow the layers to easily slide over each other, resulting in the characteristic softness of graphite.
- Coke, which is a form of amorphous carbon, is not as hard as diamond but not as soft as graphite. It falls between these two extremes in terms of hardness.
Therefore, the correct answer is option C: diamond is the hardest and graphite is the softest allotrope of carbon.

Explanation:
The group of metals Fe, Co, Ni can be best classified as transition metals. Here's why:
Transition Metals:
- Transition metals are located in the middle of the periodic table, between the main group elements and the inner transition metals.
- They are characterized by the presence of partially filled d orbitals in their electron configuration.
- Transition metals have similar chemical properties, including high melting and boiling points, variable oxidation states, and the ability to form complex compounds.
- Fe (iron), Co (cobalt), and Ni (nickel) all possess these characteristics, making them transition metals.
Main Group Metals:
- Main group metals are located on the left side and middle of the periodic table.
- They include elements such as sodium, aluminum, and zinc.
- Main group metals have only s and p orbitals as their valence orbitals, while transition metals have d orbitals as well.
- Fe, Co, and Ni have d orbitals, so they do not belong to the main group metals.
Alkali Metals:
- Alkali metals are located in Group 1 of the periodic table.
- They include elements such as lithium, sodium, and potassium.
- Fe, Co, and Ni do not belong to this group, so they cannot be classified as alkali metals.
Rare Metals:
- Rare metals refer to metals that are scarce or rarely found in nature.
- Fe, Co, and Ni are not considered rare metals as they are relatively abundant and widely used in various industries.
In conclusion, the most appropriate classification for Fe, Co, and Ni is transition metals, considering their electron configurations and chemical properties.

Heavy water is deuterium oxide.
Deuterium oxide, commonly known as heavy water, is a form of water that contains a higher proportion of deuterium, a heavy isotope of hydrogen. It is denoted by the chemical formula D2O. Here is a detailed explanation:
Definition of Heavy Water:
- Heavy water is a form of water in which the hydrogen atoms are replaced by deuterium, an isotope of hydrogen.
- It is called "heavy" because deuterium has an extra neutron, making it twice as heavy as normal hydrogen.
Composition:
- Heavy water has a chemical formula of D2O, indicating that it contains two deuterium atoms and one oxygen atom.
- The molecular weight of heavy water is about 20 grams per mole, compared to 18 grams per mole for regular water (H2O).
Properties of Heavy Water:
- Heavy water has a higher boiling point and freezing point compared to regular water due to its heavier isotopic composition.
- It is slightly denser than regular water.
- It has a slightly different taste compared to regular water, although this difference is very subtle.
Uses of Heavy Water:
- Heavy water is used as a moderator in nuclear reactors, where it slows down the neutrons produced during nuclear fission.
- It is also used in certain types of scientific research, such as nuclear magnetic resonance (NMR) spectroscopy.
In conclusion, heavy water is deuterium oxide, a form of water that contains a higher proportion of deuterium. It has unique properties and is used in various scientific and industrial applications.

Explanation:
To make the otherwise odorless LPG cooking gas detectable, a chemical called ethyl mercaptan is added. Ethyl mercaptan is a compound of sulfur. Here is a detailed explanation:
- LPG (liquefied petroleum gas) is a mixture of hydrocarbon gases, primarily propane and butane.
- These gases are highly flammable and have no natural smell or odor.
- In order to detect any gas leaks or potential hazards, a strong odorant is added to LPG to make it easily detectable by smell.
- Ethyl mercaptan, also known as ethanethiol, is the compound used as the odorant in LPG.
- Ethyl mercaptan is a volatile organic compound that contains sulfur.
- Sulfur compounds are known for their strong and unpleasant smell, often described as a rotten egg or skunk-like odor.
- By adding ethyl mercaptan to LPG, it imparts a distinct and easily recognizable smell to the gas, making it easily detectable in case of leaks or accidents.
Therefore, the correct answer is D: sulfur. Ethyl mercaptan is a compound of sulfur that is added to LPG cooking gas to give it a detectable smell.

The element common to all acids is hydrogen.
Explanation:
Acids are substances that release hydrogen ions (H+) when dissolved in water. This property is what makes an acid acidic. Hydrogen is the element that is responsible for the acidic properties of all acids. Here's a detailed explanation:
Properties of Acids:
- Acids have a sour taste.
- Acids turn blue litmus paper red.
- Acids react with metals to produce hydrogen gas.
- Acids conduct electricity when dissolved in water.
Role of Hydrogen:
- Hydrogen is the element that is responsible for the acidic properties of all acids.
- When an acid dissolves in water, it releases hydrogen ions (H+).
- These hydrogen ions are what make the solution acidic.
- The more hydrogen ions present, the stronger the acid.
Examples:
- Hydrochloric acid (HCl) releases hydrogen ions (H+) when dissolved in water.
- Sulfuric acid (H2SO4) also releases hydrogen ions (H+) when dissolved in water.
- Similarly, all other acids contain hydrogen and release hydrogen ions when dissolved in water.
Conclusion:
In summary, the element common to all acids is hydrogen. It is the presence of hydrogen ions (H+) that gives acids their distinctive properties.

Non-stick cooking utensils are coated with Teflon.
Explanation:
Non-stick cooking utensils have a special coating that prevents food from sticking to the surface. This coating is typically made of a material called Teflon, which is a brand name for polytetrafluoroethylene (PTFE). Here is a detailed explanation of why Teflon is used as the coating for non-stick cooking utensils:
1. Teflon's non-stick properties: Teflon has excellent non-stick properties, meaning that food is less likely to stick to its surface during cooking. This makes it easier to flip, stir, and remove food from the utensil without it sticking or breaking apart.
2. High heat resistance: Teflon is known for its high heat resistance. It can withstand temperatures up to 500°F (260°C) without degrading or releasing harmful fumes. This makes it suitable for various cooking methods, including frying, sautéing, and baking.
3. Smooth and low-friction surface: Teflon has a smooth surface with low friction, preventing food particles from adhering to the utensil. This makes it easier to clean the utensil after use, as food residues can be easily wiped off.
4. Chemical inertness: Teflon is chemically inert, meaning it does not react with food or release any harmful substances when heated. This makes it a safe choice for cooking utensils, as it does not introduce any unwanted flavors or toxins into the food.
5. Durability: Teflon coatings are highly durable and can withstand regular use for an extended period. However, it is important to note that the coating can degrade over time, especially if scratched or exposed to high heat. It is advisable to use non-metallic utensils and avoid using high heat settings to prolong the life of the Teflon coating.
In conclusion, Teflon is the preferred coating for non-stick cooking utensils due to its non-stick properties, high heat resistance, smooth surface, chemical inertness, and durability. It provides a convenient and safe cooking experience by preventing food from sticking and allowing for easy cleanup.

Monazite is an ore of Thorium
Explanation:
Monazite is a rare phosphate mineral that is an important source of thorium, a radioactive element. Here is a detailed explanation of why monazite is an ore of thorium:
1. Definition of Monazite:
Monazite is a reddish-brown phosphate mineral that contains various rare earth elements, including thorium. It has a high specific gravity and is commonly found in beach sands, alluvial deposits, and some igneous rocks.
2. Composition of Monazite:
Monazite typically contains about 12-16% thorium, making it one of the primary sources of this element. It also contains other rare earth elements like cerium, lanthanum, neodymium, and praseodymium.
3. Thorium as a Radioactive Element:
Thorium is a radioactive element that is commonly used in nuclear reactors and various industrial applications. It has a long half-life and decays into stable isotopes, releasing alpha particles during the process.
4. Extraction of Thorium from Monazite:
Monazite can be processed to extract thorium through a series of chemical and physical separation methods. These methods involve crushing, grinding, magnetic separation, and acid digestion to separate thorium from other elements present in the ore.
5. Importance of Thorium:
Thorium is a valuable resource due to its potential as a nuclear fuel in advanced nuclear reactors. It is more abundant than uranium and has several advantages, including reduced waste production and reduced risk of nuclear proliferation.
In conclusion, monazite is an ore of thorium due to its high thorium content. The extraction of thorium from monazite is important for various applications, including nuclear energy production.

Allotropes
- Carbon, diamond, and graphite are all different forms of carbon.
- These different forms of carbon are called allotropes.
- Allotropes are different structural arrangements of the same element.
- They have different physical and chemical properties.
Diamond
- Diamond is a form of carbon that has a crystal lattice structure.
- It is the hardest known natural material.
- It is transparent and has a high refractive index.
- Diamond is used in jewelry and cutting tools.
Graphite
- Graphite is a form of carbon that has a layered structure.
- It is soft and brittle.
- It is a good conductor of electricity.
- Graphite is used in pencils and as a lubricant.
Relation between Carbon, Diamond, and Graphite
- Carbon, diamond, and graphite are all made up of carbon atoms.
- The difference in their properties is due to the different arrangements of these carbon atoms.
- Diamond and graphite are both stable forms of carbon under different conditions.
- They can be interconverted under high pressure and temperature.
Significance of Allotropes
- The study of allotropes helps us understand the different behaviors and properties of elements.
- Allotropes have various applications in different fields, such as jewelry, industry, and technology.
- The unique properties of carbon allotropes make them valuable in many areas of science and technology.

Potassium Nitrate Usage:

• Fertilizer: Potassium nitrate is commonly used as a fertilizer due to its high potassium and nitrogen content. It provides essential nutrients for plant growth and helps improve crop yields.


• Gunpowder: Potassium nitrate, also known as saltpetre, is a key component of gunpowder. It is used as an oxidizing agent in the production of explosives and fireworks.


• Food Preservation: Potassium nitrate is used in certain meat curing processes to preserve the color, flavor, and texture of the meat.


• Toothpaste: In some toothpaste formulations, potassium nitrate is added to help reduce tooth sensitivity by desensitizing nerve endings in the teeth.


• Pharmaceuticals: Potassium nitrate is used in some medications, such as certain cough syrups and toothache gels, for its analgesic and anti-inflammatory properties.


• Pyrotechnics: Potassium nitrate is a crucial ingredient in the production of various pyrotechnic products, including fireworks, flares, and smoke bombs.


• Metallurgy: It is used in certain metallurgical processes, such as gold refining and heat treatment of metals.


• Heat Transfer Fluids: Potassium nitrate is used as a heat transfer medium in some solar thermal energy systems.

So, in summary, potassium nitrate is primarily used as a fertilizer, but it also finds applications in various industries such as pyrotechnics, food preservation, toothpaste, pharmaceuticals, and metallurgy.

Permanent hardness of water may be removed by the addition of sodium carbonate.
Explanation:
Water hardness is caused by the presence of calcium and magnesium ions in the water. Permanent hardness refers to the presence of calcium and magnesium sulfates and chlorides in the water, which cannot be removed by boiling.
The addition of sodium carbonate can remove permanent hardness of water due to the following reasons:
- Sodium carbonate reacts with calcium and magnesium ions in the water to form insoluble calcium carbonate and magnesium carbonate precipitates. These precipitates can be easily removed by filtration or settling.
- The chemical equation for the reaction is:
- Ca2+ + CO32- -> CaCO3 (precipitate)
- Mg2+ + CO32- -> MgCO3 (precipitate)
- Sodium carbonate acts as a precipitating agent, converting the soluble calcium and magnesium ions into insoluble carbonates.
- The precipitates formed by the reaction of sodium carbonate with calcium and magnesium ions are white in color and are responsible for the removal of permanent hardness.
- After the addition of sodium carbonate and the removal of precipitates, the water becomes soft and suitable for various household and industrial purposes.
Therefore, sodium carbonate is the correct option for removing permanent hardness of water.

The components of soda water are:
- Carbon dioxide: Soda water is carbonated water, which means it contains dissolved carbon dioxide gas. This is what gives soda water its fizziness and bubbly texture.
- Carbonic acid: When carbon dioxide dissolves in water, it forms carbonic acid. Carbonic acid is a weak acid that contributes to the slightly acidic taste of soda water.
- Sulphuric acid: Soda water does not contain sulphuric acid. It is not used in the production of soda water and would be harmful if consumed.
- Nitrous acid: Soda water does not contain nitrous acid. Nitrous acid is not used in the production of soda water and would be harmful if consumed.
So, the correct answer is option C: carbon dioxide. Soda water contains carbon dioxide, which forms carbonic acid when dissolved in water.

Bauxite is an aluminium ore and is the main source of aluminium.

Solubility in Water:
- Solubility in water refers to the ability of a substance to dissolve in water.
- Substances that are soluble in water are referred to as hydrophilic.
- Solubility is determined by the intermolecular forces between the solute and solvent molecules.
Determining the Most Soluble:
To determine the most soluble substance from the given options, we need to consider the nature of the substances and their ability to form interactions with water molecules.
Camphor:
- Camphor is sparingly soluble in water.
- Its solubility in water is about 1 g per 800 mL.
- It forms weak interactions with water molecules through hydrogen bonding.
Sulphur:
- Sulphur is insoluble in water.
- It does not form any significant interactions with water molecules.
Common Salt:
- Common salt, also known as sodium chloride (NaCl), is highly soluble in water.
- It readily dissociates into sodium ions (Na+) and chloride ions (Cl-) in water.
- These ions interact with water molecules through ion-dipole interactions, resulting in a high solubility.
Sugar:
- Sugar, also known as sucrose, is highly soluble in water.
- It readily dissolves in water due to the presence of hydroxyl groups (-OH) in its molecular structure.
- These hydroxyl groups form hydrogen bonds with water molecules, enhancing its solubility.
Conclusion:
Based on the information provided, the most soluble substance in water among the given options is sugar (option D). It exhibits a high solubility due to the presence of hydroxyl groups, which can form hydrogen bonds with water molecules. Common salt (option C) is also highly soluble in water due to the formation of ions and ion-dipole interactions.

Answer:
The correct answer is D: Helium.
The discovery of elements in the chromospheres of the sun was a significant milestone in understanding the composition of the sun and the universe. Here is a detailed explanation of the discovery order and the elements involved:
1. Helium:
- Helium was the first element to be discovered in the chromospheres of the sun.
- It was initially observed during a solar eclipse in 1868 by French astronomer Pierre Janssen and independently by English astronomer Norman Lockyer.
- They noticed a bright yellow line in the solar spectrum, which they attributed to a new element and named it helium after the Greek word "helios" meaning sun.
2. Neon:
- Neon was the second element to be discovered in the chromospheres of the sun.
- It was identified in 1898 by Scottish chemist William Ramsay and English chemist Morris Travers through their experiments with liquefied air.
- They found a new gas that emitted a distinctive reddish-orange glow when an electric current was passed through it, and they named it neon after the Greek word "neos" meaning new.
3. Krypton:
- Krypton was the third element to be discovered in the chromospheres of the sun.
- It was isolated in 1898 by Scottish chemist William Ramsay and English chemist Morris Travers.
- They discovered krypton by fractionally distilling liquid air and isolating several new gases, one of which emitted a whitish-yellow light when an electric current was passed through it. They named it krypton after the Greek word "kryptos" meaning hidden.
4. Xenon:
- Xenon was the last element to be discovered in the chromospheres of the sun.
- It was discovered in 1898 by Scottish chemist William Ramsay and English chemist Morris Travers.
- They found xenon while fractionally distilling liquid air and isolating several new gases. Xenon emitted a blue glow when an electric current was passed through it, and they named it xenon after the Greek word "xenos" meaning stranger or foreigner.
In conclusion, the correct order of discovery of elements in the chromospheres of the sun is Helium, Neon, Krypton, and Xenon.

The only liquid elements at standard temperature and pressure are bromine (Br) and mercury (Hg). Although, elements caesium (Cs), rubidium (Rb), Francium (Fr) and Gallium (Ga) become liquid at or just above room temperature.

Why sodium metal is kept under kerosene:
- Sodium is a highly reactive metal that reacts vigorously with water and air, so it needs to be stored in a medium that can prevent its contact with them. Kerosene is commonly used for this purpose.
- Kerosene is a nonpolar solvent, which means it does not readily mix with water. This property helps in creating a barrier between sodium and water, preventing any reaction from occurring.
- Kerosene also has a higher boiling point compared to water, which further helps in preventing the exposure of sodium to air and moisture.
- Another reason for using kerosene is its low reactivity with sodium. It does not react with sodium under normal conditions, ensuring the stability of the stored sodium.
- The use of kerosene as a storage medium allows sodium to be easily handled and transported without the risk of accidental reactions or explosions.
- Additionally, the use of kerosene provides a clear visual indication of the presence of sodium. Sodium stored under kerosene appears as a shiny, metallic substance, making it easily identifiable.
- It is important to note that while kerosene is a suitable medium for storing sodium, it is important to handle it with caution due to the reactivity of sodium. Safety measures should always be followed when working with sodium or any other reactive metal.

Modern admiralty gunmetal is composed of 88 percent copper, 10 percent tin, and 2 percent zinc and is used for gears and bearings that are to be subjected to heavy loads and low speeds.

Answer:
Introduction:
Radium is a radioactive element that is obtained from a specific mineral. In this response, we will discuss the mineral from which radium is obtained.
Mineral from which radium is obtained:
Radium is primarily obtained from the mineral called pitchblende. Here are some key points about pitchblende:
- Pitchblende is a type of uranium ore that contains varying amounts of radium.
- It is a dark, dense mineral that is primarily composed of uranium oxides.
- Pitchblende is found in various locations around the world, including Canada, Australia, and the Czech Republic.
How radium is extracted from pitchblende:
The extraction of radium from pitchblende involves several steps:
1. Mining: Pitchblende-containing rocks are mined from the earth's surface or underground.
2. Crushing and Grinding: The mined rocks are crushed and ground into a fine powder to increase the surface area.
3. Chemical Processing: The powdered pitchblende is treated with various chemicals, such as sulfuric acid, to dissolve the uranium and other elements.
4. Uranium Extraction: The dissolved uranium is separated from the remaining solid material through a series of chemical processes.
5. Radium Separation: Once the uranium is extracted, further chemical processes are used to isolate and purify the radium from the remaining solution.
6. Radium Production: The purified radium is then processed into various forms, such as radium chloride or radium sulfate, for different applications.
Conclusion:
Radium, a radioactive element, is obtained from the mineral called pitchblende. Pitchblende is a type of uranium ore that contains varying amounts of radium. The extraction process involves mining, crushing, chemical processing, and separation techniques to isolate and purify radium from pitchblende.