Chemistry Quiz - 1, General Knowledge - Current Affairs MCQ

The nucleus of an atom consists of:


Key Points:
- The nucleus is the central part of an atom.
- It contains most of the atom's mass and is positively charged.
- The nucleus is made up of two types of particles: protons and neutrons.
Explanation:
The nucleus of an atom is the central part that contains most of its mass. It is responsible for holding the atom together. The nucleus is made up of two types of particles: protons and neutrons.
- Protons: Protons are positively charged particles found in the nucleus. They have a mass of approximately 1 atomic mass unit (amu). The number of protons in an atom determines its atomic number and defines the element.
- Neutrons: Neutrons are neutral particles found in the nucleus. They have a mass of approximately 1 amu. Together with protons, they contribute to the mass of the atom.
In summary:
- The nucleus of an atom consists of protons and neutrons.
- Electrons, which are negatively charged particles, are found outside the nucleus in orbitals.
Therefore, the correct answer is option C: protons and neutrons.

The number of moles of solute present in 1 kg of a solvent is called its molality.
Explanation:
Molality is a unit of concentration that expresses the number of moles of solute per kilogram of solvent. It is denoted by the symbol 'm'.
Here's a detailed explanation of the options given:
A: Molality - Correct Answer
- Molality is the correct answer as it specifically refers to the number of moles of solute per kilogram of solvent.
B: Molarity
- Molarity is another unit of concentration that expresses the number of moles of solute per liter of solution. It is denoted by the symbol 'M'.
C: Normality
- Normality is a unit of concentration used in acid-base reactions and expresses the number of equivalents of solute per liter of solution. It is denoted by the symbol 'N'.
D: Formality
- Formality is a rarely used unit of concentration that expresses the number of formula units of solute per liter of solution. It is denoted by the symbol 'F'.
In conclusion, the correct answer is A: molality, which represents the number of moles of solute present in 1 kg of a solvent.

The most electronegative element among the following is



Explanation:
To determine the most electronegative element among the given options, we need to compare the electronegativity values of each element. Electronegativity is a measure of an atom's ability to attract electrons towards itself in a chemical bond.
Electronegativity values:
- Sodium (Na): 0.93
- Bromine (Br): 2.96
- Fluorine (F): 3.98
- Oxygen (O): 3.44
Comparison:
- Sodium (Na) has the lowest electronegativity value among the given options.
- Bromine (Br) has a higher electronegativity value than sodium.
- Fluorine (F) has the highest electronegativity value among the given options.
- Oxygen (O) has a slightly lower electronegativity value than fluorine.
Conclusion:
From the given options, fluorine (F) has the highest electronegativity value, making it the most electronegative element among the listed choices.

Electronic configuration of Fe²⁺ is [Ar]3d⁶ 4s⁰ 
therefore, Number of electrons  = 6
Mg- 1s² 2s² 2p⁶  (6s electrons)
It matches with the 6d electrons of Fe²⁺ 
Cl- 1s² 2s² 2p⁶ 3s² 3p⁵ (11 p electrons)
It does not match with the 6d  electrons of Fe²⁺
Fe- [Ar] 3d⁶ 4s² (6d electrons)

It does not match with the 6d electrons of Fe²⁺
Ne- 1s² 2s² 2p⁶ 3s² 3p ⁶ (6p electrons)
It matches with the 6d electrons of Fe²⁺.
Hence, Cl has 11 p electrons which do not match in number with 6d electrons of Fe²⁺

The metal used to recover copper from a solution of copper sulphate is iron (Fe).
Explanation:
To recover copper from a solution of copper sulphate, a more reactive metal is required to displace the copper ions and form a solid copper metal. Iron, being more reactive than copper, can displace copper from its compound.
Here is a detailed explanation of why iron (Fe) is used to recover copper from a solution of copper sulphate:
1. Reactivity series: Metals can be arranged in an order of their reactivity. This order is known as the reactivity series. Iron is higher in the reactivity series compared to copper, which means it is more reactive than copper.
2. Redox reaction: The process of recovering copper from copper sulphate solution involves a redox reaction. In this reaction, iron acts as a reducing agent, while copper acts as an oxidizing agent.
3. Displacement reaction: Iron can displace copper from its compound, copper sulphate, by undergoing a displacement reaction. The iron atoms in the solid iron metal will replace the copper ions in the copper sulphate solution, forming solid copper metal and iron sulphate solution.
4. Formation of copper: The displaced copper ions from the copper sulphate solution will combine to form solid copper metal. This solid copper metal can be obtained by filtering or precipitating out from the solution.
In conclusion, iron (Fe) is used to recover copper from a solution of copper sulphate due to its higher reactivity, which allows it to displace copper from its compound and form solid copper metal.

The metallurgical process in which a metal is obtained in a fused state is called smelting.
Explanation:
Smelting is a process used to extract metal from its ore or raw material. It involves heating the ore to a high temperature and combining it with various reducing agents such as coke or charcoal. This process allows the metal to separate from the impurities and form a molten liquid.
Key Points:
- Smelting is a metallurgical process.
- The process involves heating the ore to a high temperature.
- Various reducing agents such as coke or charcoal are used.
- The impurities separate from the metal, which forms a molten liquid.
- Smelting is used to obtain metals in a fused state, ready for further processing and refinement.
Conclusion:
In summary, the correct answer is option A: smelting. Smelting is the process in which a metal is obtained in a fused state by heating the ore with reducing agents. This process separates the metal from impurities and forms a molten liquid, which can be further processed and refined.

Question Analysis:
The question asks which gas has the highest speed for its molecules. The given options provide different gases at different temperatures. To determine the gas with the highest speed, we need to consider the concept of kinetic theory of gases, which states that the average kinetic energy of gas particles is directly proportional to their temperature. Higher kinetic energy leads to higher molecular speed.

To determine the gas with the highest speed, we need to compare the temperatures of the gases given in the options and select the one with the highest temperature, as higher temperature implies higher molecular speed.
Option Analysis:
A: H₂ at -73^oC
- Temperature: -73^oC
B: CH₄ at 300 K
- Temperature: 300 K
C: N₂ at 1,027^oC
- Temperature: 1,027^oC
D: O₂ at 0^oC
- Temperature: 0^oC
Calculating Molecular Speed:
To compare the molecular speeds, we need to convert the temperatures to the same scale. Let's convert everything to Kelvin.
A: H₂ at -73^oC
- Temperature: -73^oC + 273.15 = 200.15 K
B: CH₄ at 300 K
- Temperature: 300 K
C: N₂ at 1,027^oC
- Temperature: 1,027^oC + 273.15 = 1,300.15 K
D: O₂ at 0^oC
- Temperature: 0^oC + 273.15 = 273.15 K
Comparing Molecular Speed:
Now that all temperatures are in Kelvin, we can compare them to determine the gas with the highest molecular speed.
A: H₂ at 200.15 K
B: CH₄ at 300 K
C: N₂ at 1,300.15 K
D: O₂ at 273.15 K
From the given options, gas C (N₂ at 1,027^oC) has the highest temperature and thus the highest molecular speed. Therefore, the answer is option C.

Explanation:
The oldest rocks in the Earth's crust were once molten and came from deep inside the Earth. These molten rocks, known as magma, were spewed out through volcanic eruptions during the early stages of the Earth's formation. As the magma reached the surface, it cooled and solidified into hard rocks.
The correct answer is:
- Option C: Igneous rocks
Details:
- Igneous rocks are formed from the solidification of molten rock material.
- Magma is the molten rock material beneath the Earth's surface, while lava is the term used for molten rock material that reaches the Earth's surface.
- Igneous rocks can have different compositions and textures depending on the cooling rate and the mineral content of the original magma.
- Granite and basalt are specific types of igneous rocks:
- Granite is a coarse-grained igneous rock that typically contains quartz, feldspar, and mica minerals.
- Basalt is a fine-grained igneous rock that is usually dark-colored and contains minerals such as pyroxene and plagioclase.
- Sedimentary rocks, on the other hand, are formed through the accumulation and compaction of sediment (e.g., sand, mud, or organic matter) over time. They are not formed directly from molten rock material like igneous rocks.
In summary, the oldest rocks in the Earth's crust were formed from molten rock called magma, which solidified into igneous rocks through volcanic eruptions. Therefore, the correct answer is option C: Igneous rocks.

Henry's Law:
- Henry's Law states that the amount of gas dissolved in a liquid is directly proportional to the partial pressure of that gas above the liquid.
- This law is named after the English chemist William Henry, who first formulated it in the early 19th century.
Explanation:
- According to Henry's Law, the solubility of a gas in a liquid is determined by the partial pressure of the gas above the liquid.
- The higher the partial pressure of the gas, the more gas molecules will dissolve in the liquid.
- Conversely, if the partial pressure of the gas decreases, the amount of gas dissolved in the liquid will also decrease.
Examples:
- Carbonation of soda: When a can of soda is opened, the partial pressure of carbon dioxide (CO2) above the liquid decreases, causing the dissolved CO2 in the soda to come out of solution in the form of bubbles.
- Oxygen transfer in the lungs: Henry's Law explains how oxygen from the air can dissolve in the liquid lining of the lungs and then diffuse into the bloodstream, where it can be transported to the body's tissues.
Importance of Henry's Law:
- Henry's Law is important in various fields, including chemistry, biology, and environmental science.
- It helps in understanding gas solubility in liquids, which has implications in processes such as gas exchange in biological systems and the dissolution of pollutants in water.
- The law is also used in practical applications such as carbonation of beverages, wastewater treatment, and the design of gas-liquid contactors in chemical engineering.
In conclusion, Henry's Law states that the amount of gas dissolved in a liquid is proportional to its partial pressure. It is a fundamental principle in understanding gas solubility and has numerous applications in various fields.

Main Buffer System of Human Blood: H2CO3 - HCO3-
The main buffer system in human blood is the bicarbonate buffer system, which consists of carbonic acid (H2CO3) and bicarbonate ion (HCO3-). This buffer system helps maintain the pH balance of blood by preventing drastic changes in acidity or alkalinity. Here's a detailed explanation of why the answer is option A:
1. Carbonic Acid (H2CO3):
- Carbonic acid is a weak acid that is formed when carbon dioxide (CO2) dissolves in water.
- It is in equilibrium with bicarbonate ion and hydrogen ion, according to the following reaction: H2CO3 ⇌ H+ + HCO3-
- Carbonic acid acts as a proton donor (acid) in the buffer system.
2. Bicarbonate Ion (HCO3-):
- Bicarbonate ion is the conjugate base of carbonic acid.
- It acts as a proton acceptor (base) in the buffer system.
- It can react with excess hydrogen ions to form carbonic acid, thus preventing a decrease in pH.
3. Function of the Buffer System:
- The bicarbonate buffer system plays a crucial role in maintaining the pH of blood within a narrow range (around 7.4).
- When excess acid is introduced into the blood, such as through the production of metabolic waste products like carbon dioxide, the buffer system helps neutralize it.
- Carbonic acid dissociates to release hydrogen ions, which are then accepted by bicarbonate ions, forming carbonic acid again.
- This reaction prevents a significant decrease in pH by removing excess hydrogen ions.
4. Importance of pH Balance in Blood:
- Maintaining the pH of blood is essential for the proper functioning of enzymes and other metabolic processes.
- Acidosis (low blood pH) or alkalosis (high blood pH) can disrupt cellular functions and lead to various health issues.
- The bicarbonate buffer system helps regulate pH and ensures the blood remains within the optimal range for normal physiological processes.
Therefore, the correct answer is option A: H2CO3 - HCO3-.

Gas Present in the Stratosphere that Filters out Ultraviolet Light:

• Ozone

Explanation:
The gas present in the stratosphere that filters out some of the sun's ultraviolet light and provides an effective shield against radiation damage to living things is ozone. Here's a detailed explanation:
1. Ozone: Ozone (O3) is a gas molecule composed of three oxygen atoms. It is formed in the stratosphere when oxygen molecules (O2) are broken down by ultraviolet (UV) light from the sun.
2. Filtering Ultraviolet Light: Ozone acts as a protective shield by absorbing most of the sun's ultraviolet-B (UV-B) and ultraviolet-C (UV-C) radiation, preventing these harmful rays from reaching the Earth's surface.
3. Importance for Living Things: Ultraviolet radiation can cause various harmful effects on living organisms, including sunburn, skin cancer, cataracts, and damage to the immune system. The presence of ozone in the stratosphere helps protect living things from these harmful effects.
4. Stratospheric Ozone Layer: The accumulation of ozone in the stratosphere forms the ozone layer, which is located approximately 10 to 50 kilometers above the Earth's surface. The ozone layer acts as a natural sunscreen for the planet.
5. Depletion of Ozone: Human activities, such as the release of chlorofluorocarbons (CFCs) and other ozone-depleting substances, have led to the thinning of the ozone layer, particularly over Antarctica (known as the ozone hole). This depletion allows more harmful UV radiation to reach the Earth's surface, leading to increased risks for living organisms.
In conclusion, ozone is the gas present in the stratosphere that filters out some of the sun's ultraviolet light, providing an effective shield against radiation damage to living things.

The most commonly used bleaching agent is chlorine.
Explanation:
- Bleaching agents are substances that are used to remove or lighten the color of materials.
- Chlorine is the most commonly used bleaching agent due to its strong oxidizing properties.
- It is widely used in various industries and applications, including water treatment, textile industry, paper industry, and household cleaning products.
- Chlorine works by breaking down the chemical bonds that give color to substances, thereby removing or lightening the color.
- It is available in various forms, such as chlorine gas, liquid chlorine, and solid chlorine compounds like sodium hypochlorite.
- Chlorine is effective in removing stains, whitening fabrics, disinfecting water, and sanitizing surfaces.
- It is important to handle chlorine with caution as it can be toxic and harmful if not used properly.
- Other bleaching agents like hydrogen peroxide and sodium chlorite are also used, but chlorine remains the most commonly used agent due to its effectiveness and availability.

The nucleus of a hydrogen atom consists of:
- 1 proton only: The nucleus of a hydrogen atom contains one proton, which has a positive charge. Protons are subatomic particles that are located in the nucleus of an atom.
- 1 proton 2 neutron: This option is incorrect because a hydrogen atom only contains one proton and no neutrons. Neutrons are subatomic particles that are also located in the nucleus of an atom but do not have a charge.
- 1 neutron only: This option is incorrect because a hydrogen atom does not contain any neutrons. Neutrons are found in the nucleus of most other atoms but not in hydrogen.
- 1 electron only: Electrons are negatively charged particles that are found outside the nucleus of an atom, in the electron cloud or energy levels. The nucleus of a hydrogen atom does not contain any electrons.
Therefore, the correct answer is option A: 1 proton only.

The heat required to raise the temperature of a body by 1 K is called Thermal Capacity.
Thermal capacity is a physical property of a body that measures its ability to store heat energy. It is commonly denoted by the symbol "C" and is measured in units of joules per Kelvin (J/K). The thermal capacity of a body depends on its mass and the specific heat capacity of the material it is made of.
Specific Heat Capacity:
Specific heat capacity is the amount of heat energy required to raise the temperature of a unit mass of a substance by 1 K (or 1 degree Celsius). It is denoted by the symbol "c" and is measured in units of joules per kilogram per Kelvin (J/kg·K). Specific heat capacity is a property of the material itself and is independent of the mass of the body.
Water Equivalent:
Water equivalent is the mass of water that would absorb the same amount of heat as the body when its temperature is raised by 1 K. It is denoted by the symbol "W" and is measured in units of kilograms (kg). Water equivalent is used to measure the heat capacity of calorimeters and other devices used in calorimetry.
Conclusion:
In conclusion, the heat required to raise the temperature of a body by 1 K is called thermal capacity. Specific heat capacity and water equivalent are related concepts but have different definitions and units of measurement.

Nuclear Particles
The nuclear particles that are assumed to hold the nucleons together are mesons. Here is a detailed explanation:
Nucleons and Nuclear Forces
- Nucleons are the particles that make up the atomic nucleus, namely protons and neutrons.
- The strong nuclear force is responsible for holding the nucleons together within the nucleus.
- This force is stronger than the electromagnetic force, which would otherwise cause the positively charged protons to repel each other.
Mesons
- Mesons are subatomic particles that are responsible for mediating the strong nuclear force.
- They are composed of a quark and an antiquark, which are particles that make up protons and neutrons.
- Mesons are considered to be the exchange particles of the strong nuclear force.
- They are responsible for transmitting the strong force between nucleons, thus keeping them bound together.
Other Options
- Electrons and positrons are not involved in holding nucleons together.
- Electrons are negatively charged particles that orbit the nucleus in electron shells, while positrons are their antimatter counterparts.
- Neutrons, although they are nucleons, do not directly contribute to the strong nuclear force.
- Neutrons mainly add stability to the nucleus through their presence, but they do not mediate the force between nucleons.
In conclusion, the nuclear particles assumed to hold the nucleons together are mesons, which mediate the strong nuclear force between nucleons within the atomic nucleus.

To find the mass of P₄O₁₀ obtained, we need to use stoichiometry, which is the relationship between the moles of reactants and products in a chemical reaction.
1. Convert the given masses of P₄ and oxygen to moles using their respective molar masses.
- Molar mass of P₄ = 4 * atomic mass of P = 4 * 31.0 g/mol = 124.0 g/mol
- Moles of P₄ = mass / molar mass = 1.33 g / 124.0 g/mol = 0.0107 mol
- Molar mass of O₂ = 2 * atomic mass of O = 2 * 16.0 g/mol = 32.0 g/mol
- Moles of O₂ = mass / molar mass = 5.07 g / 32.0 g/mol = 0.1584 mol
2. Use the balanced chemical equation to determine the stoichiometric ratio between P₄ and P₄O₁₀.
- The balanced equation for the reaction is:
P₄ + 5 O₂ → P₄O₁₀
- From the equation, we can see that 1 mole of P₄ reacts with 5 moles of O₂ to produce 1 mole of P₄O₁₀.
3. Use the stoichiometric ratio to determine the moles of P₄O₁₀ produced.
- Since the stoichiometric ratio is 1:1 between P₄ and P₄O₁₀, the moles of P₄O₁₀ produced is also 0.0107 mol.
4. Convert the moles of P₄O₁₀ to grams using its molar mass.
- Molar mass of P₄O₁₀ = 4 * atomic mass of P + 10 * atomic mass of O = 4 * 31.0 g/mol + 10 * 16.0 g/mol = 284.0 g/mol
- Mass of P₄O₁₀ = moles * molar mass = 0.0107 mol * 284.0 g/mol = 3.04 g
5. Round the calculated mass of P₄O₁₀ to the nearest hundredth.
- The mass of P₄O₁₀ obtained is 3.04 grams.
Therefore, the correct answer is B: 3.05 grams.

Explanation:
The octane number is a measure of how well a fuel resists knocking or pinging during combustion in an internal combustion engine. A higher octane number indicates better resistance to knocking. The octane number of zero is assigned to n-heptane, which is a straight-chain hydrocarbon with seven carbon atoms.
- n-heptane: n-heptane has a straight-chain structure, and it is known to have a low resistance to knocking. Therefore, it is assigned an octane number of zero.
- 2-methyl octane: This is a branched hydrocarbon with eight carbon atoms. It has a higher resistance to knocking compared to n-heptane and would have a higher octane number.
- iso-octane: Iso-octane is a branched hydrocarbon with eight carbon atoms. It is used as a reference fuel with an octane number of 100. Therefore, it would have a higher octane number than zero.
- 3-methyl octane: This is also a branched hydrocarbon with eight carbon atoms. It would have a higher octane number than n-heptane.
In summary:
The octane number of zero is assigned to n-heptane, which is option B.

The metal that is used as a catalyst in the hydrogenation of oils is Ni (nickel).
Explanation:
- Catalysts are substances that increase the rate of a chemical reaction without being consumed in the process.
- In the hydrogenation of oils, hydrogen gas is added to unsaturated fatty acids to produce saturated fatty acids.
- Nickel (Ni) is commonly used as a catalyst in this process.
- It is preferred due to its ability to activate the hydrogen gas and facilitate the addition of hydrogen to the carbon-carbon double bonds in the unsaturated fatty acids.
- Nickel catalysts are typically supported on a solid material, such as alumina, to increase their surface area and enhance their catalytic activity.
- Nickel catalysts are widely used in industrial hydrogenation processes to produce hydrogenated oils, which are often used in food processing and the production of various consumer products.
- Other metals like copper (Cu), lead (Pb), and platinum (Pt) are not commonly used as catalysts in the hydrogenation of oils.

The most abundant rare gas in the atmosphere is argon (Ar).
Explanation:
- The Earth's atmosphere consists of several gases, including nitrogen (N2), oxygen (O2), carbon dioxide (CO2), and smaller amounts of other gases.
- Among these gases, the rare gases, also known as noble gases, are present in trace amounts.
- The rare gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).
- Out of these rare gases, argon (Ar) is the most abundant in the Earth's atmosphere, accounting for about 0.934% of the total volume.
- Here is a breakdown of the relative abundance of rare gases in the atmosphere:
- Argon (Ar): 0.934%
- Neon (Ne): 0.0018%
- Helium (He): 0.0005%
- Krypton (Kr): 0.0001%
- Xenon (Xe): 0.0000087%
- Radon (Rn): Trace amounts
- It is important to note that although argon is the most abundant rare gas, it is still considered a trace gas in the atmosphere.
- Argon is chemically inert and does not readily react with other elements, making it a stable component of the Earth's atmosphere.
- It is primarily generated through the radioactive decay of potassium-40 in rocks and soils.
- Argon is widely used in various applications, including as a protective gas in welding, as a component in incandescent light bulbs, and in scientific research.

Explanation:
The Latin word formica means ant. The name formic acid is derived from this Latin word because:
C: This acid was first obtained by the distillation of ants.
- Formic acid was first discovered by the distillation of ants, specifically red ants, by the French chemist Louis Pasteur in 1671.
- The acid was obtained by crushing and distilling the ants, resulting in the isolation of formic acid.
- The word "formic" is derived from the Latin word "formica," which means ant.
- Therefore, the name "formic acid" was given to this acid because it was initially obtained from ants.
It is important to note that the other options are not correct:
- Option A: Formic acid was not used in ancient times to eliminate ant-hills.
- Option B: Formic acid is not secreted by ants to drive away their enemies.
- Option D: Ants are not attracted by the odor of formic acid.
Overall, the name "formic acid" is derived from the Latin word "formica" because it was first obtained by the distillation of ants.

The ore found in abundance in India is monazite.
Monazite is a rare-earth phosphate mineral that contains a high concentration of rare-earth elements. It is typically found in beach sand deposits, particularly along the coastlines of Odisha, Andhra Pradesh, Tamil Nadu, and Kerala in India. Here is a detailed explanation of why monazite is the abundant ore in India:
1. Abundance:
- India has one of the world's largest reserves of monazite, estimated at around 12 million tonnes. This makes it a significant source of rare-earth elements.
- Monazite deposits are primarily found in placer deposits, which are formed by the accumulation of heavy minerals in beach sands over millions of years.
2. Rare-earth elements:
- Monazite is rich in rare-earth elements such as cerium, lanthanum, neodymium, and thorium.
- These elements have various industrial applications, including the production of magnets, catalysts, ceramics, and electronics.
3. Strategic importance:
- Rare-earth elements are considered strategically important due to their use in advanced technologies like electric vehicles, wind turbines, and smartphones.
- India's abundance of monazite provides a domestic supply of rare-earth elements, reducing dependence on imports.
4. Government regulations:
- The Indian government has imposed restrictions on the export of monazite to ensure the availability of rare-earth elements for domestic industries.
- This policy aims to promote value addition and the development of a domestic rare-earth industry.
In conclusion, monazite is the ore found in abundance in India. Its high concentration of rare-earth elements and the country's large reserves make it strategically important for domestic industries. The government's regulations on monazite export further emphasize its significance in India's resource landscape.

The inherited traits of an organism are controlled by DNA molecules.
Explanation:
- DNA (deoxyribonucleic acid) is a molecule that carries genetic information in all living organisms.
- DNA is made up of nucleotides, which are the building blocks of DNA.
- The sequence of nucleotides within a DNA molecule determines the genetic code and ultimately controls the inherited traits of an organism.
- The genetic information encoded in DNA is passed from parents to offspring through the process of reproduction.
- During reproduction, DNA is replicated and passed on to the next generation, ensuring the transmission of genetic traits.
- The inherited traits of an organism, such as eye color, height, and susceptibility to certain diseases, are determined by specific genes located on the DNA molecule.
- Genes are segments of DNA that contain the instructions for making proteins, which are responsible for various traits and functions in an organism.
- Through the process of gene expression, the information stored in DNA is used to produce proteins, which ultimately influence the development and characteristics of an organism.
- Therefore, DNA molecules play a crucial role in controlling the inherited traits of an organism.

The heat energy produced when the human body metabolizes 1 gram of fat can be calculated using the energy content of fat and the efficiency of metabolism.
1. Energy content of fat:
- Fat contains approximately 9 kilocalories (kcal) or 37.7 kilojoules (kJ) of energy per gram.
2. Efficiency of metabolism:
- The efficiency of metabolism refers to the percentage of energy that is converted into heat during metabolism. In the case of fat metabolism, the efficiency is around 40%.
3. Calculation:
To calculate the heat energy produced when the human body metabolizes 1 gram of fat, we can use the following formula:
Heat energy = Energy content of fat x Efficiency of metabolism
Substituting the values:
Heat energy = 37.7 kJ x 0.40
Heat energy = 15.08 kJ
Therefore, the correct answer is C: 39 KJ.

One mole of CO2 has mass of 44 g and 32 g of O2. So 16 g of O2 have 22 g of CO2 or 0.5 moles of it.

Newlands, Mendeleev, and Meyer
- These three scientists are associated with the development of the periodic table of elements.
- Each scientist made significant contributions to the understanding and organization of the elements.
- Let's look at each scientist's contributions individually:
John Newlands:
- Newlands proposed the Law of Octaves in 1864.
- According to this law, elements exhibit similar properties when arranged in order of increasing atomic weight.
- Newlands noticed that every eighth element had similar properties, similar to the musical octaves.
- Although Newlands' law had limitations, it laid the foundation for the periodic table.
Dmitri Mendeleev:
- Mendeleev is widely known as the father of the periodic table.
- In 1869, he published the first widely recognized version of the periodic table.
- Mendeleev organized the elements based on their atomic weight and properties.
- He left gaps in the table for undiscovered elements and predicted their properties.
- Mendeleev's periodic table provided a systematic arrangement of elements and became the basis for further developments.
Julius Lothar Meyer:
- Meyer independently developed a periodic table around the same time as Mendeleev.
- He also arranged the elements based on their atomic weights and properties.
- Meyer's table was similar to Mendeleev's but differed in some details.
- Although Meyer's work was not as widely recognized as Mendeleev's, he made significant contributions to the development of the periodic table.
Conclusion:
- Newlands, Mendeleev, and Meyer played crucial roles in the development of the periodic table of elements.
- Their contributions laid the foundation for the systematic organization of elements based on their properties and atomic weights.