MPTET Varg 2 Science Mock Test - 2 - MPTET MCQ

Explanation:

The formula of formal charge, = V - N - B/2

Where,

V is the number of valence electrons of the neutral atom in isolation (in its ground state);

N is the number of non-bonding valence electrons on this atom in the molecule, and

B is the total number of electrons shared in bonds with other atoms in the molecule.

The atoms have been numbered as 1, 2, and 3. The formal charge on:
The central O atom marked 1:

= 6 - 2 - (6) × 1/2 = + 1

The end O atom marked 3:

= 6 - 4 - (4) × 1/2 = 0

The end O atom marked 2:

= 6 - 6 - (2) × 1/2 = - 1

Concept:

• Dietary fibres are also known as roughage.
• Roughage does not provide any nutrient to our body, but is an essential component of our food and adds to its bulk.
• This helps our body get rid of undigested food.

Explanation:

• The main sources of roughage are :
• Whole grains and pulses, potatoes, fresh fruits and vegetables.
• Milk is a good source of Calcium (mineral) required by the body.

​Important Points

• A balanced diet provides all the nutrients that our body needs, in the right quantities, along with an adequate amount of roughage and water.
• The major nutrients in our food are carbohydrates, proteins, fats, vitamins, minerals, dietary fibres and water.
•  Carbohydrates and fats mainly provide energy to our body.
•  Proteins and minerals are needed for the growth and maintenance of our body.
•  Vitamins help in protecting our body against diseases.
•  The deficiency of one or more nutrients in our food for a long time may cause certain diseases or disorders.

The correct answer is 1.2 × 108 m/s.

Key Points

CONCEPT:

• Refractive index (μ): The ratio of the velocity of light in vacuum to the velocity of light in the medium is called refractive index of that medium.

So μ = c/v

Where c is the speed of light in vacuum and v is the speed of light in the medium.

CALCULATION:

Given that:

Refractive index of the diamond (µ_d)= 2.5

We know

The velocity of light in vacuum (c) = 3 × 10⁸ m/s

To find the velocity of light in diamond (v)

Now,

Hence option 1 is correct.   

Concept:

• The coelom is a cavity present between the body wall & gut, it is lined by the mesoderm.
• Animals can be classified into three groups based on the presence or absence of the coelom.

1. Coelomates: The animals possessing the coelom i.e., the body cavity which is lined by mesoderm on all sides are called Coelomates. Eg. annelids, mollusks, arthropods, echinoderms, hemichordates, and chordates.
2. Pseudocoelomate: Animals in which the body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectoderm & endoderm. Such a body cavity is called pseudocoelom. Eg. Aschelminthes.
3. Acoelomates: Animals that do not possess the body cavity coelom are called coelomates. Eg. Platyhelminthes

​   

• Animals in which the cells are arranged in two embryonic layers, external ectoderm, and internal endoderm, are called diploblastic animals, e.g., coelenterates

Explanation:

• Adamsia or commonly called Sea anemone belongs to the class Coelenterata
• It is a diploblastic acoelomate animal i.e. body cells are arranged in two embryonic layers, external ectoderm, and internal endoderm and there is no coelom present

Important Points

General characters of phylum Coelenterata:

• Cnidarians have two distinct morphological body plans known as polyp and medusa.
• They are diploblastic and exhibit tissue grade of organization.
• The body wall is composed of an outer layer called the epidermis, an inner layer called the gastrodermis and a gelatinous mesoglea is between the outer and inner epidermis.
• They have an incomplete digestive system with only one opening.
• Cnidarians are commonly unisexual but some are bisexual. Fertilization is external.
• Asexual reproduction takes place by budding, fission, and fragmentation and they have a remarkable power of regeneration.

Concept-

• Aneuploidy is a condition that arises due to an abnormal number of chromosomes in the zygote.
• It involves the loss or gain of one chromosome.
• It is a condition of having fewer or extra chromosomes than the normal genome number of the species.
• The organisms showing aneuploidy are known as aneuploids.

Key Points

Mongoloid condition is related to trisomy.

• The errors in chromosomes occur during meiosis.
• When non-disjunction results in half of the gametes containing N+1 chromosomes and half N-1 chromosomes.
• During fertilization with normal gamete, the N+1 gamete will result in a zygote with a 2N+1 condition where a particular chromosome is present in three copies called trisomy.
• Down's syndrome in humans is due to trisomy of the 21st chromosome.

Additional Information

Monosomy 

• It is a condition in which one chromosome is devoid of its homolog.
• Turner's syndrome is the condition of monosomes in humans.

Nullisomy

• It is a condition that is deficient in a complete pair of homologous chromosomes.
• Nullisomy conditions don't survive.

Concept:

Oxidizing agent: 

• The element, atom, or ion is reduced in a redox reaction or oxidizes other elements, atoms, or ions in a chemical reaction. The oxidizing agent is also known as Oxidant.

Amphoteric:

• An amphoteric oxide is an oxide that can act as either an acid or base in a reaction to produce salt and water.
• Amphoterism depends on the oxidation states available to a chemical species.
• Because metals have multiple oxidation states, they form amphoteric oxides and hydroxides.
• Metals that display amphoterism include copper, zinc, lead, tin, beryllium, and aluminum.

Explanation: 

All oxides of lead are amphoteric in nature.

Oxidizing agents themself undergo reduction i.e. fall in oxidation number. Out of all the options only in PbO₂ oxidation state is +4, thus PbO₂ can undergo reduction only as Pb doesn't show a higher oxidation state than +4.

Hence, the correct option is (2).

Additional Information

Lead-acid battery: 

The battery uses spongy lead and lead peroxide for the conversion of chemical energy into electrical power, such type of battery is called a lead-acid battery. The lead-acid battery is most commonly used in power stations and substations because it has higher cell voltage and lower cost. It is a reversible battery.

The active elements of the lead acid are

• Lead peroxide (PbO2): It forms the positive active material; The PbO2 is dark chocolate brown in colour
• Spongy lead: It forms the negative active material; It is grey in colour.
• Dilute Sulfuric Acid (H2SO4) – It is used as an electrolyte; It contains 31% of sulfuric acid

Charging reaction:

PbO2 + H2SO4 + Pb → PbSO4 + 2H2O + PbSO4 + Electrical energy

Discharging reaction:

PbSO4 + 2H2O + PbSO4 + Electrical energy → PbO2 + H2SO4 + Pb

Reaction at the negative plate:

Pb + H2SO4 → PbSO4 + 2H+ + 2e

Reaction at the positive plate:

PbO + H2SO4 + 3H+ + 2e → 2PbSO4 + 2H2O

Hence the negative electrode in a lead-acid battery is Lead (Pb).

Concept:

Speed

• It's the distance travelled per unit of time.
• It shows, how fast an object is moving.
• It's the scalar quantity.

The formula of Speed: 

        S = d / t

where S = Speed (m/s), d = distance (m), t = time (sec)

Calculations:

Given speed = 72 km/hr 

= 72 × (5 /18) = 20 m/s

Hence, 72 km/hr = 20 m/s

Additional Information

Conversion of m/s to km/hr

• 1 m/s = 18/5 km/hr
• Comparison between Speed and Velocity

Explanation:

• Copper is a metal with a high reduction potential and a negative oxidation potential value.
• When copper reacts with hydrogen, it is positioned below it in the electrochemical series, so it does not release hydrogen gas.
• As a result, copper reacts with concentrated sulphuric acid rather than dilute sulfuric acid.
• Sulphuric acid in concentrated form is an oxidising agent.
• The reduction of H₂SO₄ produces sulphur dioxide when the copper reacts with strong sulphuric acid.
• The reaction is - 
• 
• SO₂ is a colourless gas with a choking smell.
• Hence the correct answer is SO₂, sulphur dioxide.

The correct answer is Pisum sativum.

Key Points

• Johann Gregor Mendel is considered as the Father of Genetics.
• He conducted hybridization experiments on garden peas for seven years (1856-1863) and proposed the laws of inheritance in living organisms.
• The factors, now known as genes, are responsible for transfer of characteristics from one generation to another.
• Genetics is the science which deals with the inheritance, as well as the variation of characters from parents to offspring.
• Inheritance is the process by which characters are passed on from parent to progeny; it is the basis of heredity.
• This simply means that due to inheritance, the members of the same family possess similar characteristics.
• Variation is the degree by which progeny differ from their parents or to put in simple words, it refers to the differences among individuals of the same species.

Mendel's experiment in short

• Mendel conducted artificial pollination/cross-pollination experiments using several true-breeding pea lines.
• He selected 14 true-breeding pea plant varieties, as pairs which were similar except for one character with contrasting traits like - smooth or wrinkled seeds, yellow or green seeds, inflated (full) or constricted green or yellow pods and tall or dwarf plants.
• The genetic makeup of the plant is known as the genotype. On the contrary, the physical appearance of the plant is known as phenotype.
• The genes are transferred from one generation (parent) to the another (offspring) in pairs known as allele (variant form of genes).

Explanation:

• Pisum sativum was selected by Mendel because:
  • It is an annual plant, therefore, many generations can be studied within a short period of time.
  • The pea plant can be easily grown and maintained.
  • It is a naturally self-pollinating but can also be cross-pollinated.
  • It has several contrasting characters.

Additional Information

1. Gallus gallus domesticus (Andulusian Fowl) 
   • It is one of the breeds of domestic chicken, also known as the Blue Andalusian.
   • They are either black, blue, or white-feathered.
   • The Andalusian fowl reveals the heritage of mixing.
   • The cross is made between the black and white feathers of the fowls in this breed of the Andalusian fowl. The blue feathered fowl is the product obtained from the cross.
2. Oenothera lamarkiana (Evening primerose)
   • This plant is originally native to Brazil, but has become naturalized in many countries and planted as an ornamental plant in gardens.
   • De Vries conducted experiment on Oenothera lamarckiana or Evening Primrose plant.
   • It is a self-pollinated plant and its seeds were allowed to grow, the majority of F1 plants were similar to the parents, but a few were different plants.
   • The same results were found in the F2 generation.
   • Later on, it was revealed that most of the variants isolated from Oenothera lamarckiana were due to its anomalous chromosome behaviour.
   • The chromosomes form multiple rings at meiosis and chromosomal end segments only involves in recombination (low-level crossing over) and plant shows complex heterozygosity i.e., during meiosis maternal and paternal chromosomes are arranged in alternate order.
3. Drosophila melanogaster (Fruit fly) 
   • The phenomenon of linkage was studied by the scientist T.H. Morgan using the common fruit fly or Drosophila melanogaster.
   • Linkage and recombination are phenomena that describe the inheritance of genes.
   • A linkage is a phenomenon where two or more linked genes are always inherited together in the same combination for more than two generations.
   • Morgan performed a cross between a heterozygous red-eyed female with a white-eyed male. This gave a ratio of 1:1:1:1 in the progeny (1 white eyed female, 1 red eyed female, 1 white eyed male and 1 red eyed male).
   • He performed many such crosses and came to the determination that the gene responsible for the eye color was situated on the X chromosome (one of the two sex chromosomes).

CONCEPT:

• Refraction: The bending of light or change in the direction of propagation of light as it moves from one medium to another is called refraction.

• The Snell's law or the law of refraction states that the ratio of the sine of the angle of incidence (i) to the sine of the angle of refraction (r) is constant for a light of given wavelength travelling in a given pair of media.

Where μ  = refractive index of the second medium with respect to the first medium.

EXPLANATION:

• From above it is clear that according to Snell's law,. Therefore option 2 is correct.

Science as a way of thinking involves scientific temper, scientific inquiry, and a sense of humanity, accepting that scientific ideas are tentative and control of emotions while interpreting the evidence are its important ingredients. The discussion above clearly indicates that no domain can be segregated from the other and all three are integrated.

• Critical thinking: It is the ability to analyze our experiences and review our actions through reflecting on them. It requires abstract thinking to reflect on our actions.
• Logical thinking: It requires thinking with logical reasoning. Logical thinking is the essence of having a scientific temper as it makes you focus on your observations and organize them carefully through reasoning before arriving at any conclusion.
• Objectivity: This is referred to the ability to look at things without preconceived notions, prejudices, or subjective biases. Objectivity will also help in developing respect for evidence since an objective person will only rely on unbiased evidence. Sets for a scientific inquiry with some preconceived notions in mind then there are obvious chances to obtain biased results. 
• Open-mindedness: An open-minded person listens to others and is willing to change her/his mind if warranted. Scientific temper demands that the person should be open-minded and flexible in her/his approach.
• Skepticism: It is the ability to question accepted beliefs, ideas, or facts prevalent in a society based on scientific reasoning or investigations. You should help your learners to develop this attitude of questioning widely accepted superstitions and myths in our society in the name of religion, culture, magic, and so on. It is better if you give a lot of space in your science classes about discussing such non-scientific ideas and beliefs to help learners develop into logical and rational thinkers.

Hence option 4 is correct.

The correct answer is Pressure at A < Pressure at B < Pressure at C.

Explanation:

• Pressure is the force acting on a unit area of a surface.
• Pressure = force / area on which it acts
• Liquids and gases exert pressure on the walls of their containers.
• At the same depth, the pressure inside a liquid will be equal.
• However, the liquid pressure varies with the height of the liquid. 
• The pressure of the liquid at a depth is directly proportional to the depth (P ∝ h).
• The depth at C is maximum, hence the pressure is maximum at C.
• The depth at A is minimum, hence the pressure is minimum at A.
• The above figure clearly shows, depth at A < depth at  B < depth at C.
• As a result, Pressure at A < Pressure at B < Pressure at C.

CONCEPT:

• Length is a measure of the size or distance between two points. The SI unit of length is the meter (m).
• Light year: It is the distance travelled by light in one year. 
  • A light-year is a convenient unit of measurement of large distances.
  • Generally, a light-year is used to represent astronomical distances. 
  • One light-year is approximately 9 trillion (9 × 1012) km.

EXPLANATION:

• A light-year is a unit of length. Therefore option 4 is correct.​​
• It is the distance travelled by light in a vacuum in one year.
• A light-year is used in astronomy to measure the distances of nearby stars.

⇒ 1 light-year = 1ly = 9.467 × 1015 m

Additional Information

Parsec (parallactic second):

• It is the largest practical unit of distance used in astronomy.
• It is defined as the distance at which an arc of the length of 1 astronomical unit subtends an angle of 1 second of arc.

⇒ 1 parsec = 3.08 × 1016 m

Astronomical unit:

• It is defined as the mean distance of the earth from the sun. It is used in astronomy to measure the distance of planets.

 1 astronomical unit = 1 AU = 1.496 × 1011 m

Concept:

• According to Mendel's Law of Dominance:
  • In a dissimilar pair of alleles, one allele dominates (dominant) over the other allele (recessive).
  • Thus each trait has 2 distinct phenotypic characters - one dominant and one recessive.
• However, some traits were found to be not consistent with the Law of Dominance.
• Human ABO blood grouping is one such trait which is a deviation from Mendelian laws.

Key Points

• ABO blood groups are controlled by the gene I.
• This gene is responsible for producing some sugar polymers (antigens) that are present on the surface of red blood cells.
• The kind of sugar produced is controlled by 3 alleles (instead of the usual two) - I^A, I^B and i.
• The dominant alleles I^A and I^B produce different forms of a sugar, while allele i does not produce any.
• Both I^A and I^B are dominant over allele i, but they do not suppress each other.
• This phenomenon is known as codominance.
• And since more than 2 alleles are involved, it is also an example of multiple allelism.

Explanation:

• When I^A and I^B are present together, both A and B antigens are present on the RBCs.
• This becomes the AB blood group in human beings.
• The homozygous recessive condition (ii) produces the O blood group.
• We can see the details in the table below:

Concept:

Contact  and Non-contact forces:

• The force between two bodies when they are physically in contact is called contact force.
• Examples: muscular force, frictional force, etc.
• The force between the two bodies which are not in physical contact between the two objects is called non-contact force.
• Examples: magnetic force, electrostatic force, gravitational force, etc.

Explanation :

• The force which acts on the holding bucket is due to the gravitational force.
• The force of interaction that occurs between two charges is called electrostatic charge. It is a non-contact force.
• The force applied to move a body away from us is called Push. E.g. Moving a box on a table.
• The force which results due to the action of muscles is called muscular force. E.g. walking, running, squeezing a lemon.

 So, the correct answer is : a) iii ,b) iv, c) i, d) ii.

Additional Information

• Every object in the universe, whether small or large, exerts a force on every other object, this force is known as the gravitational force. 
• The force acting on a unit area of a surface is called pressure.
• Pressure = force / area 

The correct answer is Hypermetropia.

Key Points

• Far-sightedness, also known as long-sightedness, hypermetropia, or hyperopia, is a condition of the eye where distant objects are seen clearly but near objects appear blurred.
  • This blurred effect is due to incoming light being focused behind, instead of on, the retina wall due to insufficient accommodation by the lens.
• Nearsightedness (myopia) is a common vision condition in which you can see objects near to you clearly, but objects farther away are blurry.
  • It occurs when the shape of your eye causes light rays to bend (refract) incorrectly, focusing images in front of your retina instead of on your retina.

Additional Information

• Astigmatism is a common and generally treatable imperfection in the curvature of the eye that causes blurred distance and near vision.
  • Astigmatism occurs when either the front surface of the eye (cornea) or the lens inside the eye has mismatched curves.
• Colour blindness usually involves the inability to distinguish between shades of red and green.
  • There is no treatment for inherited colour blindness.

The correct answer is: Violet, Green, Yellow, Red

CONCEPT:

Dispersion of light:

• The phenomenon in which a white light ray when falls on a prism get separated into its component colors is called dispersion of light.
• The order of colors of the rainbow is Violet, Indigo, Blue, Green, Yellow, Orange, and Red.

EXPLANATION:

The ascending order of a wavelength of seven colors is given below:  

• Violet 
• Indigo
• Blue
• Green
• Yellow
• Orange
• Red
• So, from the above sequence Violet, Green, Yellow, and Red are the correct ascending order of the wavelength of the given four colors of questions.

 Key Points

Trick to remember colors of the Spectrum of White Light - VIBGYOR 

• Here :
• V stands for violet 
• I stand for indigo
• B stands for Blue
• G stand for Green
• Y stand for Yellow
• O stand for Orange
• R stand for Red

 Additional Information

• Some examples of Dispersion of light are the formation of the rainbow, the dispersion of white light in a prism, the dispersion of light on a CD, etc.
• In rainbow formation both refraction and internal reflection take place.
• It is caused by the dispersion of sunlight by tiny water droplets, present in the atmosphere.
• These droplets act like tiny prisms.
• They refract and disperse the incident sunlight, reflect it internally, and finally refract it when it comes out of the water droplet.

Important Point

• A rainbow is always formed in the opposite direction of the Sun.

A laboratory is a place where experiments or practicals are being done. In a teaching lab, most lab work involves the preparation of solutions or arranging for equipment or specimens for practical classes and lecture cum demonstration sessions. Neither of these tasks can be done in a hurry. It is not advisable to start a practical or demonstration session without

• proper planning
• essential solutions or equipment or samples,
• the correct choice of materials or concentration of solutions etc

Key Points

The process before and after the use of laboratory equipment of science involves 

• Maintenance of seats:- Before starting any practical, it is important to check whether the seats of the lab are proper or not.
• Proper use, quantity, and type of equipment:- The types of equipment, their quantity are in proper use must be checked.
• Fire equipment- It needs to be ensured that proper safety equipment is present in the lab to avoid any mishappening.
• Laboratory equipment should always be operated in the manner recommended by the manufacturers. The technician should ensure that a copy of instruction manual is available to the users who may be students, research scholars, or academic staff.

Thus, it is concluded that all the above options are correct.

The correct answer is Electrolysis.

• Splitting water into its two components (hydrogen and oxygen) by passing a current through it, is called water electrolysis.
• Water molecules naturally disassociate into H⁺ and OH^- ions, which are pulled toward the cathode and anode, respectively.
  • At the cathode, two H+ ions pick up electrons and form H₂ gas.
  • At the anode, four OH- ions combine and release O₂ gas, molecular water, and four electrons.

Important Points

• Sublimation is the conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage.
  • Example: Snow and ice changing into water vapor in the air without first melting into water.
  • "Dry ice" is actually solid, frozen carbon dioxide, which happens to sublimate, or turn to gas, at a chilly -78.5 °C (-109.3°F).
• Fractional distillation separates a mixture into several different parts, called fractions.
  • A tall fractionating column is fitted above the mixture, with different condensers coming off at different heights.
  • The column is hot at the bottom and cools at the top.
  • Crude oil (a mixture of hydrocarbons) can be separated into different fractions using fractional distillation.
• Distillation is a procedure by which two mixed liquids with different boiling points can be separated.
  • A liquid is boiled in the "distilling flask", then the vapors travel to another section of the apparatus where they come into contact with a cool surface.
  • Distillation involves boiling a liquid, then condensing the gas and collecting the liquid elsewhere

Additional Information

• The opposite of sublimation is "deposition", where water vapor changes directly into the ice—such as snowflakes and frost.

Demonstration Method: The word demonstration means to give demos or to perform a particular activity or concept. In the demonstration method, the teaching-learning process is carried in a systematic way. Demonstration often occurs when students have a hard time connecting theories to actual practice or when students are unable to understand applications of theories.

Important Points

• The best way to teach the concept of "physical and chemical change" to class Vth students is by demonstrating the physical and chemical changes in real objects in the natural environment.

 Key Points

• The demonstration method is an activity-centered method that is being used frequently in a science classroom. 
• It is an approach in which a teacher demonstrates concepts and students learn by observing and improving understanding through visual analysis.
• The abstract concepts which are difficult to understand are brought into their concreteness and demonstrated through activities.
• The teacher shows and illustrates certain phenomenon of abstract principles through demonstrations of experiments.
• It is based on the teaching maxim "from concrete to abstract" and it includes a systematic presentation of organized series of events or equipment to a group of students for their observation.
• For example, a teacher needs to demonstrate the "three states of water" then firstly the teacher must properly plan the demonstration activity to avoid any confusion in the classroom.
• Then the organization of the required items (water, ice, and a burner to heat the water to create water vapors) should be done in order to conduct the demonstration flawlessly.

Hence, we can conclude that demonstrating the physical and chemical changes in real objects in the natural environment teaches the above concept.

Key Points

• Food chain - is a linear sequence of flow of energy takes place between different organisms that are related to each other by the food they consume.

• Food web - is an interconnection of different food chains in an ecosystem.

• Both food chains and food webs outline who eats whom in an ecosystem.
• The organisms are classified into different categories according to their feeding order.
  • Producers - synthesize food from solar energy. This covers all photosynthesizing plants and algae.
  • Primary consumers - come immediately after producers and comprise herbivores that feed on the producers directly.
  • Secondary consumers - feed on primary consumers and hence comprise of carnivores.
  • Decomposers - break down dead, decaying organisms into simpler inorganic substances. E.g. - Fungi.

Important Points

• Scavengers - are carnivorous organisms that feed on the dead and decaying flesh of an animal.
• They differ from other carnivores because they do not hunt.
• Examples - Vultures, Hyenas, Jackals, Crows.

Additional Information

• There are two main types of food chains:
  • Grazing - These food chains start with the producers and are the major system of energy flow in aquatic ecosystems.
  • Detritus - The starting point is dead organic matter from other food chains and is the major energy flow system in terrestrial ecosystems.

Correct answer: 2)

Concept:

• When magnesium strip is burnt, then ash obtained is MgO which is when dissolved in water then Mg(OH)₂ is formed.
• Mg(OH)₂ is basic in nature as it turns red litmus to blue.
• The burning magnesium ribbon in air is a direct combination reaction.
• The formation of magnesium oxide is a chemical change.

Explanation:

• The magnesium ribbon reacts with oxygen to form magnesium oxide.
• This is an example of oxidation reaction.
• Magnesium ribbon bums with a dazzling white light and produces a white powder which is magnesium oxide.
• The reaction can be represented as
• 2Mg + O₂ →2MgO

Conclusion:

Thus, when a student burns a magnesium ribbon on a bunsen flame and collects the ash formed on a watch-glass and the ribbon burns with a brilliant white light.

Concept:

• Metals are the elements with valence electrons either 1 or 2 in general.
• For example, alkali metals (sodium, potassium), and alkaline earth metals (magnesium, calcium).

Explanation:

Element X

• Element X has electronic configuration 2,8. Its atomic number becomes 10. It is neon. It has completely filled valence shell.
• It comes under the class of inert gases.
• Hence element X is a noble gas element it is neither metal nor non-metal. It's a gas.

Element Y

• Y has an electronic configuration as 2,8,7.
• Its atomic number becomes 2+8+7=17 and it is chlorine.
• It has 7 electrons in its valence shell.
• It can easily gain one electron and attain 8 electrons in its valence shell. 
• Attaining 8 electrons in the valence shell represents the stable inert gas configuration.
• For that purpose, Chlorine gains electrons. But metals lose electrons easily.
• Hence element Y is not a metal.

Element Z

• The element Z has an electronic configuration is 2,8,2.
• It has two valence electrons. Its atomic number is 12. The element is magnesium.
• It can lose those two electrons easily and becomes Mg²⁺ and attain 8 electrons in its valence shell.
• Thus, Z is a metal.

Hence, we can conclude that element Y is a non-metal and element Z is a metal. 

Concept:

Pressure:

• The force per unit area is called pressure. It is denoted by P.
• The SI unit of pressure is the pascal (Pa).
• It is a scalar quantity because the pressure acts in all directions at a point inside a gas.
• The basic formula for pressure is given by:

Explanation:

• More pressure signifies more stress. 
• If the same force is applied in a lesser area of contact, then more stress will be felt. 
• If the area of contact is increased, stress will be reduced. 
• Potters who carry heavy luggage keep cloth on the head to reduce the pressure by increasing the area of contact. 
• The correct option is to 'increase the area of contact of a load of luggage with their head.'

• Excretion is the process of removal of nitrogenous wastes from the body of an organism.
• Nitrogenous waste can be divided into three groups based on its toxicity.

1. Ammonia – animals secreting ammonia are called Ammonotelic.
2. Urea - animals secreting urea are called Ureotelic.
3. Uric acid - animals secreting uric acid are called Uricotelic.

Explanation:

• Among the given vertebrates Fishes are essentially ammonotelic
• Fishes have an aquatic habitat suitable for excreting ammonia, as it requires plenty of water for its elimination

• The other nitrogenous wastes excreted by various organisms are discussed in the following table

Additional Information

• Birds & reptiles secrete Uric acid as their main excretory product because Uric acid is a very less toxic waste and it does not require a lot of water for its elimination.
• Uric acid is excreted in the form of a semiliquid paste.
• Mammals are ureotelic in nature i.e., they excrete urea as their primary excretory substance.
• Urea is moderately water-soluble nitrogenous waste that does not require a lot of water for its elimination and can easily be excreted by mammals.

Concept:

Temperature:

• It is defined as the degree of hotness or coldness of the body.
• Temperature is a measure of the average kinetic energy of the particles in an object.
• When the temperature increases, the motion of these particles also increases.
• It is measured with a thermometer or a calorimeter. In other words, temperature determines the internal energy within a given system.

Heat and Heat flow:

• It is a form of energy that produces a sensation of warmth and flows when there is a temperature difference between two bodies.
• Heat energy can be converted to other forms of energy like kinetic energy, mechanical energy, etc.​
• Heat will flow from the high-temperature region to the low-temperature region until the temperature distribution is the same throughout the body.
• Or, there may be a temperature gradient across an object. Heat will flow so as to equalize the temperature throughout the object.

Explanation:

• When two bodies are in thermal contact, heat flow will occur between them if they differ in temperature.
• Heat will flow from the higher temperature to the lower temperature.

Additional Information
Mass:

• ​It is one of the fundamental quantities in Physics and the most basic property of matter.
• It can define mass as the measure of the amount of matter in a body.
• The SI unit of mass is Kilogram (kg).
• The mass of a body does not change at any time.
• Only for certain extreme cases when a huge amount of energy is given or taken from a body. For example: in a nuclear reaction, tiny amount of matter is converted into a huge amount of energy, this reduces the mass of the substance.

Density:

• It is defined as the mass per unit volume.
• It is inversely proportional to the volume.
• Formula, density = mass/ volume
• The SI unit of density is kg/m³.

The correct answer is 50 C

Key Points

• The rate of flow of charge between the two points in a conductor is called electric current.
• This can be mathematically represented as:
• i = 
• where, i = electric current (in Ampere), q = charge (in Coulomb), t = time (in seconds)

Calculation:

Given, i = 5A and t = 10 s and q = ?

From the formula,

 q = i ×  t

 q = 5 ×  10

 q = 50 C

 Hence 50 C is the correct answer

Concept:

Resonance:

• It can be said to be a hypothetical state of a chemical entity in which electronic structures can be represented by two or more Lewis dot structures each differing in the electronic arrangement.
• Each of the structures is called a resonating structure.
• The properties of all the resonating structures are shown by a combined form known as a resonance hybrid.

Criteria to show resonance:

• It is shown by compounds where there is the possibility of delocalization of electrons.
• Delocalisation is seen in conjugated systems where there are alternate single and double bonds present.
• Delocalisation can occur via :

  • π-π orbital overlap

  • π-σ orbital overlap

  • π-p orbital overlap
• In structures where electrons are localized, there is no possibility of resonance.
• All atoms undergoing resonance should lie on the same plane.

Explanation:-

Factors affecting the reactivity of benzene:-

• Presence of unsaturated pie-bonding.
• An alternate double bond in the ring makes it more stable.
• It has sp² hybridized carbon atoms.
• Benzene has the resonance hybrid of two structures, which makes it more reactive and stable.

Addition Reaction:-

An organic reaction in which two or more molecules combine to form a large complex product.

Benzene:

• It is a conjugated system where C - C, C = C bonds are alternatively present.
• It is also a planar molecule.

It undergoes resonance via π electron delocalization.

Thus, the presence of 3 π bonds makes it less reactive and more stable than ethene and ethyne which have a single double or triple bond.