Which of the following are sets? Justify our answer.

Question: Which of the following are sets? Justify our answer. (i)The collection of all months of a year beginning with the letter J. (ii)The collection of ten most talented writers of India. (iii)A team of eleven best-cricket batsmen of the world. (iv)The collection of all boys in your class. (v)The collection of all natural numbers less than 100. (vi)A collection of novels written by the writer Munshi Prem Chand. (vii)The collection of all even integers. (viii)The collection of questions in th...

Discuss the shape of the following molecules using the VSEPR model:

Question: Discuss the shape of the following molecules using the VSEPR model: $\mathrm{BeCl}_{2}, \mathrm{BCl}_{3}, \mathrm{SiCl}_{4}, \mathrm{ASF}_{5}, \mathrm{H}_{2} \mathrm{~S}, \mathrm{PH}_{3}$ Solution: $\mathrm{BeCl}_{2}:$ $\mathrm{Cl}: \mathrm{Be}: \mathrm{Cl}$ The central atom has no lone pair and there are two bond pairs. i.e., $\mathrm{BeCl}_{2}$ is of the type $\mathrm{AB}_{2} . \mathrm{Hence}$, it has a linear shape. $\mathrm{BCl}_{3}$ The central atom has no lone pair and there are ...

Define vital capacity. What is its significance?

Question: Define vital capacity. What is its significance? Solution: Vital capacity is the maximum volume of air that can be exhaled after a maximum inspiration. It is about 3.5 4.5 litres in the human body. It promotes the act of supplying fresh air and getting rid of foul air, thereby increasing the gaseous exchange between the tissues and the environment....

A rocket is fired ‘vertically’ from the surface of mars with a speed of 2 km s–1.

Question: A rocket is fired 'vertically' from the surface of mars with a speed of $2 \mathrm{~km} \mathrm{~s}-1$. If $20 \%$ of its initial energy is lost due to Martian atmospheric resistance, how far will the rocket go from the surface of mars before returning to it? Mass of mars $=6.4 \times 1023 \mathrm{~kg}$; radius of mars $=3395$ $\mathrm{km} ; \mathrm{G}=6.67 \times 10^{-11} \mathrm{~N} \mathrm{~m}^{2} \mathrm{~kg}^{-2}$. Solution: Initial velocity of the rocket, $v=2 \mathrm{~km} / \mat...

Write the favourable factors for the formation of ionic bond.

Question: Write the favourable factors for the formation of ionic bond. Solution: An ionic bond is formed by the transfer of one or more electrons from one atom to another. Hence, the formation of ionic bonds depends upon the ease with which neutral atoms can lose or gain electrons. Bond formation also depends upon the lattice energy of the compound formed. Hence, favourable factors for ionic bond formation are as follows: (i) Low ionization enthalpy of metal atom. (ii) High electron gain enthal...

What are the functions of liver?

Question: What are the functions of liver? Solution: Liver is the largest and heaviest internal organ of the body. It is not directly involved in digestion, but secretes digestive juices. It secretes bile which plays a major role in the emulsification of fats....

Name different types of teeth and their number in an adult human.

Question: Name different types of teeth and their number in an adult human. Solution: There are four different types of teeth in an adult human. They are as follows: (i) Incisors Theeight teeth in the front are incisors. There are four incisors each in the upper jaw and the lower jaw. They are meant for cutting. (ii)Canines The pointy teeth on either side ofthe incisors are canines. They are four in number, two each placed in the upper jaw and the lower jaw. They are meant for tearing. (iii)Prem...

Explain the term thecodont and diphyodont.

Question: Explain the term thecodont and diphyodont. Solution: Thecodont is a type of dentition in which the teeth are embedded in the deep sockets of the jaw bone. Ankylosis is absent and the roots are cylindrical. Examples include living crocodilians and mammals. Diphyodont is a type of dentition in which two successive sets of teeth are developed during the lifetime of the organism. The first set of teeth is deciduous and the other set is permanent. The deciduous set of teeth is replaced by t...

A spaceship is stationed on Mars.

Question: A spaceship is stationed on Mars. How much energy must be expended on the spaceship to launch it out of the solar system? Mass of the space ship $=1000 \mathrm{~kg}$; mass of the Sun $=2 \times 10^{30} \mathrm{~kg}$; mass of mars $=6.4 \times 10^{23} \mathrm{~kg}$; radius of mars $=3395 \mathrm{~km}$; radius of the orbit of mars $=2.28 \times 10^{8} \mathrm{~kg} ; \mathrm{G}=6.67 \times 10^{-11} \mathrm{~m}^{2} \mathrm{~kg}^{-2}$. Solution: Mass of the spaceship, $m_{\mathrm{s}}=1000 \...

Following results are observed when sodium metal is irradiated with different wavelengths.

[question] Question. Following results are observed when sodium metal is irradiated with different wavelengths. Calculate (a) threshold wavelength and, (b) Planck’s constant [/question] [solution] Solution: (a) Assuming the threshold wavelength to be $\lambda_{0} \mathrm{~nm}\left(=\lambda_{0} \times 10^{-9} \mathrm{~m}\right)$, the kinetic energy of the radiation is given as: $\mathrm{h}\left(v-v_{0}\right)=\frac{1}{2} m v^{2}$ Three different equalities can be formed by the given value as: $h ...

Define octet rule. Write its significance and limitations.

Question: Define octet rule. Write its significance and limitations. Solution: The octet rule or the electronic theory of chemical bonding was developed by Kossel and Lewis. According to this rule, atoms can combine either by transfer of valence electrons from one atom to another or by sharing their valence electrons in order to attain the nearest noble gas configuration by having an octet in their valence shell. $\ddot{o}:: c:: \ddot{0} \quad$ or $\quad \ddot{Q}=c=\ddot{0}$ The octet rule succe...

A star 2.5 times the mass of the sun and collapsed to a size of 12 km rotates with a speed of 1.2 rev. per second.

Question: A star $2.5$ times the mass of the sun and collapsed to a size of $12 \mathrm{~km}$ rotates with a speed of $1.2$ rev. per second. (Extremely compact stars of this kind are known as neutron stars. Certain stellar objects called pulsars belong to this category). Will an object placed on its equator remain stuck to its surface due to gravity? (Mass of the sun $=2 \times 10^{30} \mathrm{~kg}$ ). Solution: Yes A body gets stuck to the surface of a star if the inward gravitational force is ...

Question: Discuss the main steps in the digestion of proteins as the food passes through different parts of the alimentary canal. Solution: The digestion of proteins begins in the stomach and is completed in the small intestine. The enzymes that act on proteins are known as proteases. Digestion inthe stomach: The digestive juicesecreted in the gastric glands present on the stomach walls is called gastric juice. The main components of gastric juice are HCl, pepsinogen, and rennin. The food that e...

As you have learnt in the text,

Question: As you have learnt in the text, a geostationary satellite orbits the earth at a height of nearly $36,000 \mathrm{~km}$ from the surface of the earth. What is the potential due to earth's gravity at the site of this satellite? (Take the potential energy at infinity to be zero). Mass of the earth = $6.0 \times$ $10^{24} \mathrm{~kg}$, radius $=6400 \mathrm{~km}$. Solution: Mass of the Earth, $M=6.0 \times 10^{24} \mathrm{~kg}$ Radius of the Earth, $R=6400 \mathrm{~km}=6.4 \times 10^{6} \...

Two heavy spheres each of mass 100 kg and radius 0.10 m are placed 1.0 m apart on a horizontal table.

Question: Two heavy spheres each of mass 100 kg and radius 0.10 m are placed 1.0 m apart on a horizontal table. What is the gravitational force and potential at the mid point of the line joining the centers of the spheres? Is an object placed at that point in equilibrium? If so, is the equilibrium stable or unstable? Solution: 0; $-2.7 \times 10^{-8} \mathrm{~J} / \mathrm{kg}$ Yes; Unstable Explanation: The situation is represented in the given figure: Mass of each sphere,M= 100 kg Separation be...

Draw the Lewis structures for the following molecules and ions:

Question: Draw the Lewis structures for the following molecules and ions: $\mathrm{H}_{2} \mathrm{~S}, \mathrm{SiCl}_{4}, \mathrm{BeF}_{2}, \mathrm{CO}_{3}^{2-}, \mathrm{HCOOH}$ Solution:...

How does butter in your food gets digested and absorbed in the body?

Question: How does butter in your food gets digested andabsorbed in the body? Solution: Digestion of fats: Butter is a fat product and getsdigested in the small intestine. The bile juice secreted by the liver contains bile salts that break down large fat globules into smaller globules, so as to increase their surface area for the action of lipase. This process is referred to as emulsification of fats. After this,the pancreatic lipase present in the pancreatic juice and the intestinal lipase pres...

Two stars each of one solar mass (= 2× 1030 kg) are approaching each other for a head on collision.

Question: Two stars each of one solar mass $\left(=2 \times 10^{30} \mathrm{~kg}\right)$ are approaching each other for a head on collision. When they are a distance $109 \mathrm{~km}$, their speeds are negligible. What is the speed with which they collide? The radius of each star is $104 \mathrm{~km}$. Assume the stars to remain undistorted until they collide. (Use the known value of $G$ ). Solution: Mass of each star, $M=2 \times 10^{30} \mathrm{~kg}$ Radius of each star, $R=10^{4} \mathrm{~km...

Write Lewis symbols for the following atoms and ions:

Question: Write Lewis symbols for the following atoms and ions: $\mathrm{S}$ and $\mathrm{S}^{2-} ; \mathrm{Al}$ and $\mathrm{Al}^{3+} ; \mathrm{H}$ and $\mathrm{H}^{-}$ Solution: (i) Sand $s^{2-}$ The number of valence electrons in sulphur is 6. The Lewis dot symbol of sulphur (S) is : $\ddot{s}$ : The dinegative charge infers that there will be two electrons more in addition to the six valence electrons. Hence, the Lewis dot symbol of $S^{2-}$ is $[\because{3}:{s}]^{2-}$. (ii) $\mathrm{Al}$ an...

What would happen if HCl were not secreted in the stomach?

Question: What would happen if HCl were not secreted in the stomach? Solution: Hydrochloric acid is secreted by the glands presenton the stomach walls. It dissolves bits of food and creates an acidic medium. The acidic medium allows pepsinogen to be converted into pepsin. Pepsin plays an important role in the digestion of proteins. Therefore, if HCl were not secreted in the stomach, then pepsin would not be activated. This would affect protein digestion. A pH of about 1.8 is necessary for protei...

How are polysaccharides and disaccharides digested?

Question: How are polysaccharides and disaccharides digested? Solution: The digestion of carbohydrates takes place in the mouth andthe small intestine region of the alimentary canal. The enzymes that act on carbohydrates are collectively known as carbohydrases. Digestion inthe mouth: Asfood enters the mouth, it gets mixed with saliva. Saliva secreted by the salivary glands contains a digestive enzyme called salivary amylase. This enzyme breaks down starch into sugar at pH 6.8. StarchMaltose + Is...

A satellite orbits the earth at a height of 400 km above the surface.

Question: A satellite orbits the earth at a height of $400 \mathrm{~km}$ above the surface. How much energy must be expended to rocket the satellite out of the earth's gravitational influence? Mass of the satellite $=200 \mathrm{~kg}$; mass of the earth $=6.0 \times 10^{24} \mathrm{~kg} ;$ radius of the earth $=6.4 \times 10^{6} \mathrm{~m} ; \mathrm{G}=6.67$ $\times 10^{-11} \mathrm{~N} \mathrm{~m}^{2} \mathrm{~kg}^{-2}$. Solution: Mass of the Earth, $M=6.0 \times 10^{24} \mathrm{~kg}$ Mass of ...

Describe the digestive role of chymotrypsin. What two other digestive enzymes of the same category are secreted by its source gland?

Question: Describe the digestive role of chymotrypsin. What two other digestive enzymes of the same category are secreted by its source gland? Solution: The enzyme trypsin (present in the pancreatic juice) activates the inactive enzyme chymotrypsinogen into chymotrypsin. ChymotrypsinogenChymotrypsin (Inactive) (Active) Theactivated chymotrypsin plays an important role in the further breakdown of the partially-hydrolysed proteins. ProteinsPeptides The other digestive enzymes of the same category ...

Bile juice contains no digestive enzymes, yet it is important for digestion. Why?

Question: Bile juice contains no digestive enzymes, yet it is important for digestion. Why? Solution: Bile is a digestive juice secreted bythe liver. Although it does not contain any digestive enzymes, it plays an important role in the digestion of fats. Bile juice contains bile salts, bile pigments like bilirubin, biliverdin and phospholipids. Bile salts break down large fat globules into smaller globules so that the pancreatic enzymes can easily act on them. This process is known as emulsifica...

Bile juice contains no digestive enzymes, yet it is important for digestion. Why?

Question: Bile juice contains no digestive enzymes, yet it is important for digestion. Why? Solution: Bile is a digestive juice secreted bythe liver. Although it does not contain any digestive enzymes, it plays an important role in the digestion of fats. Bile juice contains bile salts, bile pigments like bilirubin, biliverdin and phospholipids. Bile salts break down large fat globules into smaller globules so that the pancreatic enzymes can easily act on them. This process is known as emulsifica...