Differentiate between
Question: Differentiate between (a) Respiration and Combustion (b) Glycolysis and Krebs cycle (c) Aerobic respiration and Fermentation Solution: (a)Respiration and combustion (b)Glycolysis and Krebs cycle (c)Aerobic respiration and fermentation...
Read More →Describe the theory associated with the radius of an atom as it
Question: Describe the theory associated with the radius of an atom as it (a) gains an electron (b) loses an electron Solution: (a) When an atom gains an electron, its size increases. When an electron is added, the number of electrons goes up by one. This results in an increase in repulsion among the electrons. However, the number of protons remains the same. As a result, the effective nuclear charge of the atom decreases and the radius of the atom increases. (b)When an atom loses an electron, t...
Read More →How would you react to the statement that the electronegativity
Question: How would you react to the statement that the electronegativity of N on Pauling scale is 3.0 in all the nitrogen compounds? Solution: Electronegativity of an element is a variable property. It is different in different compounds. Hence, the statement which says that the electronegativity of $N$ on Pauling scale is $3.0$ in all nitrogen compounds is incorrect. The electronegativity of $\mathrm{N}$ is different in $\mathrm{NH}_{3}$ and $\mathrm{NO}_{2}$....
Read More →What is the basic difference between the terms electron gain enthalpy and electronegativity?
Question: What is the basic difference between the terms electron gain enthalpy and electronegativity? Solution: Electron gain enthalpy is the measure of the tendency of an isolated gaseous atom to accept an electron, whereas electronegativity is the measure of the tendency of an atom in a chemical compound to attract a shared pair of electrons....
Read More →Separation of Motion of a system of particles into motion of the centre of mass and motion about the centre of mass:
Question: Separation of Motion of a system of particles into motion of the centre of mass and motion about the centre of mass: (a) Showpi=pi+miV Where $\mathbf{p}_{i}$ is the momentum of the $i^{\text {th }}$ particle (of mass $m_{i}$ ) and $\mathbf{p}_{i}{ }^{\prime}=m_{i} \mathbf{v}^{\prime}{ }_{i}$. Note $\mathbf{v}^{\prime}{ }_{i}$ is the velocity of the $i^{\text {th }}$ particle relative to the centre of mass. Also, prove using the definition of the centre of mass $\sum \mathbf{p}^{\prime}...
Read More →Distinguish cytokinesis from karyokinesis.
[question] Question. Distinguish cytokinesis from karyokinesis. [/question] [solution] Solution: [/solution]...
Read More →Would you expect the second electron gain enthalpy of O as positive, more negative or less negative than the first?
Question: Would you expect the second electron gain enthalpy of O as positive, more negative or less negative than the first?Justify your answer. Solution: When an electron is added to O atom to form Oion, energy is released. Thus, the first electron gain enthalpy of O is negative. $\mathrm{O}_{(g)}+\mathrm{e}^{-} \longrightarrow \mathrm{O}_{(g)}^{-}$ On the other hand, when an electron is added to $\mathrm{O}^{-}$ion to form $\mathrm{O}^{2-}$ ion, energy has to be given out in order to overcome...
Read More →Which of the following pairs of elements would have a more negative electron gain enthalpy?
Question: Which of the following pairs of elements would have a more negative electron gain enthalpy? (i) $\mathrm{O}$ or $\mathrm{F}$ (ii) $\mathrm{F}$ or $\mathrm{Cl}$ Solution: (i)O and F are present in the same period of the periodic table. An F atom has one proton and one electron more than O and as an electron is being added to the same shell, the atomic size of F is smaller than that of O. As F contains one proton more than O, its nucleus can attract the incoming electron more strongly in...
Read More →If $\tan (\mathrm{A}+\mathrm{B})=\sqrt{3}$
[question] Question. If $\tan (\mathrm{A}+\mathrm{B})=\sqrt{3}$ and $\tan (\mathrm{A}-\mathrm{B})=\frac{\mathbf{1}}{\sqrt{\mathbf{3}}}$ $0^{\circ}\mathrm{B}$, find $\mathrm{A}$ and $\mathrm{B}$. [/question] [solution] Solution: $\tan (\mathrm{A}+\mathrm{B})=\sqrt{\mathbf{3}} \quad \Rightarrow \mathrm{A}+\mathrm{B}=60^{\circ}$ ...(1) $\tan (\mathrm{A}-\mathrm{B})=\frac{1}{\sqrt{3}} \quad \Rightarrow \mathrm{A}-\mathrm{B}=30^{\circ}$ ...(2) Adding (1) and (2), $2 \mathrm{~A}=90^{\circ} \Rightarrow...
Read More →What is the average cell cycle span for a mammalian cell?
[question] Question. What is the average cell cycle span for a mammalian cell? [/question] [solution] Solution: The average cell cycle span for a mammalian cell is approximately 24 hours. [/solution]...
Read More →Read each statement below carefully, and state, with reasons, if it is true or false;
Question: Read each statement below carefully, and state, with reasons, if it is true or false; (a) During rolling, the force of friction acts in the same direction as the direction of motion of the CM of the body. (b) The instantaneous speed of the point of contact during rolling is zero. (c) The instantaneous acceleration of the point of contact during rolling is zero. (d) For perfect rolling motion, work done against friction is zero. (e) A wheel moving down a perfectlyfrictionlessinclined pl...
Read More →The first ionization enthalpy values (in kJmol–1) of group 13 elements are :
Question: The first ionization enthalpy values (in $\mathrm{kJmol}^{-1}$ ) of group 13 elements are How would you explain this deviation from the general trend? Solution: On moving down a group, ionization enthalpy generally decreases due to an increase in the atomic size and shielding. Thus, on moving down group 13, ionization enthalpy decreases from B to Al. But, Ga has higher ionization enthalpy than Al. Al follows immediately aftersblock elements, whereas Ga follows afterdblock elements. The...
Read More →The first ionization enthalpy values (in kJmol–1) of group 13 elements are :
Question: The first ionization enthalpy values (in $\mathrm{kJmol}^{-1}$ ) of group 13 elements are How would you explain this deviation from the general trend? Solution: On moving down a group, ionization enthalpy generally decreases due to an increase in the atomic size and shielding. Thus, on moving down group 13, ionization enthalpy decreases from B to Al. But, Ga has higher ionization enthalpy than Al. Al follows immediately aftersblock elements, whereas Ga follows afterdblock elements. The...
Read More →What are the various factors due to which the ionization enthalpy of the main
Question: What are the various factors due to which the ionization enthalpy of the main group elements tends to decrease down a group? Solution: The factors responsible for the ionization enthalpy of the main group elements to decrease down a group are listed below: (i)Increase in the atomic size of elements: As we move down a group, the number of shells increases. As a result, the atomic size also increases gradually on moving down a group. As the distance of the valence electrons from the nucl...
Read More →A cylinder of mass 10 kg and radius 15 cm is rolling perfectly on a plane of inclination 30°.
Question: Acylinder of mass $10 \mathrm{~kg}$ and radius $15 \mathrm{~cm}$ is rolling perfectly on a plane of inclination $30^{\circ}$. The coefficient of static friction $\mu_{\mathrm{s}}=0.25$. (a) How much is the force of friction acting on the cylinder? (b) What is the work done against friction during rolling? (c) If the inclinationof the plane is increased, at what value ofdoes the cylinder begin to skid, and not roll perfectly? Solution: Mass of the cylinder,m= 10 kg Radius of the cylinde...
Read More →Give the location of the centre of mass of a
[question] Question. Give the location of the centre of mass of a (i) sphere, (ii) cylinder, (iii) ring, (iv) cube, each of uniform mass density. Does the centre of mass of a body necessarily lie inside the body? [/question] [solution] solution: Geometric centre; No The centre of mass (C.M.) is a point where the mass of a body is supposed to be concentrated. For the given geometric shapes having a uniform mass density, the C.M. lies at their respective geometric centres. The centre of mass of a ...
Read More →Choose the correct option and justify your choice:
[question] Question. Choose the correct option and justify your choice: (i) $\frac{2 \tan 30^{\circ}}{1+\tan ^{2} 30^{\circ}}=$ (A) sin 60° (B) cos 60° (C) tan 60° (D) sin 30° (ii) $\frac{1-\tan ^{2} 45^{\circ}}{1+\tan ^{2} 45^{\circ}}=$ (A) tan 90° (B) 1 (C) sin 45° (D) 0 (iii) $\sin 2 \mathrm{~A}=2 \sin \mathrm{A}$ is true when $\mathrm{A}=$ (A) 0° (B) 30° (C) 45° (D) 60° (iv) $\frac{2 \tan 30^{\circ}}{1-\tan ^{2} 30^{\circ}}=$ (A) cos 60° (B) sin 60 (C) tan 60° (D) sin 30° [/question] [soluti...
Read More →How would you explain the fact that the first ionization enthalpy of sodium is
Question: How would you explain the fact that the first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium? Solution: The first ionization enthalpy of sodium is lower than that of magnesium. This is primarily because of two reasons 1. The atomic size of sodium is greater than that of magnesium 2. The effective nuclear charge of magnesium is higher than that of sodium For these reasons, the energy required to remove an...
Read More →Give comparison between the following:
Question: Give comparison between the following: (a)C3and C4pathways (b)Cyclic and non-cyclic photophosphorylation (c)Anatomy of leaf in C3and C4plants Solution: (a)C3and C4pathways (b)Cyclic and non-cyclic photophosphorylations (c)Anatomy of the leaves in C3and C4 plants...
Read More →A solid disc and a ring, both of radius 10 cm are placed on a horizontal table simultaneously,
Question: A solid disc and a ring, both of radius $10 \mathrm{~cm}$ are placed on a horizontal table simultaneously, with initial angular speed equal to $10 \pi$ rad $\mathrm{s}^{-1}$. Which of the two will start to roll earlier? The co-efficient of kinetic friction is $\mu_{\mathrm{k}}=0.2$. Solution: Disc Radii of the ring and the disc,r= 10 cm = 0.1 m Initial angular speed, $\omega_{0}=10 \pi \mathrm{rad} \mathrm{s}^{-1}$ Coefficient of kinetic friction, $\mu_{\mathrm{k}}=0.2$ Initial velocit...
Read More →Among the second period elements the actual ionization enthalpies are in the
Question: Among the second period elements the actual ionization enthalpies are in the order $\mathrm{Li}\mathrm{B}\mathrm{Be}\mathrm{C}\mathrm{O}\mathrm{N}\mathrm{F}\mathrm{Ne} .$ Explain why (i) Be has higher $\Delta_{i} H$ than B (ii) $\mathrm{O}$ has lower $\Delta_{i} H$ than $\mathrm{N}$ and $\mathrm{F}$ ? Solution: (i) During the process of ionization, the electron to be removed from beryllium atom is a $2 s$-electron, whereas the electron to be removed from boron atom is a $2 p$-electron....
Read More →Figure 13.10 shows the effect of light on the rate of photosynthesis. Based on the graph, answer the following questions:
Question: Figure 13.10 shows the effect of light on the rate of photosynthesis. Based on the graph, answer the following questions: (a)At which point/s (A, B or C) in the curve is light a limiting factor? (b)What could be the limiting factor/s in region A? (c)What do C and D represent on the curve? Solution: (a)Generally, light is not a limiting factor. It becomes a limiting factor for plants growing in shade or under tree canopies. In the given graph, light is a limiting factor at the point whe...
Read More →Describe the important properties of enzymes.
[question] Question. Describe the important properties of enzymes. [/question] [solution] Solution: Properties of enzymes (1) Enzymes are complex macromolecules with high molecular weight. (2) They catalyze biochemical reactions in a cell. They help in the breakdown of large molecules into smaller molecules or bring together two smaller molecules to form a larger molecule. (3) Enzymes do not start a reaction. However, they help in accelerating it. (4) Enzymes affect the rate of biochemical react...
Read More →Look at leaves of the same plant on the shady side and compare it with the leaves on the sunny side.
Question: Look at leaves of the same plant on the shady side and compare it with the leaves on the sunny side. Or, compare the potted plants kept in the sunlight with those in the shade. Which of them has leaves that are darker green? Why? Solution: Light is a limiting factor for photosynthesis. Leaves get lesser light for photosynthesis when they are in shade. Therefore, the leaves or plants in shade perform lesser photosynthesis as compared to the leaves or plants kept in sunlight. In order to...
Read More →Evaluate :
[question] Question. Evaluate : (i) $\sin 60^{\circ} \cos 30^{\circ}+\sin 30^{\circ} \cos 60^{\circ}$ (ii) $2 \tan ^{2} 45^{\circ}+\cos ^{2} 30^{\circ}-\sin ^{2} 60^{\circ}$ (iii) $\frac{\cos 45^{\circ}}{\sec 30^{\circ}+\operatorname{cosec} 30^{\circ}}$ (iv) $\frac{\sin 30^{\circ}+\tan 45^{\circ}-\operatorname{cosec} 60^{\circ}}{\sec 30^{\circ}+\cos 60^{\circ}+\cot 45^{\circ}}$ (v) $\frac{5 \cos ^{2} 60^{\circ}+4 \sec ^{2} 30^{\circ}-\tan ^{2} 45^{\circ}}{\sin ^{2} 30^{\circ}+\cos ^{2} 30^{\circ...
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