Can you attempt building models of biomolecules using
[question] Question. Can you attempt building models of biomolecules using commercially available atomic models (Ball and Stick models). [/question] [solution] Solution: Ball and stick models are 3-D molecular models that can be used to describe the structure of biomolecules. In ball and stick model, the atoms are represented as balls whereas the bonds that hold the atoms are represented by the sticks. Double and triple bonds are represented by springs that form curved connections between the ba...
Read More →(a) How many sub-shells are associated with n = 4?
Question: (a) How many sub-shells are associated withn= 4? (b) How many electrons will be present in the sub-shells having $m_{s}$ value of $-1 / 2$ for $n=4 ?$ Solution: (a) $n=4$ (Given) For a given value of ' $n$ ', ' $r$ can have values from zero to $(n-1)$. $\therefore I=0,1,2,3$ Thus, four sub-shells are associated withn= 4, which ares,p,dandf. (b) Number of orbitals in the $n^{\text {th }}$ shell $=n^{2}$ For $n=4$ Number of orbitals = 16 If each orbital is taken fully, then it will have ...
Read More →What causes the opening and closing of guard cells of stomata during transpiration?
Question: What causes the opening and closing of guard cells of stomata during transpiration? Solution: The tiny pores present on the surfaces of leaves, called stomata, help in the exchange of gases. Each stoma consists of bean-shaped or dumbbell-shaped guard cells. The epidermal cells surrounding the guard cells are modified to form subsidiary cells. The opening and closing of the guard cells is caused by a change in their turgidity. The inner walls of the guard cells are thick and elastic, wh...
Read More →If $3 \cot \mathrm{A}=4$, check whether
[question] Question. If $3 \cot \mathrm{A}=4$, check whether $\frac{1-\tan ^{2} \mathbf{A}}{1+\tan ^{2} \mathbf{A}}=\cos ^{2} \mathrm{~A}-\sin ^{2} \mathrm{~A}$ or not. [/question] [solution] Solution: In figure, $3 \cot A=4$ $\Rightarrow \cot A=\frac{4}{3}$ $\Rightarrow \frac{A B}{B C}=\frac{4}{3}$ $\Rightarrow \mathrm{AB}=4 \mathrm{k}$ and $\mathrm{BC}=3 \mathrm{k}$ Then $\sin \mathrm{A}=\frac{\mathbf{B C}}{\mathbf{A C}}=\frac{\mathbf{3 k}}{\mathbf{5 k}}=\frac{\mathbf{3}}{\mathbf{5}}$, $\cos A...
Read More →A man stands on a rotating platform,
Question: A man stands on a rotating platform, with his arms stretched horizontally holding a $5 \mathrm{~kg}$ weight in each hand. The angular speed of the platform is 30 revolutions per minute. The man then brings his arms close to his body with the distance of each weight from the axis changing from $90 \mathrm{~cm}$ to $20 \mathrm{~cm}$. The moment of inertia of the man together with the platform may be taken to be constant and equal to $7.6 \mathrm{~kg} \mathrm{~m}^{2}$. (a) What is his new...
Read More →What causes the opening and closing of guard cells of stomata during transpiration?
Question: What causes the opening and closing of guard cells of stomata during transpiration? Solution: The tiny pores present on the surfaces of leaves, called stomata, help in the exchange of gases. Each stoma consists of bean-shaped or dumbbell-shaped guard cells. The epidermal cells surrounding the guard cells are modified to form subsidiary cells. The opening and closing of the guard cells is caused by a change in their turgidity. The inner walls of the guard cells are thick and elastic, wh...
Read More →Can you describe what happens when milk is converted
[question] Question. Can you describe what happens when milk is converted into curd or yoghurt from your understanding of proteins. [/question] [solution] Solution: Proteins are macromolecules formed by the polymerization of amino acids. Structurally, proteins are divided into four levels. (a) Primary structure – It is the linear sequence of amino acids in a polypeptide chain. (b) Secondary structure – The polypeptide chain is coiled to form a three-dimensional structure. (c) Tertiary structure ...
Read More →Explain pressure flow hypothesis of translocation of sugars in plants.
Question: Explain pressure flow hypothesis of translocation of sugars in plants. Solution: According to the pressure flow hypothesis, food is prepared in the plant leaves in the form of glucose. Before moving into the source cells present in the phloem, the prepared food is converted into sucrose. Water moves from the xylem vessels into the adjacent phloem, thereby increasing the hydrostatic pressure in the phloem. Consequently, the sucrose moves through the sieve cells of the phloem. The sucros...
Read More →Explain why xylem transport is unidirectional and phloem transport bi-directional.
Question: Explain why xylem transport is unidirectional and phloem transport bi-directional. Solution: During the growth of a plant, its leaves act as the source of food as they carry out photosynthesis. The phloem conducts the food from the source to the sink (the part of the plant requiring or storing food). During spring, this process is reversed as the food stored in the sink is mobilised toward the growing buds of the plant, through the phloem. Thus, the movement of food in the phloem is bi...
Read More →What essential role does the root endodermis play during mineral absorption in plants?
Question: What essential role does the root endodermis play during mineral absorption in plants? Solution: In plants, nutrients are absorbed through the active and passive transports. The endodermal cells of the roots containing suberin allow only selected minerals to pass through them. The transport proteins present in the membranes of these cells act as check points for the various solutes reaching the xylem....
Read More →As shown in Fig.7.40, the two sides of a step ladder BA and CA are 1.6 m long and hinged at A.
Question: As shown in Fig.7.40, the two sides of a step ladder BA and CA are $1.6 \mathrm{~m}$ long and hinged at A A rope DE, $0.5 \mathrm{~m}$ is tied half way up. A weight $40 \mathrm{~kg}$ is suspended from a point $F, 1.2 \mathrm{~m}$ from $B$ along the ladder BA. Assuming the floor to be frictionless and neglecting the weight of the ladder, find the tension in the rope and forces exerted by the floor on the ladder. (Take $g=9.8 \mathrm{~m} / \mathrm{s}^{2}$ ) (Hint: Consider the equilibriu...
Read More →Explain the composition of triglyceride.
[question] Question. Explain the composition of triglyceride. [/question] [solution] Solution: Triglyceride is a glyceride, which is formed from a single molecule of glycerol, esterified with three fatty acids. It is mainly present in vegetable oils and animal fat. Structure of triglyceride The general chemical formula of triglyceride is $\mathrm{R}_{2} \mathrm{COO}-\mathrm{CH}_{2} \mathrm{CH}\left(-\mathrm{OOCR}_{1}\right) \mathrm{CH}_{2}-\mathrm{OOCR}_{3}$, where $\mathrm{R}_{1}, \mathrm{R}_{2...
Read More →Indicate the number of unpaired electrons in:
Question: Indicate the number of unpaired electrons in: (a) $\mathrm{P}$, (b) $\mathrm{Si}$, (c) $\mathrm{Cr}$, (d) Fe and (e) $\mathrm{Kr}$. Solution: (a) Phosphorus (P): Atomic number $=15$ The electronic configuration of $P$ is: $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{3}$ The orbital picture of $P$ can be represented as: From the orbital picture, phosphorus hasthreeunpaired electrons. (b) Silicon (Si): Atomic number = 14 The electronic configuration of Si is: $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 ...
Read More →Discuss the factors responsible for ascent of xylem sap in plants.
Question: Discuss the factors responsible for ascent of xylem sap in plants. Solution: Transpirational pull is responsible for the ascent of water in the xylem. This ascent of water is dependent on the following physical factors: Cohesion Mutual attraction between water molecules Surface tension Responsible for the greater attraction between water molecules in liquid phase than in gaseous phase Adhesion Attraction of water molecules to polar surfaces Capillarity Ability of water to rise in thin ...
Read More →Find out and make a list of proteins used as therapeutic agents.
[question] Question. Find out and make a list of proteins used as therapeutic agents. Find other applications of proteins (e.g., cosmetics, etc.) [/question] [solution] Solution: Proteins used as therapeutic agents are as follows: 1. Thrombin and fibrinogen – They help in blood clotting. 2. Antigen (antibody) – It helps in blood transfusion. 3. Insulin – It helps in maintaining blood glucose level in the body. 4. Renin – It helps in osmoregulation. Proteins are also commonly used in the manufact...
Read More →If $\cot \theta=\frac{7}{8}$, evaluate :
[question] Question. If $\cot \theta=\frac{7}{8}$, evaluate : (i) $\frac{(\mathbf{1}+\sin \theta)(\mathbf{1}-\sin \theta)}{\mathbf{( 1}+\cos \theta)(\mathbf{1}-\cos \theta)}$ (ii) $\cot ^{2} \theta$ [/question] [solution] Solution: In figure, $\cot \theta=\frac{\mathbf{7}}{\mathbf{8}}$ $\Rightarrow \quad \frac{\mathbf{A B}}{\mathbf{B C}}=\frac{\mathbf{7}}{\mathbf{8}}$ $\Rightarrow \quad \mathrm{AB}=7 \mathrm{k}$ and $B C=8 \mathrm{k}$ Now, $A C^{2}=A B^{2}+B C^{2}=(7 k)^{2}+(8 k)^{2}$ $=113 \mat...
Read More →The unpaired electrons in Al and Si are present in 3p orbital.
Question: The unpaired electrons in Al and Si are present in 3p orbital. Which electrons will experience more effective nuclear charge from the nucleus? Solution: Nuclear charge is defined as the net positive charge experienced by an electron in a multi-electron atom. The higher the atomic number, the higher is the nuclear charge. Silicon has 14 protons while aluminium has 13 protons. Hence, silicon has a larger nuclear charge of $(+14)$ than aluminium, which has a nuclear charge of $(+13)$. Thu...
Read More →Among the following pairs of orbitals which orbital will experience the larger effective nuclear charge?
Question: Among the following pairs of orbitals which orbital will experience the larger effective nuclear charge? (i) $2 s$ and $3 s$, (ii) $4 d$ and $4 f$, (iii) $3 d$ and $3 p$ Solution: Nuclear charge is defined as the net positive charge experienced by an electron in the orbital of a multi-electron atom. The closer the orbital, the greater is the nuclear charge experienced by the electron (s) in it (i)The electron(s) present in the 2sorbital will experience greater nuclear charge (being clo...
Read More →If $\angle \mathrm{A}$ and $\angle \mathrm{B}$ are acute angles such that $\cos \mathrm{A}=\cos \mathrm{B}$,
[question] Question. If $\angle \mathrm{A}$ and $\angle \mathrm{B}$ are acute angles such that $\cos \mathrm{A}=\cos \mathrm{B}$, then show that $\angle \mathrm{A}=\angle \mathrm{B}$. [/question] [solution] Solution: In figure $\angle \mathrm{A}$ and $\angle \mathrm{B}$ are acute angles of $\triangle \mathrm{ABC}$. Draw $C D \perp A B$ We are given that $\cos A=\cos B$ $\Rightarrow \frac{\mathbf{A D}}{\mathbf{A C}}=\frac{\mathbf{B D}}{\mathbf{B C}}$ $\Rightarrow \frac{\mathbf{A D}}{\mathbf{B D}}...
Read More →Discuss the factors responsible for ascent of xylem sap in plants.
Question: Discuss the factors responsible for ascent of xylem sap in plants. Solution: Transpirational pull is responsible for the ascent of water in the xylem. This ascent of water is dependent on the following physical factors: Cohesion Mutual attraction between water molecules Surface tension Responsible for the greater attraction between water molecules in liquid phase than in gaseous phase Adhesion Attraction of water molecules to polar surfaces Capillarity Ability of water to rise in thin ...
Read More →The bromine atom possesses 35 electrons. It contains 6 electrons in 2p orbital, 6 electrons in 3p orbital and 5 electrons in 4p orbital.
Question: The bromine atom possesses 35 electrons. It contains 6 electrons in $2 p$ orbital, 6 electrons in $3 p$ orbital and 5 electrons in $4 p$ orbital. Which of these electron experiences the lowest effective nuclear charge? Solution: Nuclear charge experienced by an electron (present in a multi-electron atom) is dependant upon the distance between the nucleus and the orbital, in which the electron is present. As the distance increases, the effective nuclear charge also decreases. Amongp-orb...
Read More →Given $\sec \theta=\frac{\mathbf{1 3}}{\mathbf{1 2}}$, calculate all other trigonometric ratios.
[question] Question. Given $\sec \theta=\frac{\mathbf{1 3}}{\mathbf{1 2}}$, calculate all other trigonometric ratios. [/question] [solution] Solution: $\sec \theta=\frac{13}{12}$ $\Rightarrow \frac{A C}{B C}=\frac{13}{12}$ By Pythagoras Theorem, $\mathrm{AC}^{2}=\mathrm{AB}^{2}+\mathrm{BC}^{2}$ $(13 k)^{2}=A B^{2}+(12 k)^{2}$ $\mathrm{AB}^{2}=169 \mathrm{k}^{2}-144 \mathrm{k}^{2}$ $\mathrm{AB}=\sqrt{25 \mathrm{k}^{2}}=5 \mathrm{k}$ $\sin \theta=\frac{\mathbf{A B}}{\mathbf{A C}}=\frac{5 \mathbf{k...
Read More →The quantum numbers of six electrons are given below. Arrange them in order of increasing energies
Question: The quantum numbers of six electrons are given below. Arrange them in orderof increasing energies. If any of these combination(s) has/have the same energy lists: 1. $n=4, I=2, m_{i}=-2, m_{s}=-1 / 2$ 2. $n=3, l=2, m_{i}=1, m_{s}=+1 / 2$ 3. $n=4, l=1, m_{i}=0, m_{s}=+1 / 2$ 4. $n=3,1=2, m_{i}=-2, m_{s}=-1 / 2$ 5. $n=3, I=1, m_{i}=-1, m_{s}=+1 / 2$ 6. $n=4, l=1, m_{i}=0, m_{s}=+1 / 2$ Solution: For $n=4$ and $/=2$, the orbital occupied is $4 d$. For $n=3$ and $/=2$, the orbital occupied ...
Read More →If the position of the electron is measured within an accuracy of + 0.002 nm, calculate the uncertainty in the momentum of the electron.
Question: If the position of the electron is measured within an accuracy of $+0.002 \mathrm{~nm}$, calculate the uncertainty in the momentum of the electron. Suppose the momentum of the electron is $\mathrm{h} / 4 \pi_{\mathrm{m}} \times 0.05$ $\mathrm{nm}$, is there any problem in defining this value. Solution: From Heisenbero's uncertainty principle. $\Delta x \times \Delta p=\frac{\mathrm{h}}{4 \pi} \Rightarrow \Delta p=\frac{1}{\Delta x} \cdot \frac{\mathrm{h}}{4 \pi}$ Where, $\Delta x=$ unc...
Read More →Given 15 cot A = 8, find sin A and sec A.
[question] Question. Given 15 cot A = 8, find sin A and sec A. [/question] [solution] Solution: $\cot A=\frac{8}{15}$ $\Rightarrow \frac{\mathbf{A B}}{\mathbf{B C}}=\frac{\mathbf{8}}{\mathbf{1 5}}$ $\Rightarrow \mathrm{AB}=8 \mathrm{k}$ and $\mathrm{BC}=15 \mathrm{k}$ Now, $A C=\sqrt{(8 k)^{2}+(15 k)^{2}}=17 k$ $\sin A=\frac{B C}{A C}=\frac{15 k}{17 k}=\frac{15}{17}, \quad \sec A=\frac{A C}{A B}=\frac{17 k}{8 k}=\frac{17}{8}$ [/solution]...
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