10th Science Quarterly Exam 2024
Question Paper with Solutions | Dharmapuri District
PART - I (12 x 1 = 12)
Choose the correct answer.
1. One kilogram force equals to ...................
- a) 9.8 dyne
- b) 9.8 x 10⁴ N
- c) 98 x 10⁴ dyne
- d) 980 dyne
Answer: c) 98 x 10⁴ dyne
Explanation: 1 kilogram force (kgf) = 9.8 N. We know that 1 N = 10⁵ dyne. Therefore, 9.8 N = 9.8 x 10⁵ dyne = 98 x 10⁴ dyne.
Explanation: 1 kilogram force (kgf) = 9.8 N. We know that 1 N = 10⁵ dyne. Therefore, 9.8 N = 9.8 x 10⁵ dyne = 98 x 10⁴ dyne.
2. The value of universal gas constant
- a) 3.81 Jmol⁻¹ K⁻¹
- b) 8.03 Jmol⁻¹ K⁻¹
- c) 1.38 Jmol⁻¹ K⁻¹
- d) 8.31 Jmol⁻¹ K⁻¹
Answer: d) 8.31 Jmol⁻¹ K⁻¹
Explanation: The standard value of the universal gas constant (R) is 8.31 Jmol⁻¹K⁻¹.
Explanation: The standard value of the universal gas constant (R) is 8.31 Jmol⁻¹K⁻¹.
3. Kilowatt hour is the unit of ................
- a) resistivity
- b) Conductivity
- c) Electrical energy
- d) Electrical power
Answer: c) Electrical energy
Explanation: Kilowatt-hour (kWh) is a commercial unit of electrical energy consumed. 1 kWh = 3.6 x 10⁶ Joules.
Explanation: Kilowatt-hour (kWh) is a commercial unit of electrical energy consumed. 1 kWh = 3.6 x 10⁶ Joules.
4. 1 mole of any substance contains ................. Molecules.
- a) 6.023x10²³
- b) 6.023 x 10⁻²³
- c) 3.0115x 10²³
- d) 12.046x10²³
Answer: a) 6.023x10²³
Explanation: One mole of any substance contains Avogadro's number of particles (atoms, molecules, or ions), which is approximately 6.023 x 10²³.
Explanation: One mole of any substance contains Avogadro's number of particles (atoms, molecules, or ions), which is approximately 6.023 x 10²³.
5. Which of the following inert gases have 2 electrons in the outermost shell.
- a) He
- b) Ne
- c) Ar
- d) Kr
Answer: a) He
Explanation: Helium (He) has an atomic number of 2, and its electronic configuration is 1s². It has only one shell (K-shell) which is also its outermost shell, containing 2 electrons (duplet configuration). All other inert gases have 8 electrons in their outermost shell (octet configuration).
Explanation: Helium (He) has an atomic number of 2, and its electronic configuration is 1s². It has only one shell (K-shell) which is also its outermost shell, containing 2 electrons (duplet configuration). All other inert gases have 8 electrons in their outermost shell (octet configuration).
6. When pressure is increased at constant temperature the solubility of gases in liquid...........
- a) No change
- b) increases
- c) decreases
- d) no reaction
Answer: b) increases
Explanation: According to Henry's Law, the solubility of a gas in a liquid is directly proportional to the pressure of the gas over the solution at a constant temperature.
Explanation: According to Henry's Law, the solubility of a gas in a liquid is directly proportional to the pressure of the gas over the solution at a constant temperature.
7. Which is formed during anaerobic respiration
- a) Carbohydrate
- b) Ethyl alcohol
- c) Acetyl CoA
- d) Pyruvate
Answer: b) Ethyl alcohol
Explanation: In anaerobic respiration (like alcoholic fermentation in yeast), glucose is first broken down into pyruvate (glycolysis). Then, pyruvate is converted into ethyl alcohol and carbon dioxide. While pyruvate is an intermediate, ethyl alcohol is a final product.
Explanation: In anaerobic respiration (like alcoholic fermentation in yeast), glucose is first broken down into pyruvate (glycolysis). Then, pyruvate is converted into ethyl alcohol and carbon dioxide. While pyruvate is an intermediate, ethyl alcohol is a final product.
8. The wall of human heart is made of ................
- a) Endocardium
- b) Epicardium
- c) Myocardium
- d) All of the above
Answer: d) All of the above
Explanation: The wall of the human heart is composed of three layers: the outer Epicardium, the middle Myocardium (cardiac muscle), and the inner Endocardium.
Explanation: The wall of the human heart is composed of three layers: the outer Epicardium, the middle Myocardium (cardiac muscle), and the inner Endocardium.
9. Nerve cells do not possess
- a) neurilemma
- b) Sarcolemma
- c) axon
- d) dendrites
Answer: b) Sarcolemma
Explanation: Sarcolemma is the cell membrane of a muscle fiber (muscle cell). Neurilemma, axon, and dendrites are all parts or associated structures of a nerve cell (neuron).
Explanation: Sarcolemma is the cell membrane of a muscle fiber (muscle cell). Neurilemma, axon, and dendrites are all parts or associated structures of a nerve cell (neuron).
10. Which organ act as both exocrine gland as well as endocrine gland
- a) Pancreas
- b) Kidney
- c) Liver
- d) Lungs
Answer: a) Pancreas
Explanation: The pancreas is a heterocrine gland. Its exocrine part secretes digestive enzymes (pancreatic juice), and its endocrine part (Islets of Langerhans) secretes hormones like insulin and glucagon.
Explanation: The pancreas is a heterocrine gland. Its exocrine part secretes digestive enzymes (pancreatic juice), and its endocrine part (Islets of Langerhans) secretes hormones like insulin and glucagon.
11. Which one of the following is an IUCD.
- a) Copper-T
- b) Oral pills
- c) Diaphragm
- d) Tubectomy
Answer: a) Copper-T
Explanation: IUCD stands for Intra-Uterine Contraceptive Device. Copper-T is a type of IUCD that is placed in the uterus to prevent pregnancy.
Explanation: IUCD stands for Intra-Uterine Contraceptive Device. Copper-T is a type of IUCD that is placed in the uterus to prevent pregnancy.
12. The region of the chromosome where the spindle fibers get attached during cell division.
- a) Chromomere
- b) Centrosome
- c) Centromere
- d) Chromonema
Answer: c) Centromere
Explanation: The centromere is a constricted region on a chromosome that holds the two sister chromatids together and serves as the attachment point for spindle fibers during cell division.
Explanation: The centromere is a constricted region on a chromosome that holds the two sister chromatids together and serves as the attachment point for spindle fibers during cell division.
PART - II (7 x 2 = 14)
Answer any 7 questions. Question no: 22 is Compulsory.
13. State Rayleigh's law of scattering.
Rayleigh's law of scattering states that the amount of scattering of light is inversely proportional to the fourth power of its wavelength.
Mathematically: Amount of Scattering (S) ∝ 1/λ⁴, where λ is the wavelength of light.
Mathematically: Amount of Scattering (S) ∝ 1/λ⁴, where λ is the wavelength of light.
14. Distinguish between linear, aerial or superficial expansion.
| Basis | Linear Expansion | Superficial/Aerial Expansion |
|---|---|---|
| Definition | The expansion in length of a solid when it is heated. | The expansion in the area of a solid when it is heated. |
| Dimension | It occurs in one dimension (length). | It occurs in two dimensions (length and breadth). |
| Coefficient | Coefficient of linear expansion (α). | Coefficient of superficial expansion (β). |
| Formula | ΔL/L₀ = α ΔT | ΔA/A₀ = β ΔT |
15. Why is tungsten metal used in bulbs, but not in fuse wires?
- Tungsten in Bulbs: Tungsten has a very high melting point (3422 °C). This allows it to be heated to a very high temperature to emit light (incandescence) without melting.
- Fuse Wires: Fuse wires are safety devices designed to protect circuits from excessive current. They must have a low melting point so that they can melt and break the circuit when the current exceeds a safe limit. Tungsten's high melting point makes it unsuitable for this purpose.
16. What is rust? Give the equation for formation of rust.
Rust: Rust is a red or brown coating of hydrated ferric oxide that forms on the surface of iron or steel when it is exposed to oxygen and moisture.
Chemical Formula: Fe₂O₃.xH₂O
Equation for formation of rust:
4Fe + 3O₂ + xH₂O → 2Fe₂O₃.xH₂O (Hydrated ferric oxide)
Chemical Formula: Fe₂O₃.xH₂O
Equation for formation of rust:
4Fe + 3O₂ + xH₂O → 2Fe₂O₃.xH₂O (Hydrated ferric oxide)
17. Why is the teeth of rabbit called heterodont?
The teeth of a rabbit are called heterodont because they are of different types, each adapted for a specific function. A rabbit's dentition consists of:
- Incisors: For gnawing.
- Premolars and Molars: For chewing and grinding.
18. Match it:
- a) Symplastic pathway - Plasmodesmata
- b) Transpiration - Leaf
- c) Osmosis - Pressure gradient
- d) Root pressure - Pressure in Xylem
19. Why are thyroid hormones referred to as personality hormone?
Thyroid hormones (thyroxine) are called 'personality hormones' because they regulate the Basal Metabolic Rate (BMR) of the body. They are essential for normal physical, mental, and personality development. A deficiency (hypothyroidism) or excess (hyperthyroidism) of these hormones can lead to significant changes in a person's mood, energy levels, and overall physical and mental well-being, thus affecting their personality.
20. Identify the parts A, B, C and D
The given diagram is of a Pollen Grain. The parts are:
- A: Exine
- B: Intine
- C: Generative Cell
- D: Vegetative Nucleus
21. What do you understand by the term phenotype and genotype?
- Genotype: It is the genetic constitution or makeup of an organism. It represents the combination of alleles for a particular trait (e.g., TT, Tt, or tt for height in pea plants).
- Phenotype: It is the observable physical or external characteristic of an organism, which is determined by its genotype and influenced by the environment (e.g., tall or dwarf for height).
22. (Compulsory) 3.5 litres of ethanol is present in 15 liters of aqueous solution of ethanol. Calculate volume percent of ethanol solution.
Given:
Volume percent = (Volume of solute / Volume of solution) x 100
Calculation:
Volume percent = (3.5 / 15) x 100
Volume percent = 0.2333 x 100
Volume percent = 23.33 %
Therefore, the volume percent of the ethanol solution is 23.33%.
- Volume of solute (ethanol) = 3.5 litres
- Volume of solution = 15 litres
Volume percent = (Volume of solute / Volume of solution) x 100
Calculation:
Volume percent = (3.5 / 15) x 100
Volume percent = 0.2333 x 100
Volume percent = 23.33 %
Therefore, the volume percent of the ethanol solution is 23.33%.
PART - III (7 x 4 = 28)
Answer any 7 questions. Question no: 32 is Compulsory.
23. What is universal law? Write any 2 applications.
Universal Law of Gravitation:
Newton's Universal Law of Gravitation states that every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.
Formula: F = G (m₁m₂ / r²)
Applications:
Newton's Universal Law of Gravitation states that every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.
Formula: F = G (m₁m₂ / r²)
Applications:
- It helps in determining the masses of the Earth, the Sun, the moon, and other celestial bodies.
- It helps to explain the motion of the moon around the Earth and the motion of planets around the Sun.
- It is used in predicting the paths of astronomical bodies and in launching artificial satellites and space probes.
24. Differentiate the eye defects: Myopia and Hypermetropia.
| Feature | Myopia (Near-sightedness) | Hypermetropia (Far-sightedness) |
|---|---|---|
| Definition | The inability to see distant objects clearly, while near objects are clear. | The inability to see near objects clearly, while distant objects are clear. |
| Cause | Elongation of the eyeball or high converging power of the eye lens. | Shortening of the eyeball or low converging power of the eye lens. |
| Image Formation | The image of a distant object is formed in front of the retina. | The image of a near object is formed behind the retina. |
| Correction | Corrected by using a concave lens of appropriate focal length. | Corrected by using a convex lens of appropriate focal length. |
25. Calculate the % of each element in calcium carbonate (CaCO₃). (Atomic mass: C-12, O-16, Ca-40)
Step 1: Calculate the molecular mass of CaCO₃.
Molecular mass of CaCO₃ = (Atomic mass of Ca) + (Atomic mass of C) + 3 x (Atomic mass of O)
= 40 + 12 + 3(16)
= 40 + 12 + 48
= 100 g/mol
Step 2: Calculate the percentage of each element.
% of Calcium (Ca) = (Mass of Ca / Molecular mass of CaCO₃) x 100
= (40 / 100) x 100 = 40%
% of Carbon (C) = (Mass of C / Molecular mass of CaCO₃) x 100
= (12 / 100) x 100 = 12%
% of Oxygen (O) = (Mass of 3 O atoms / Molecular mass of CaCO₃) x 100
= (48 / 100) x 100 = 48%
Molecular mass of CaCO₃ = (Atomic mass of Ca) + (Atomic mass of C) + 3 x (Atomic mass of O)
= 40 + 12 + 3(16)
= 40 + 12 + 48
= 100 g/mol
Step 2: Calculate the percentage of each element.
% of Calcium (Ca) = (Mass of Ca / Molecular mass of CaCO₃) x 100
= (40 / 100) x 100 = 40%
% of Carbon (C) = (Mass of C / Molecular mass of CaCO₃) x 100
= (12 / 100) x 100 = 12%
% of Oxygen (O) = (Mass of 3 O atoms / Molecular mass of CaCO₃) x 100
= (48 / 100) x 100 = 48%
26. a) Identify the bond between H and F in HF molecule. b) What property forms the basis of identification? c) How does the property vary in periods and in groups?
a) Bond in HF molecule: The bond between Hydrogen (H) and Fluorine (F) in the HF molecule is a polar covalent bond.
b) Basis of identification: The basis for identifying the bond type is the difference in electronegativity between the two atoms. Fluorine is the most electronegative element, and its high electronegativity compared to hydrogen results in an unequal sharing of electrons, creating a polar bond.
c) Variation of Electronegativity:
b) Basis of identification: The basis for identifying the bond type is the difference in electronegativity between the two atoms. Fluorine is the most electronegative element, and its high electronegativity compared to hydrogen results in an unequal sharing of electrons, creating a polar bond.
c) Variation of Electronegativity:
- In a Period: Electronegativity generally increases from left to right across a period in the periodic table.
- In a Group: Electronegativity generally decreases from top to bottom down a group.
27. a) What is collateral vascular bundle? b) Where does the carbon that is used in photosynthesis come from? c) What is the common step in aerobic and anaerobic pathway?
a) Collateral vascular bundle: A vascular bundle in which the xylem and phloem are present on the same radius, with the phloem located towards the outside (periphery) and the xylem located towards the inside (centre). This is the most common type of vascular bundle found in dicot stems.
b) Source of carbon for photosynthesis: The carbon used in photosynthesis comes from carbon dioxide (CO₂) in the atmosphere. Plants take in CO₂ through small pores on their leaves called stomata.
c) Common step in aerobic and anaerobic pathway: The common step for both aerobic and anaerobic respiration is Glycolysis. It is the process where a molecule of glucose is broken down into two molecules of pyruvic acid in the cytoplasm of the cell.
b) Source of carbon for photosynthesis: The carbon used in photosynthesis comes from carbon dioxide (CO₂) in the atmosphere. Plants take in CO₂ through small pores on their leaves called stomata.
c) Common step in aerobic and anaerobic pathway: The common step for both aerobic and anaerobic respiration is Glycolysis. It is the process where a molecule of glucose is broken down into two molecules of pyruvic acid in the cytoplasm of the cell.
28. How does locomotion take place in leech?
Leeches exhibit two main types of locomotion:
- Looping or Crawling Movement: This is the primary mode of movement on a solid surface.
- The leech attaches its posterior sucker firmly to the substratum.
- It then contracts its longitudinal muscles, causing the body to shorten and arch upwards like a loop.
- Next, it attaches its anterior sucker to the surface.
- Finally, it releases the posterior sucker and contracts its circular muscles, causing the body to extend forward. This cycle is repeated.
- Swimming Movement: In water, the leech flattens its body and performs successive undulating movements to swim actively.
29. State whether True or False. If false write the correct statement.
a) The phloem is responsible for the translocation of food
b) When guard cells lose water the stoma opens
c) What is cohesion?
a) The phloem is responsible for the translocation of food:
True.
b) When guard cells lose water the stoma opens:
False.
Correct statement: When guard cells lose water, they become flaccid, and the stoma closes.
c) What is cohesion?
Cohesion is the force of attraction between molecules of the same substance. For example, the attraction between one water molecule and another water molecule is cohesion.
True.
b) When guard cells lose water the stoma opens:
False.
Correct statement: When guard cells lose water, they become flaccid, and the stoma closes.
c) What is cohesion?
Cohesion is the force of attraction between molecules of the same substance. For example, the attraction between one water molecule and another water molecule is cohesion.
30. a) What are the structures involved in the protection of brain? b) Define reflex arc.
a) Structures protecting the brain:
The brain is protected by three main structures:
- Cranium (Skull): A hard, bony box that encloses the brain and protects it from physical injury.
- Meninges: Three protective membranes covering the brain and spinal cord. They are the outer Dura mater, the middle Arachnoid mater, and the inner Pia mater.
- Cerebrospinal Fluid (CSF): A fluid found between the meninges that acts as a shock absorber, protecting the brain from jerks and shocks.
31. What is colostrum? How is milk production hormonally regulated?
Colostrum: Colostrum is the first form of milk produced by the mammary glands of mammals immediately following delivery of the newborn. It is a yellowish, sticky fluid rich in proteins, vitamins, minerals, and antibodies (especially IgA), which provides passive immunity to the baby and protects it from infections.
Hormonal Regulation of Milk Production:
Hormonal Regulation of Milk Production:
- Prolactin: This hormone, secreted by the anterior pituitary gland, is responsible for stimulating the production (synthesis) of milk in the mammary glands (alveoli).
- Oxytocin: This hormone, released from the posterior pituitary gland, is responsible for the ejection or "let-down" of milk from the mammary glands in response to the baby suckling.
32. (Compulsory) The resistance of a wire of length 10 m is 2 ohm. If the area of cross section of the wire is 2x10⁻⁷ m², determine its (i) resistivity (ii) Conductance.
Given:
The formula for resistance is R = ρL/A.
Rearranging for resistivity, ρ = RA/L.
ρ = (2 Ω × 2 × 10⁻⁷ m²) / 10 m
ρ = (4 × 10⁻⁷) / 10
ρ = 4 × 10⁻⁸ Ωm
(ii) Conductance (G):
Conductance is the reciprocal of resistance.
G = 1/R
G = 1 / 2 Ω
G = 0.5 mho (or Siemens, S)
- Length (L) = 10 m
- Resistance (R) = 2 Ω
- Area of cross-section (A) = 2 x 10⁻⁷ m²
The formula for resistance is R = ρL/A.
Rearranging for resistivity, ρ = RA/L.
ρ = (2 Ω × 2 × 10⁻⁷ m²) / 10 m
ρ = (4 × 10⁻⁷) / 10
ρ = 4 × 10⁻⁸ Ωm
(ii) Conductance (G):
Conductance is the reciprocal of resistance.
G = 1/R
G = 1 / 2 Ω
G = 0.5 mho (or Siemens, S)
PART - IV (3 x 7 = 21)
Answer the following questions in detail.
33. a) Deduce the equation of a force using Newton's second law of motion (OR) b) Derive the ideal gas equation.
a) Deduce the equation of a force using Newton's second law of motion
Newton's second law of motion states that the force acting on a body is directly proportional to the rate of change of its linear momentum and the change in momentum takes place in the direction of the force.
Let 'm' be the mass of a moving body, moving with an initial velocity 'u'.
Initial momentum of the body, Pᵢ = mu.
Now, let a force 'F' act on the body for a time 't', causing its final velocity to become 'v'.
Final momentum of the body, Pբ = mv.
Change in momentum = Final momentum - Initial momentum
ΔP = Pբ - Pᵢ = mv - mu = m(v - u).
Rate of change of momentum = Change in momentum / time
= m(v - u) / t.
According to Newton's second law:
F ∝ Rate of change of momentum
F ∝ m(v - u) / t
We know that acceleration (a) = (v - u) / t (rate of change of velocity).
Therefore, F ∝ ma.
To replace the proportionality sign with an equality sign, we introduce a constant 'k'.
F = kma.
The value of the constant k is chosen to be 1 by defining the unit of force. One unit of force is defined as the force required to produce an acceleration of 1 m/s² in a body of mass 1 kg. Thus, k = 1.
Hence, the equation for force is derived as: F = ma
(OR)
b) Derive the ideal gas equation
The ideal gas equation is derived by combining three fundamental gas laws: Boyle's Law, Charles's Law, and Avogadro's Law.
1. Boyle's Law: At constant temperature (T) and number of moles (n), the volume (V) of a gas is inversely proportional to its pressure (P).
V ∝ 1/P ..........(1)
2. Charles's Law: At constant pressure (P) and number of moles (n), the volume (V) of a gas is directly proportional to its absolute temperature (T).
V ∝ T ..........(2)
3. Avogadro's Law: At constant pressure (P) and temperature (T), the volume (V) of a gas is directly proportional to the number of moles (n).
V ∝ n ..........(3)
By combining equations (1), (2), and (3), we get:
V ∝ nT/P
To change the proportionality into an equality, we introduce a constant, R, which is called the Universal Gas Constant.
V = R (nT/P)
Rearranging the terms, we get the ideal gas equation:
PV = nRT
This equation relates the pressure, volume, temperature, and number of moles of an ideal gas.
Newton's second law of motion states that the force acting on a body is directly proportional to the rate of change of its linear momentum and the change in momentum takes place in the direction of the force.
Let 'm' be the mass of a moving body, moving with an initial velocity 'u'.
Initial momentum of the body, Pᵢ = mu.
Now, let a force 'F' act on the body for a time 't', causing its final velocity to become 'v'.
Final momentum of the body, Pբ = mv.
Change in momentum = Final momentum - Initial momentum
ΔP = Pբ - Pᵢ = mv - mu = m(v - u).
Rate of change of momentum = Change in momentum / time
= m(v - u) / t.
According to Newton's second law:
F ∝ Rate of change of momentum
F ∝ m(v - u) / t
We know that acceleration (a) = (v - u) / t (rate of change of velocity).
Therefore, F ∝ ma.
To replace the proportionality sign with an equality sign, we introduce a constant 'k'.
F = kma.
The value of the constant k is chosen to be 1 by defining the unit of force. One unit of force is defined as the force required to produce an acceleration of 1 m/s² in a body of mass 1 kg. Thus, k = 1.
Hence, the equation for force is derived as: F = ma
(OR)
b) Derive the ideal gas equation
The ideal gas equation is derived by combining three fundamental gas laws: Boyle's Law, Charles's Law, and Avogadro's Law.
1. Boyle's Law: At constant temperature (T) and number of moles (n), the volume (V) of a gas is inversely proportional to its pressure (P).
V ∝ 1/P ..........(1)
2. Charles's Law: At constant pressure (P) and number of moles (n), the volume (V) of a gas is directly proportional to its absolute temperature (T).
V ∝ T ..........(2)
3. Avogadro's Law: At constant pressure (P) and temperature (T), the volume (V) of a gas is directly proportional to the number of moles (n).
V ∝ n ..........(3)
By combining equations (1), (2), and (3), we get:
V ∝ nT/P
To change the proportionality into an equality, we introduce a constant, R, which is called the Universal Gas Constant.
V = R (nT/P)
Rearranging the terms, we get the ideal gas equation:
PV = nRT
This equation relates the pressure, volume, temperature, and number of moles of an ideal gas.
34. a) Calcium carbonate is decomposed on heating in the following reaction.
CaCO₃ → CaO + CO₂
i) How many moles of calcium carbonate are involved in this reaction?
ii) Calculate the gram molecular mass of calcium carbonate involved in this reaction.
iii) How many moles of CO₂ are there in this equation?
(OR)
b) Write notes on various factors affecting solubility.
a) Analysis of the decomposition of Calcium Carbonate
The balanced chemical equation is: CaCO₃(s) → CaO(s) + CO₂(g)
i) How many moles of calcium carbonate are involved in this reaction?
Based on the stoichiometry of the balanced equation, the coefficient of CaCO₃ is 1. Therefore, 1 mole of calcium carbonate is involved in this reaction.
ii) Calculate the gram molecular mass of calcium carbonate involved in this reaction.
Gram molecular mass of CaCO₃ = (Atomic mass of Ca) + (Atomic mass of C) + 3 × (Atomic mass of O)
= 40 + 12 + 3(16)
= 40 + 12 + 48
= 100 g/mol
iii) How many moles of CO₂ are there in this equation?
From the balanced equation, the stoichiometric coefficient for CO₂ is 1. Therefore, 1 mole of carbon dioxide is produced.
(OR)
b) Factors affecting solubility
The solubility of a substance depends on several factors:
The balanced chemical equation is: CaCO₃(s) → CaO(s) + CO₂(g)
i) How many moles of calcium carbonate are involved in this reaction?
Based on the stoichiometry of the balanced equation, the coefficient of CaCO₃ is 1. Therefore, 1 mole of calcium carbonate is involved in this reaction.
ii) Calculate the gram molecular mass of calcium carbonate involved in this reaction.
Gram molecular mass of CaCO₃ = (Atomic mass of Ca) + (Atomic mass of C) + 3 × (Atomic mass of O)
= 40 + 12 + 3(16)
= 40 + 12 + 48
= 100 g/mol
iii) How many moles of CO₂ are there in this equation?
From the balanced equation, the stoichiometric coefficient for CO₂ is 1. Therefore, 1 mole of carbon dioxide is produced.
(OR)
b) Factors affecting solubility
The solubility of a substance depends on several factors:
- Nature of the Solute and Solvent: The fundamental principle is "like dissolves like".
- Polar solutes (like common salt, NaCl) tend to dissolve in polar solvents (like water, H₂O).
- Non-polar solutes (like grease or oil) tend to dissolve in non-polar solvents (like carbon tetrachloride, CCl₄).
- Temperature:
- Solids in Liquids: For most solid solutes, solubility increases as the temperature of the solvent increases. For example, more sugar dissolves in hot water than in cold water. However, for some substances like cerium sulfate (Ce₂(SO₄)₃), solubility decreases with an increase in temperature.
- Gases in Liquids: The solubility of gases in liquids decreases as the temperature increases. This is why boiled water has a "flat" taste, as dissolved gases like oxygen and carbon dioxide escape upon heating.
- Pressure:
- Solids and Liquids: Pressure has a negligible effect on the solubility of solid and liquid solutes.
- Gases in Liquids: The effect of pressure is significant. According to Henry's Law, the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid. This is why carbonated drinks are bottled under high pressure to dissolve more CO₂. When the bottle is opened, the pressure drops, and the excess gas escapes as bubbles.
35. a) i) Name the gaseous plant hormone. Describe its three different actions in plants.
ii) Which hormone is known as stress hormone in plants? Why ?
iii) What is Bolting?
(OR)
b) What is the structure of DNA organized? What is the biological significance of DNA?
a) Plant Hormones
i) Gaseous Plant Hormone and its Actions:
The gaseous plant hormone is Ethylene (C₂H₄).
Three actions of Ethylene:
Abscisic Acid (ABA) is known as the stress hormone.
Reason: It is produced in plants during periods of environmental stress, such as drought, high salinity, or extreme temperatures. It helps the plant cope with these adverse conditions, primarily by inducing the closure of stomata to reduce water loss through transpiration. This protective role during stress is why it is called the stress hormone.
iii) What is Bolting?
Bolting is the premature production of a long flowering stem in plants (especially rosette plants like cabbage and beets) before they reach full vegetative growth. This process is induced by the plant hormone Gibberellin.
(OR)
b) DNA Structure and Significance
Structure of DNA:
DNA (Deoxyribonucleic Acid) is organized as a double helix, as proposed by Watson and Crick. This structure resembles a twisted ladder.
Biological Significance of DNA:
i) Gaseous Plant Hormone and its Actions:
The gaseous plant hormone is Ethylene (C₂H₄).
Three actions of Ethylene:
- Fruit Ripening: Ethylene is widely used in agriculture to promote the ripening of fruits like bananas, mangoes, and tomatoes. It enhances the process of ripening, leading to changes in colour, texture, and aroma.
- Senescence and Abscission: It accelerates the aging (senescence) of plant parts and promotes the shedding (abscission) of leaves, flowers, and fruits.
- Inhibition of Stem Elongation: Ethylene generally inhibits stem elongation and promotes transverse or horizontal growth, causing the stem to become short and thick.
Abscisic Acid (ABA) is known as the stress hormone.
Reason: It is produced in plants during periods of environmental stress, such as drought, high salinity, or extreme temperatures. It helps the plant cope with these adverse conditions, primarily by inducing the closure of stomata to reduce water loss through transpiration. This protective role during stress is why it is called the stress hormone.
iii) What is Bolting?
Bolting is the premature production of a long flowering stem in plants (especially rosette plants like cabbage and beets) before they reach full vegetative growth. This process is induced by the plant hormone Gibberellin.
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b) DNA Structure and Significance
Structure of DNA:
DNA (Deoxyribonucleic Acid) is organized as a double helix, as proposed by Watson and Crick. This structure resembles a twisted ladder.
- Components: Each strand of the DNA is a polynucleotide chain, made up of repeating units called nucleotides. Each nucleotide consists of three components:
- A deoxyribose sugar
- A phosphate group
- A nitrogenous base
- Nitrogenous Bases: There are four types of nitrogenous bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). A and G are purines, while C and T are pyrimidines.
- Double Helix: Two polynucleotide strands are coiled around each other to form a double helix. The sugar and phosphate groups form the backbone of the ladder, while the nitrogenous bases form the rungs.
- Base Pairing: The bases on the two strands are linked by hydrogen bonds according to a specific rule: Adenine always pairs with Thymine (A-T) with two hydrogen bonds, and Guanine always pairs with Cytosine (G-C) with three hydrogen bonds. This is known as complementary base pairing.
Biological Significance of DNA:
- Carrier of Genetic Information: DNA is the primary genetic material in most organisms. It carries the instructions (genes) for the development, functioning, growth, and reproduction of all living things.
- Heredity: DNA is responsible for the transmission of genetic information from one generation to the next.
- Control of Metabolism: It controls all the metabolic activities of the cell by directing the synthesis of specific proteins and enzymes.
- Variation: Variations, which are essential for evolution, arise due to changes (mutations) in the DNA sequence.