Let's analyze the options:

Option (a): 2FeSO₄ → Fe₂O₃ + SO₂ + SO₃ This is a decomposition reaction, but it's typically thermally driven (requires heat), not light.

Option (b): 2H₂O → 2H₂ + O₂ This is a decomposition reaction, but it requires a significant amount of energy, usually electrical energy (electrolysis) or heat.

Option (c): 2AgBr → 2Ag + Br₂ This is a decomposition reaction where silver bromide (AgBr) decomposes into silver (Ag) and bromine (Br₂) when exposed to light. This is a classic example of a photochemical decomposition reaction used in photography.

Option (d): CaCO₃ → CaO + CO₂ This is a decomposition reaction, but it is typically driven by heat.

Therefore, the decomposition reaction driven by light is option (c).

For example, zinc oxide reacts with hydrochloric acid (an acid): ZnO + 2HCl → ZnCl₂ + H₂O

And it also reacts with sodium hydroxide (a base): ZnO + 2NaOH + H₂O → Na₂[Zn(OH)₄] (sodium zincate)

Aluminum oxide behaves similarly.

Let’s examine the common hydrated forms of these compounds: FeSO₄: Commonly exists as FeSO₄·7H₂O (heptahydrate) CuSO₄: Commonly exists as CuSO₄·5H₂O (pentahydrate) CaSO₄: Commonly exists as CaSO₄·2H₂O (dihydrate) or anhydrous CaSO₄ Na₂CO₃: Commonly exists as Na₂CO₃·10H₂O (decahydrate)

Comparing the number of water molecules in the common hydrated forms (7, 5, 2, and 10), we find that Sodium Carbonate (Na₂CO₃) has the maximum number of water molecules.

Let’s list the first few members: 1. Ethyne: C₂H₂ 2. Propyne: C₃H₄ 3. Butyne: C₄H₆

Therefore, the third member is butyne with the formula C₄H₆.

Mercury is the only metal that is liquid at standard room temperature. Bromine is one of the few non-metals that are liquid at standard room temperature.

In redox reactions, oxidation and reduction occur simultaneously. "OIL RIG" helps remember: Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons).

Option (a): NaOH + Zn → NaZnO₂ + H₂O This equation is not balanced. Option (b): 2NaOH + Zn → Na₂ZnO₂ + H₂ This equation is balanced. Option (c): 2NaOH + Zn → NaZnO₂ + H₂ This equation is not balanced. Option (d): 2NaOH + Zn → Na₂ZnO₂ + H₂O This equation is not balanced.

Option (d) is NOT true. Features of an organism (phenotype) are largely determined by the proteins they produce. If the proteins change (due to changes in DNA), the features of the organism are also likely to change.

The neuromuscular junction is where the nervous system communicates with the muscular system to cause muscle contractions.

Therefore, statements (i) and (iv) are correct.

Stomata are tiny pores on the surface of leaves, primarily responsible for gas exchange (taking in carbon dioxide for photosynthesis and releasing oxygen). They are surrounded by guard cells that regulate their opening and closing.

Stomata open when the guard cells become turgid (swollen) due to an influx of water. Conversely, stomata close when the guard cells lose water and become flaccid. This happens when potassium ions leave the guard cells, causing water to flow out by osmosis.

(ii) It does not need carbon dioxide for photosynthesis: When photosynthesis is not active (e.g., at night or during water stress), the stomata tend to close to conserve water.
(iii) Water flows out of the guard cells: This loss of water makes the guard cells flaccid, causing the stomatal pore to close.

Multiple fission is a type of asexual reproduction where the parent organism divides into multiple daughter cells simultaneously. Plasmodium, the parasite that causes malaria, utilizes multiple fission during its life cycle, specifically in the liver stage (schizogony), where it rapidly multiplies. Yeast reproduces through budding, while Leishmania and Paramecium typically undergo binary fission (splitting into two).

A convex lens forms a real, inverted image of the same size as the object when the object is placed at twice the focal length (2f). You can derive this using the lens formula:

Lens Formula: \( \frac{1}{f} = \frac{1}{v} - \frac{1}{u} \)

Magnification Formula: \( m = \frac{v}{u} \)

When the image size is equal to the object size, the magnitude of magnification is 1. For a real, inverted image, \( m = -1 \). Substituting \( v = -u \) into the lens formula gives:

\( \frac{1}{f} = \frac{1}{-u} - \frac{1}{u} \)

\( u = -2f \)

This shows that the object should be placed at twice the focal length of the lens.

The retina contains photoreceptor cells (rods and cones) that convert light into electrical signals, which are then transmitted to the brain via the optic nerve. The cornea and lens refract (bend) light to focus it on the retina. The ciliary muscles control the shape of the lens to adjust focus.

A solenoid is a coil of wire wrapped around a cylindrical core. When a current flows through the solenoid, it creates a magnetic field. Inside the solenoid, the magnetic field lines are nearly parallel and uniform. Option (a) correctly depicts this pattern. The parallel lines inside represent the uniform magnetic field.

Option (b) shows concentric circles, which is the magnetic field pattern around a straight current-carrying wire. Option (c) shows curved field lines inside, which is not representative of the uniform field inside a solenoid. Option (d) depicts a field pattern more characteristic of two opposite magnetic poles facing each other.

Trophic levels represent the different levels in a food chain or food web:

• First Trophic Level: Producers (plants) – These organisms produce their own food through photosynthesis.
• Second Trophic Level: Primary Consumers (herbivores) – These organisms consume producers.
• Third Trophic Level: Secondary Consumers (carnivores) – These organisms consume primary consumers.
• Fourth Trophic Level (and higher): Tertiary Consumers (top carnivores) – These organisms consume secondary consumers.

In the given food chain "Tiger, grass, snake, frog," the primary consumers (herbivores) are missing, making it incomplete.

Reason is false because the amount of oxygen dissolved in water is significantly lower than in air. While air contains about 21% oxygen, dissolved oxygen in water is much less and varies depending on temperature and pollution levels.

Reason is false because rainbows are not formed when the sun is directly overhead. They occur when the sun is behind the observer, and sunlight is refracted, reflected, and dispersed by water droplets at an angle of approximately 42 degrees.

Reason is also true as harmful chemicals enter the food chain through agricultural activities. However, the primary reason for biomagnification is the non-biodegradable nature of these chemicals and their accumulation as they move up the food chain.

Reason is true as nitric acid is a strong oxidizing agent. When zinc reacts with nitric acid, the nascent hydrogen is immediately oxidized to water, while nitric acid gets reduced to nitrogen oxides (e.g., NO₂, NO, or N₂O).

The overall reaction for moderately concentrated nitric acid is:
Zn + 4HNO₃ → Zn(NO₃)₂ + 2NO₂ + 2H₂O

Magnetic field lines represent the direction of the magnetic force that a small north magnetic pole would experience if placed at that point. If two magnetic field lines were to intersect, it would mean that at the point of intersection, the magnetic force would have two different directions, which is not possible.

This indicates that the magnetic field strength and direction are the same at all points in that region.

Justification:
1. Parallel Combination:
The equivalent resistance (R_p) of two 6 Ω resistors in parallel is:
1/R_p = 1/6 + 1/6 = 2/6 = 1/3
R_p = 3 Ω

2. Series Combination:
The total resistance (R_T) is the sum of R_p and the third resistor in series:
R_T = R_p + 6
R_T = 3 + 6 = 9 Ω
Thus, connecting two resistors in parallel and then in series with the third gives the desired total resistance of 9 Ω.

Steps:
1. Total Resistance:

The two resistors are connected in series, so the total resistance (R_T) is:
R_T = 1 Ω + 2 Ω
R_T = 3 Ω

2. Current Calculation:

Using Ohm’s Law (V = IR):
I = V / R_T
I = 6 V / 3 Ω
I = 2 A

3. Power Consumed:

The power consumed by the 2 Ω resistor is:
P = I²R
P = (2 A)² × 2 Ω
P = 4 × 2
P = 8 W

The incident ray is refracted towards the normal upon entering the denser medium (glass) and then refracted away from the normal upon exiting into the rarer medium (air). The emergent ray is parallel to the incident ray but laterally displaced.

Tendrils are specialized thread-like structures that help climbing plants, like pea plants, to attach to and climb up supports. Auxin promotes the growth of tendrils on the side away from the support. This difference in auxin concentration causes the tendril to grow faster on the opposite side, curling around the support and providing anchorage.

This can lead to dehydration, electrolyte imbalances, and other serious health problems as the body fails to maintain proper homeostasis.

Unbalanced Equation:
BaCl_2(aq) + Al₂(SO₄)_3(aq) → BaSO_4(s) + AlCl_3(aq)
The downward arrow indicates that barium sulfate is a precipitate (insoluble solid).

Unbalanced Equation:
Al_(s) + H₂O_(g) → Al₂O_3(s) + H_2(g)
Steam is represented as H₂O_(g) (gaseous water).

A pH below 7 indicates an acidic solution. The lower the pH, the higher the concentration of hydrogen ions (H⁺), which is responsible for the sour taste of tomato juice.

Strong Acids: Completely ionize in water, e.g., HCl_(aq) → H⁺_(aq) + Cl^-_(aq).
Weak Bases: Partially ionize, e.g., NH_3(aq) + H₂O_(l) ⇌ NH₄⁺_(aq) + OH^-_(aq).

Interference with enzyme activity: Low pH disrupts metabolic processes.
Damage to gills and skin: Acidic water irritates sensitive tissues.
Aluminum toxicity: Leached aluminum from soil affects respiration and osmoregulation in fish.
Disruption of food chains: Impacts plankton populations, affecting aquatic ecosystems.

Colour Change: The blue colour of copper sulfate fades, and reddish-brown copper forms on the iron.

Temperature Change: The reaction is exothermic, releasing heat.

Precipitate Formed: A white precipitate of silver chloride (AgCl).

Explanation of the Sneezing Reflex Pathway:

1. Stimulus: An irritant, such as dust or pollen, enters the nasal passage.
2. Receptor: Sensory neurons in the nose detect the irritant.
3. Relay Neuron: The sensory neurons send signals to the spinal cord, bypassing the brain for faster response.
4. Motor Neuron: Relay neurons transmit the signal to motor neurons.
5. Effector: Motor neurons signal effector muscles, like abdominal muscles and the diaphragm.
6. Response: The muscles contract forcefully, resulting in a sneeze.

Example: Coleus, Croton, Prayer Plant.

When a leaf is boiled in alcohol, chlorophyll dissolves into the alcohol, leaving the leaf decolorized and the solution green.

Why chlorophyll is necessary: Chlorophyll absorbs light energy, primarily from the red and blue regions of visible light, to drive the light-dependent reactions of photosynthesis. These reactions produce ATP and NADPH, which are then used in the Calvin cycle to convert CO₂ into glucose. This glucose is stored as starch for long-term storage without affecting osmotic balance.

Impact on Plants: Without deer grazing, plant populations will increase.
Impact on Lions: Lions would face food shortages and their population would decline or go extinct.
In a Food Web: Lions might switch to alternate prey, reducing the impact on their population compared to a food chain.

Chemical Linked to Ozone Depletion: Chlorofluorocarbons (CFCs).
International Measure: The Montreal Protocol (1987) phased out CFC production and consumption to protect the ozone layer.

Ray Diagram:

Cause of Dispersion: Each wavelength of light has a different refractive index in the prism, causing them to refract at different angles and separate into a spectrum.
Highest Refractive Index: Violet light bends the most and has the highest refractive index due to its shortest wavelength.

Given:
Power of oven (P) = 2000 W
Voltage (V) = 220 V
Current rating of circuit (I_circuit) = 5 A
Calculation:
I_oven = P / V = 2000 W / 220 V = 9.1 A
Expected Result: The oven draws more current than the circuit can handle, causing the fuse to blow. The oven will not work.

Ethanol is oxidized to ethanoic acid in the presence of acidified potassium dichromate. This is an oxidation reaction as ethanol gains oxygen.

This is a neutralization reaction where ethanoic acid reacts with sodium hydroxide to form sodium ethanoate and water.

This reaction produces soap (sodium salt of fatty acid) and glycerol.

Soap molecules form micelles, with hydrophobic tails dissolving grease and hydrophilic heads interacting with water, allowing the grease to be washed away.

Where P is power, V is potential difference, and R is resistance. Using Ohm’s law (V = IR), power can also be expressed as P = VI or P = I2R.

Given: Voltage (V) = 220 V, Energy consumed (E) = 11 kWh = 11000 Wh, Time (t) = 5 hours.
P = 11000 / 5 = 2200 W = 2.2 kW.

I = 2200 W / 220 V = 10 A.

R = 2202 / 2200 = 48400 / 2200 = 22 Ω.

Where R is resistance (Ω), l is length (m), and A is cross-sectional area (m²). The SI unit of resistivity (ρ) is ohm-meter (Ω·m).

Given: Length (l) = 3 m, Resistance (R) = 60 Ω, Area (A) = 4 × 10^-7 m².
ρ = (60 × 4 × 10-7) / 3 = 8 × 10-7 Ω·m.

Stretching the wire doubles its length and reduces its cross-sectional area, but resistivity (ρ) depends only on the material composition and remains unaffected.