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In agricultural practices, instead of fertilizers, manures should be commonly employed because continuous use of fertilizers in an area can destroy soil fertility as the organic matter in the soil is not replenished. It also affects various microorganisms present in the soil which are beneficial for maintaining soil quality. Disrupting the nature of soil will hamper in the production of crop.

Due to larger size of La³⁺ as compared to Lu³⁺, it has a greater ionic character hence gives more no. of –OH ions.

(a) Due to lanthanoid contraction, the size of Lu³⁺ is smaller than that of La³⁺ ion. Thus, Lu-OH bond is stronger than La-OH bond. Hence, La(OH)₃ is stronger base than Lu(OH)₃. 

(b) This is due to comparable energies of 5f,6d and 7s orbital in actinoids 

(c) This is due to poor shielding effect by 5f electrons in actinoid as compared to that by 4f electron in the lanthanoids. 

(i) It takes place in three steps:

Conversion of chromite ore into sodium chromate

4FeCr₂O₄ + 4Na₂CO₃ + 7O₂  → Na₂CrO₄ + Fe₂O₃ + 8CO₂

Conversion of sodium chromate into sodium dichromate

2Na₂CrO₄ + 2H⁺ →  Na₂Cr₂O₇ + 2Na⁺ + H₂O

Conversion of sodium dichromate into potassium dichromate

Na₂Cr₂O₇ + 2KCl → K₂ Cr₂O₇ + 2NaCl

The melting point of ice as well as the boiling point of water changes with change in pressure. The presence of impurities also changes the melting and boiling points. However the triple point of water has a unique temperature and is independent of external factors. It is that temperatures at which water, ice & water vapour co-exist that is 273. 16 K and pressure 0.46 cm of Hg.

(d) Ignition temperature

(iv) ionic solid with [PCl₄]⁺ tetrahedral and [PCl₆]^– octahedra

PCl₅ exist as [PCl₄]⁺ [PCl₆] ^- in solid state hence it is ionic.

Due to decrease in electron density due to increase in atomic size.

Due to inert pair effect in Bi.

a. The chemical name and formula of the white coloured powder which is used by doctors for supporting fractured bones is: - 

Chemical name – Calcium sulphate hemihydrate 

Formula - CaSO₄ \(\frac12\)H₂O 

b. When this white powder is mixed with water a hard-solid mass is obtained. The balanced chemical equation for the change is: -

CaSO₄.\(\frac12\)H₂O + 1\(\frac12\)H₂O → CaSO₄.2H₂O

Correct option is d. one sigma, two pi

The disadvantage of broad spectrum antibiotics is that they also kill the useful bacteria in the alimentary canal.

Narrow spectrum antibiotics are effective against a single organism or disease and referred to as limited spectrum antibiotics, e.g., penicillin G.

Narrow Spectrum Antibiotics are specially designed for targeting a particular harmful bacteria or organisms. The conventional antibiotics often cause harm to the good organism(good bacteria) of our body. To minimise these, the study was performed to identify the unique nature of disease-causing agents and target them specifically using these narrow-spectrum drugs. Example-Ampicillin

Correct Option  (d) 100% and 0%

Explanation: 

1. Based on (n+l) values energy value of 3d orbitals is 3 + 2 = 5, energy value of 4s orbitals is 4 + 0 = 4 

2. The energy level of 4s orbital is less than the 3d orbital according to the Aufbau principle electron enters into lower energy orbital first. 

3. Thats why electrons enters into 4s orbital after filling 3p, but not into 3d.

Since, maximum frequency 4 corresponds to 125, then mode = 125

Given: Total surface area of a cone = 616 sq.cm., 

slant height of the cone is three times the radius of its base 

To find: Slant height (l) 

Solution:

i. Let the radius of base be r cm. 

∴ Slant height (l) = 3r cm 

Total surface area of cone = πr (l + r) 

∴ 616 = πr(l + r) 

∴ 616 = \(\sqrt[22]7\) x r x (3r + r) 

∴ 616 = \(\sqrt[22]7\) x 4r²

∴  r^{2 = \(\frac{616\,\times\,7}{22 \,\times\,4}\)}

 ^{= \(\frac{28\,\times\,7}{4}\)}

∴ r² = 49 

∴ r = \(\sqrt{49}\)… [Taking square root on both sides] 

= 7 

ii. Slant height (l) = 3r = 3 x 7 = 21 cm 

∴ The slant height of the cone is 21 cm.

1. b) 45°

2. a) 25.24 m

3. a) 20√3 m

4. b) 45°

5. a) corresponding angle

It is used in oceanography in calculating the height of tides in oceans. The sine and cosine functions are fundamental to the theory of periodic functions, those that describe the sound and light waves. Calculus is made up of Trigonometry and Algebra.

Fleming’s left hand rule. According to it, if we stretch forefinger, central finger and the thumb of our left hand mutually perpendicular to each other such that the forefinger indicates the direction of the magnetic field and the central finger indicates the direction of current, then the thumb will indicate the direction of force on the conductor.

The process of converting a material into a magnet is called magnetizing.

Once magnetized the material is capable of exhibiting magnetic properties.

Two examples in daily life:

1. Earthing

2. Lightning

Cloud to ground lightning discharges 30,000 amperes and up to 100 million volts and emits light, X rays, radio waves and even gamma rays. Plasma temperature in lightning can approach 28000 K and electron densities may exceed 10²⁴ /m³ . So it not easy to use this charge as electricity.

Being ‘modern’ cannot be limited to only using modern devices or gadgets but there should be a willingness to receive new ideas.

Threshold frequency of a metal is the minimum cut-off frequency of incident light below which no photoelectric emission takes place irrespective of intensity of incident light. 

Threshold frequency of a metal is the minimum cut-off frequency of incident light below which no photoelectric emission takes place irrespective of intensity of incident light, photoelectric current is directly proportional to intensity of incident light.

An earthquake affects the atmosphere by creating amounts of debris and dust which will add to the air that we breathe. Earthquakes can also trigger volcanoes which will release tonnes of ashes and other debris into the atmosphere. This can sometimes cause the blocking out of the sun, air pollution and are increased amount of carbon in the air.

Correct option is B) concave

V₀ = 1.5 V
∴ Maximum kinetic energy of the emitted electrons,

\(\frac{1}{2}mV^2_{max} = eV_0= 1.5j= 15eV\)

i. – (b) 

ii. – (a)

It is the Parsec is the distance at which average radius of earth's orbit subtends an angle of 1 are second.

1 Parsec = 3.008 x 10¹⁶ m.

E₂/E₁ = [ T₂/T₁]⁴ = [(2227 + 273) / (727 + 273)]⁴ = [2500/1000]⁴ = 39

A blanket encloses air layer in its pores and fur which prevents heat from outside to come in contact with the ice and melt it

From Stefan’s law of radiation, the amount of heat radiated per second is E = σT⁴.

E = 5.67 × 10^-8 × (2000)⁴

= 5.67 × 2⁴ × 10⁴

= 5.67 × 16 × 10⁴

= 9.072 × 10⁵Js^-1.

If e is the emissivity of the surface, then the heat radiated per second R¹ = eR

= 0.37 × 9.072 × 10⁵

= 3.35 × 10⁵ Js^-1.

No, the bomber will not hit the target. It is because at the time bomb is released, it has the same horizontal velocity as the bomber. Due to its horizontal velocity, say v, it will fall a distance v√(2h/g) ahead of the target, where h is the height of bomber.

We usually see that the size of naphthalene balls decrease gradually and finally disappeared when they are kept in open. This happens because of sublimation of naphthalene. Naphthalene balls are used in toilets also as disinfectant and air freshener.

Ten tube-wells are too much for a lane of fifty houses, this can lead people to mindlessly exploit the groundwater. This can lead to depletion of the water table in the long run.

Hint:
Water present underground; well, lake, pond, spring, hand pump, etc

(a) A pukka floor

(b) water table. 

The rainwater and water from other sources such as rivers and ponds seeps through the soil and fills the empty spaces and cracks deep below the ground. The process of seeping of water into the ground is called infiltration. By the process of infiltration, groundwater gets recharged.

(a) The freshwater stored in the ground is much more than that present in the rivers and lakes of the world. (T)
(b) Water shortage is a problem faced only by people living in rural areas. (F)
(c) Water from rivers is the only source for irrigation in the fields. (F)
(d) Rain is the ultimate source of water. (T)

The time of sunrise and sunset, wind flow, percentage rainfall in that area should be taken into consideration to estimate the type of weather in that given area.

Thermometer: An instrument for measuring temperature, especially one having a graduated glass tube with a bulb containing a liquid, typically mercury or colored alcohol, that expands and rises in the tube as the temperature increases.

Plowing: A farm implement consisting of a heavy blade at the end of a beam, usually hitched to a draft team or motor vehicle and used for breaking up soil and cutting furrows in preparation for sowing.