The correct option is 10-7 to 10-10 m.

EXPLANATION:

Colloids:

• it is a heterogenous mixer of small particle which is dispersed throughout the solution. examples are- Milk, blood, soap, etc.
• Colloids have a particle size range between 10-7 to 10-10 m.
• A colloid is a heterogeneous mixture in which one substance is dispersed (dispersed phase) as very fine particles in another substance called a dispersion medium.
• Based on the nature of the interaction between the dispersed phase and dispersed medium, the colloids are classified into Lyophilic colloids and Lyophobic colloids.
• The process by which we agitate the colloidal particles into large size particles so they can be precipitated is called coagulation.

Additional Information

Classification of colloids based on the type of phases:

• The colloidal system is heterogeneous in nature and consists of two phases called the dispersion medium and the dispersed phase.
• The component that is present in a small amount and behaves like a solute is called the dispersed phase and the component present in excess is called the dispersion medium.
• Depending on the nature of the dispersed phase and dispersion medium, colloids can be classified as:​

The correct answer is option 2.

Key Points

Corrosion:

• Corrosion refers to the degradation of metals by the action of air, moisture, or a chemical on their surface.
• The reaction of iron and oxygen forms an iron oxide which is a reddish-brown oxide.
• This is called Rust or corrosion of iron metal.
• This reaction happens only in presence of oxygen and moisture.
• The presence of impurities like Moisture, Acid, salt, Temperature, Presence of acid, etc. is some factor that affects corrosion.
• Here is the chemical reaction of Rust:
  • Fe²⁺ + 3O₂ → 2Fe₂O₃
  • Fe₂O₃ + xH₂O → Fe₂O₃. xH₂O (rust)

Blackening of Silver:

• Silver is a highly unreactive metal so it does not react with the oxygen of air easily.
• But air usually contains little sulfur compounds such as hydrogen sulfide gas (H₂S). 
• So, the silver objects combine slowly with the H2S gas present in the air to form a black coating of silver sulfide (Ag2S).
• Therefore, the shining silver coins and silver ornaments become tarnished or gradually turn black due to the formation of a thin layer of silver sulfide layer on their surface by the action of  H2S gas present in the air. Hence option 2 is correct.

Additional Information

• Corrosion can be prevented using the following methods-

1. Electroplating
2. Cathodic Protection
3. Galvanization
4. Painting and Greasing
5. Using corrosion inhibitor

Reactivity series:

The correct option is option 1.

Key Points

Chemical Reaction:

• A more reactive metal like aluminium can also be used as a reducing agent in the extraction of metals from their oxides.
• Aluminium is used as a reducing agent where the metal oxide is of a comparatively more reactive metal than zinc, etc. 
• The oxides of manganese and chromium metals are not satisfactorily reduced by carbon.
• So, manganese and chromium metals are extracted by the reduction of their oxides with aluminium powder.
• The aluminium powder reduces the metal oxide to metal and is itself oxidised to aluminium oxide. 
• Manganese metal is extracted by the reduction of its oxide with aluminium powder as the reducing agent.
• When manganese dioxide is heated with aluminium powder, then manganese metal is produced, and the reaction is 

3M_nO₂(s) + 4AI(s)→ 3Mn(l) + 2Al₂​O₃(s) + Heat

• From the above reaction, it is clear that the reduction of manganese dioxide with aluminium is a highly exothermic reaction. Hence option 1 is correct.
• A lot of heat is evolved during the reduction of manganese dioxide with aluminium powder because of which the manganese metal produced is in the molten state (or liquid state).

The correct answer is 10.

Key Points

• Number of protons in an atom = Z
• Number of electrons in an atom = Z
• Number of nucleons in an atom = A
• Number of neutrons in an atom = N = A – Z
• Hence for X 
  • Z = 8
  • A = 18
  • No of neutrons = A – Z = 10

Additional Information

• ATOMIC NUMBER: It is defined as the number of protons present in the nucleus. It is denoted by letter Z.
• MASS NUMBER: The total number of protons and neutrons present in a nucleus is called the mass number of the element. It is denoted by letter A.

The correct answer is Three pairs only

Key Points

Indicator:

• A chemical indicator is a material that gives a signal of the presence or absence of chemical species such as an acid or basic in a solution.
• It gives an indication by changing the color.
• When are present in an acidic and basic solution, they undergo a physical change. 
• Chemical indicators are categorized into two categories:
  • Natural indicator
  • Artificial indicator
• Litmus, red cabbage, turmeric, and china rose are Natural Indicators because they are found in nature.
• Artificial indicators are compounds prepared in a lab like Phenolphthalein and Methyl Orange

• Hence option 3 is correct.

Concept:

Solute and Solvent:

• When one substance dissolves into another, a solution is formed.
• A solution is a homogeneous mixture consisting of a solute dissolved into a solvent.
• The solute is the substance that is being dissolved, while the solvent is the dissolving medium.
• Mass % = [(Mass of solute)/(Mass of solution)] × 100 

Calculation:

Given that, 

Mass of solution (A) = 2 g

Mass of solvent (water) = 18 g

We know that,

Mass % = [Mass of A / Mass of solution] × 100

⇒ Mass % = [2 g/(2 g of A + 18 g of water)] × 100 

⇒ Mass % = (2/20) × 100 = 10 %

∴ The mass percent of the solute is 10%

The correct answer is Acid rain.

Key Points

• Sulfur dioxide and nitrogen oxides combine with water molecules in the air to form Acid rain.
• Acid rain, or acid deposition, is a broad term that includes any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. 
• Acid rain results when sulfur dioxide (SO₂) and nitrogen oxides (NOX) are emitted into the atmosphere and transported by wind and air currents.

Additional Information

• The major sources of SO₂ and NOX in the atmosphere are:
• Burning of fossil fuels to generate electricity. Two thirds of SO₂ and one fourth of NOX in the atmosphere come from electric power generators, vehicles, heavy equipment, manufacturing, oil refineries and other industries.

The correct answer is Baking soda.

Key Points

• Baking soda
  • It has no water of crystallization.
  • It is also known as Sodium bicarbonate with the chemical formula NaHCO₃.
  • It is commonly used in the kitchen for cooking a variety of food.
  • It is used in baking food items like cakes, cookies, etc.
  • It can be used as a neutralizer or antacid to quickly relieve stomach acidity.

Important Points

• Gypsum
  • ​It is composed of Calcium sulfate (CaSO₄) and water (H₂O).
  • ​Its chemical name is calcium sulfate dihydrate (CaSO₄. 2H₂O).
  • It is mined from sedimentary rock formations around the world.
  • It helps in controlling the rate of hardening of the cement.
  • Plaster of Paris is made up of quick-setting gypsum. 
• Blue vitriol
  • ​It is chemically called Copper Sulphate.
  • The formula is CuSO₄·5H₂O.
  • It is a versatile chemical with an extensive range of uses in industry and agriculture.
  • It is used as a fungicide, algaecide, root killer, and herbicide.
  • Vitriol generally encompasses sulfates of certain metals like Iron, Copper, Magnesium, etc.
• Washing soda
  • Its chemical name is sodium carbonate (Na₂CO₃·10H₂O).
  • It is used in the glass, soap, and paper industries.
  • It is also used to remove the permanent hardness of the water.

The correct answer is Cetyltrimethyl ammonium bromide.

Key Points

• Cetyltrimethyl ammonium bromide is a cationic detergent.
• ​Cationic detergents
  • These are quaternary ammonium salts of amines with anions as acetates, chlorides, or bromides.
  • The cationic part consists of a long hydrocarbon chain and a positive charge Nitrogen atom.
  • It contains a hydrophobic component of quaternary ammonium as the polar end and the ammonium center are positively charged.
  • The purpose is to neutralize the static electrical charges from residual anionic (negative ions) detergent molecules
• Examples of cationic detergents are quaternary ammonium compounds, benzalkonium chloride, and cetyltrimethyl ammonium bromide.

The correct answer is Only (I) and (II).

Key Points

• Dalton's atomic theory
  • All matter is made up of tiny, indivisible particles called atoms.
  • All atoms of a specific element are identical in mass, size, and other properties. However, atoms of different elements exhibit different properties and vary in mass and size.
  • Atoms can neither be created nor destroyed. Furthermore, atoms cannot be divided into smaller particles.
  • Atoms of different elements can combine in fixed whole-number ratios to form compounds.
  • Atoms can be rearranged, combined, or separated in chemical reactions.
  • The relative number and kinds of atoms are constant in a given compound.
  • Dalton based his theory on the law of conservation of mass and the law of constant composition.

Additional Information

• Limitations of Dalton's Atomic Theory:
  • Atoms consist of particles like electrons, protons, and neutrons but Dalton said atoms are indivisible and can neither be created nor be destroyed.
  • The Discovery of isotopes revealed that the atoms of the same element possess different weights.