Sustainable development aims to meet current needs without compromising the ability of future generations to meet theirs. It balances:

1. Environmental Sustainability: Protecting natural resources and ecosystems.
2. Economic Sustainability: Ensuring equitable economic growth.
3. Social Sustainability: Improving quality of life and ensuring social equity.

Pressure (P) = 2 atm

Volume (V) = 410 ml = 0.410 L

Temperature (T) = 7ºC = 280 K

R = 0.082 L atm mol ⁻¹ K ⁻¹

Use the Ideal Gas Law: PV = (m/M) RT

⇒ M = RT\over mPV

⇒ M = 1  × 0.082 × 280\over 2 × 0.410

⇒ M = 28 g/mol

OR

Initial Pressure (P₁)= 1 atm

Initial volume (V₁) = 273 cm³

initial temperature (T₁) = 273 K (STP)

Final volume (V₂) = 300 cm³

Final temperature (T₂) = 300 K

From Combined Gas Equation: P_1V_1\over T_1 = P_2V_2\over T_2

P₂ = P_1V_1T_2\over T_1V_2

P₂ = 1 × 273 × 300\over 273 × 300 = 1 atm

Thus, the pressure is 1 atm.

The refractive index of a medium is a measure of how much the speed of light is reduced when it passes through the medium compared to its speed in a vacuum. It is defined as the ratio of the speed of light in a vacuum (c) to the speed of light in the medium (v):

n = c/v

OR

A convex lens is used to correct hyperopia (farsightedness). In this condition, the eye focuses light behind the retina instead of on it, causing distant objects to be seen more clearly than nearby objects. A convex lens converges the light rays, helping focus them correctly on the retina.

We are given that the current through r₁ ​ is 6 times the current through r₂ ​ when connected to the same potential difference.

Using Ohm’s Law:

I = V/R

Let the current through r₁ ​ be I₁ ​ and through r₂ ​ be  I₂ ​

According to the question,

I₁ = 6 × I₂

⇒ V/r₁ = 6 × V/r₂

⇒ 1/r₁ = 6 × 1/r₂

⇒ r₁/r₂ = 1/6

So, the ratio of r₁ and r₂ is 1 : 6

Kossel explained that an ionic bond forms due to the complete transfer of electrons from one atom (usually a metal) to another atom (usually a non-metal). This process leads to the formation of oppositely charged ions: the metal loses electrons to become a positively charged cation, and the non-metal gains electrons to become a negatively charged anion. The electrostatic attraction between these oppositely charged ions holds them together in an ionic bond.

OR

Liquid Hydrogen Chloride vs Molten Sodium Chloride in Conducting Electricity:

• Liquid hydrogen chloride (HCl) does not conduct electricity because, in its liquid form, HCl consists of neutral molecules. There are no free ions available to carry an electric current.
• Molten sodium chloride (NaCl) can conduct electricity because, when melted, the strong ionic bonds break, and the solid NaCl dissociates into free-moving Na⁺ and Cl⁻ ions. These free ions allow the molten NaCl to conduct electricity as they can move and carry the electric charge.

When ferric chloride reacts with aqueous ammonia, a reddish-brown precipitate of ferric hydroxide (Fe(OH)₃) forms.

Balanced chemical equation

FeCl₃ + 3NH₄OH → Fe(OH)₃ ↓ + 3NH₄Cl

When aluminium chloride (AlCl₃) reacts with aqueous ammonia, a white precipitate of aluminium hydroxide (Al(OH)₃) forms.

AlCl₃ + 3NH₄OH → Al(OH)₃ ↓ + 3NH₄Cl

Zinc blende (ZnS) can be called both a mineral and an ore of zinc because:

• Mineral: Zinc blende is called a mineral because it is a naturally occurring crystalline substance.
• Ore: Zinc blende is also classified as an ore of zinc because zinc can be economically extracted from it.

OR

Two ways to prevent the rusting of iron:

1. Galvanization: Coating iron or steel with a layer of zinc to protect it from rusting.
2. Painting or Coating: Applying a layer of paint or other protective coatings (such as plastic) on the iron surface to create a barrier against moisture and oxygen, thus preventing rust formation.

When methane (CH₄) is burnt in oxygen (O₂), it undergoes a combustion reaction, producing carbon dioxide (CO_₂), and water (H₂O), and releasing energy in the form of heat and light.

Balanced chemical equation

CH₄ ​+ 2O₂ ​→ CO₂ ​+ 2H₂​O

One use of each:

1. Acetic acid: It is used as a key ingredient in vinegar, which is commonly used in cooking and food preservation.
2. Ethyl alcohol (Ethanol): It is used in the preparation of alcoholic beverages.

The molar volume of a gas is the volume occupied by one mole of the gas at standard temperature and pressure.

Two reasons for the deviation are

Balanced Chemical Equation

Fe₂​O_3​ + 2Al → 2Fe + Al₂​O_3​

1 mole   54 g    111.6 g

Calculation of Aluminium

Quantity of Al required to produce 111.6 g of Fe = 54 g

∴ Quantity of Al required to produce 558 g of Fe

= 54\over 111.6 × 558

= 270 g

Calculation of mole of Fe₂O₃

Mole of Fe₂​O_3​ required to produce 111.6 g of Fe = 1 mole

∴ Mole of Fe₂​O_3​ required to produce 558 g of Fe = 1\over 111.6 × 558

= 5

OR

Balanced Chemical Equation:

2NH₄​Cl  + Ca(OH)₂​ → 2NH₃ ​+ CaCl₂ ​+ 2H₂​O

107 g             74 g               34 g       111g

Moles of NH₃ produced

Molar mass of NH₃ = 17 g

Mass of NH₃ = 10.2 g

Moles of NH₃ = 10.2/17 = 0.6

Volume of NH₃ at STP:

Volume = 0.6 × 22.4 = 13.44 L

Mass of Ca(OH)₂ Used:

Molar mass of Ca(OH)₂ = 74 g

From the equation, 1 mole Ca(OH)₂ produces 2 moles NH₃.

So for 0.6 moles NH₃:

Moles of Ca(OH)₂ = 0.6/2 = 0.3 moles

Mass of Ca(OH)₂ = 0.3 × 74 = 11.1 g

Summary

• Mass of Ca(OH)₂ used: 11.1 g
• Moles of NH₃ produced: 0.6 moles
• Volume of NH₃ at STP: 13.44 liters

The volume expansion coefficient (α) of a gas is defined as the fractional change in volume per unit change in temperature at constant pressure. Therefore, the quantity that remains fixed in this definition is:

Pressure (constant pressure is maintained).

Graphite, a form of carbon, is a non-metal that is an excellent conductor of heat.

OR

The linear expansion coefficient of copper, 17 × 10⁻⁶ °C⁻¹, means that for every 1°C rise in temperature, the length of a copper object increases by 17 × 10⁻⁶ times its original length. This describes how much a material expands per degree of temperature change.

A change of 1°C is equal to a change of 1 K, so the rate of expansion per unit temperature change is the same in both scales.