Explanation

• Hydrogen (H2) and Argon is not a greenhouse gas.
• Greenhouse gases are gases that trap heat in Earth’s atmosphere and cause the Greenhouse Effect.

The main greenhouse gases are:

• Carbon dioxide (CO2)
• Methane (CH4)
• Nitrous oxide (N2O)
• Water vapor (H2O)
• Ozone (O3)
• Chlorofluorocarbons (CFCs)
• Hydrofluorocarbons (HFCs)
• Perfluorocarbons (PFCs)

Last verified on 01-05-2026

Explanation

• The chemical name of chalk is Calcium carbonate.
• Its chemical formula is CaCO₃.
• It is a soft, white mineral.
• Commonly used in blackboard chalk and limestone.
• Found naturally in rocks and marine shells.

Last verified on 30-04-2026

Explanation

• Evaporation is the process of liquid changing into vapor.
• During this process, heat is absorbed from the surroundings.
• This causes a drop in temperature (cooling effect).
• That is why sweating cools the human body.
• Evaporation is a natural cooling phenomenon.

Last verified on 26-04-2026

Explanation

• Roentgen rays are also called X-rays.
• They are used to detect fractures and bone diseases.
• They pass through soft tissues but not bones clearly.
• Doctors use them in medical imaging (radiology).
• They were discovered by Wilhelm Roentgen.

Last verified on 26-04-2026

Explanation

• Washing soda is also known as sodium carbonate (Na2CO3).
• It is used to remove permanent hardness of water.
• Permanent hardness is caused by the presence of magnesium and calcium sulfates or chlorides in water, which cannot be removed by boiling.
• Washing soda helps to precipitate these minerals, making the water softer.

Last verified on 23-04-2026

Explanation

• Metals that do not oxidize or corrode easily are called noble metals.
• These metals are characterized by their high resistance to oxidation and corrosion in moist air, owing to their very low reactivity.
• Examples: Gold (Au), Platinum (Pt), Palladium (Pd), Rhodium (Rh), Iridium (Ir), Osmium (Os), Ruthenium (Ru), and often Silver (Ag)

Last updated by NS 19 April 2026

Explanation

• Carbonated water contains carbon dioxide (CO₂) dissolved in water.
• The gas is dissolved under high pressure.
• It forms weak carbonic acid (H₂CO₃).
• This gives fizzy drinks their bubbles.
• So, it is carbon (CO₂) in water under high pressure.

Last verified on 12-04-2026

Explanation

• Kc (equilibrium constant) depends on temperature.
• In endothermic reactions, heat is absorbed.
• Increasing temperature shifts equilibrium forward.
• This increases the value of Kc.
• Therefore, Kc is directly proportional to temperature in endothermic reactions.

Last verified on 12-04-2026

Explanation

• An acidic buffer consists of a weak acid + its salt (conjugate base).
• This combination resists changes in pH.
• HCN (weak acid) + NaCN (its salt) fits this definition.

Last verified on 12-04-2026

Explanation

• In thermodynamics, a system is the part under study.
• Everything outside it is called surroundings.
• Here, the focus is on the gas behavior.
• So, the O₂ gas inside the balloon is the system.
• Freezer and environment act as surroundings.

Last verified on 12-04-2026