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

Explanation

• A covalent bond forms when atoms share electrons.
• It usually occurs between non-metals.
• Sharing helps atoms achieve stable electron configuration.
• No transfer of electrons occurs.
• Therefore, it is based on electron sharing.

Last verified on 12-04-2026

Explanation

• Bond energy, length, and order describe how strong a chemical bond is.
• Higher bond energy → stronger bond.
• Shorter bond length → stronger bond.
• Higher bond order → stronger bond.
• All three parameters indicate bond strength.

Last verified on 12-04-2026

Explanation

Rate ∝ ^n

If × 4 → Rate × 2:[Reactant]

4ⁿ = 2 → n = 1/2

Last verified on 12-04-2026

Explanation

• Carbon is a tetravalent element.
• It forms 4 covalent bonds in most compounds.
• In C₂H₆O (ethanol or dimethyl ether), carbon still makes 4 bonds.
• Valency is based on bonding capacity, not charge here.
• So, carbon’s valency remains 4.

Last verified on 12-04-2026

Explanation

Use the first law of thermodynamics: ΔU = Q + W

Sign convention:  

Heat added _to_ system: Q = +20 kJ

Work done _on_ system: W = +60 kJ

ΔU = 20 + 60 = 80 kJ

Last verified on 12-04-2026