Explanation

• Wave speed is given by v = fλ.
• If speed remains constant, frequency and wavelength are inversely related.
• So, when frequency increases, wavelength decreases.
• If frequency is doubled, wavelength becomes half.
• This is a basic wave relation in physics.

Last verified on 12-04-2026

Explanation

• Work is defined as force × displacement.
• Force has dimensions MLT⁻².
• Displacement has dimension 𝐿.
• So, work = MLT⁻² × 𝐿 = ML²T⁻².

Last verified on 12-04-2026

Explanation

• Haber process is used to manufacture ammonia from nitrogen and hydrogen.
• Nitrogen is obtained from air, but hydrogen is usually obtained from natural gas or water, not both from air.
• Ammonia is formed as a compound.
• The reaction involves gases under high pressure and temperature.
• Therefore, the correct statement is about physical state of reactants and product.

Last verified on 12-04-2026

Explanation

• To obtain accurate results, precise measurement of mass and volume is essential.
• A balance is used to measure 2.5 g sodium carbonate accurately.
• A pipette measures 25.0 cm³ acid more accurately than a measuring cylinder.
• A thermometer is needed to record temperature change.
• Therefore, these three give the most accurate results.

Last verified on 12-04-2026

Explanation

• Powdered magnesium has a much larger surface area compared to magnesium ribbon.
• A greater surface area allows more collisions between magnesium and hydrochloric acid particles.
• This increases the frequency of successful collisions.
• Therefore, the reaction rate increases.
• So, powdered magnesium reacts faster than ribbon.

Last verified on 12-04-2026

Explanation

• Electronegativity is the ability of an atom to attract electrons in a bond.
• It increases across a period from left to right due to increasing nuclear charge.
• It decreases down a group because atomic size increases.
• Therefore, the correct trend is left to right in a period.

Last verified on 12-04-2026

Explanation

• Across a period, metallic character decreases from left to right.
• Magnesium is a metal, so it forms a basic oxide.
• Phosphorus and chlorine are non-metals, so they form acidic oxides.
• Therefore, Mg → basic, P → acidic, Cl → acidic oxides.

Last verified on 12-04-2026

Explanation

• Elements in the same group have similar chemical properties because they have the same number of valence electrons, not total electrons.
• They show similar reactions due to similar outer shell configuration.
• However, they differ in atomic (proton) number and mass number.
• Therefore, statement 2 and 3 are correct.

Last verified on 12-04-2026

Explanation

• A neutral salt is formed when a strong acid reacts with a strong base.
• It does not show acidic or basic nature in water.
• Its pH is approximately 7.
• It contains equal strength of acid and base ions.
• Example of neutral salt is NaCl (Sodium Chloride).

Last verified on 11-04-2026

Explanation

To get max Cr from Cr₂O₃, use the mass fraction of Cr in Cr₂O₃.

Molar mass Cr₂O₃ = 2(52) + 3(16) = 104 + 48 = 152 g/mol

Mass of Cr in 1 mol = 2(52) = 104 g

So Cr mass = 76g × (104/152) = 76 × 0.684 = 52g

Last verified on 11-04-2026