Explanation

• Acids react with carbonates to produce salt, water and carbon dioxide gas.
• Effervescence (bubbling) occurs due to the release of carbon dioxide.
• Example: Hydrochloric acid reacts with calcium carbonate to form calcium chloride, water and carbon dioxide.

Last verified on 07-11-2026

Explanation

• Hydrogen attached to fluorine can form a hydrogen bond with the lone pair of nitrogen in NH₃.
• Hydrogen bonding is an intermolecular attraction.
• It is stronger than many ordinary dipole interactions.

Last verified on 06-11-2026

Explanation

• Oxygen shares electrons with two hydrogen atoms.
• The O–H bonds are polar covalent bonds.
• Hydrogen bonding occurs between separate water molecules.

Last verified on 06-11-2026

Explanation

Water molecules are held together by hydrogen bonds,

It is a type of strong intermolecular force

Where the slightly positive hydrogen of one molecule attracts the slightly negative oxygen of another, creating a "sticky" network that gives water unique properties like surface tension.

Explanation

• Chlorine has atomic number 17.
• Its electronic configuration is 2, 8, 7.
• Seven valence electrons place it in Group 17, while three electron shells place it in Period 3.

Last verified on 06-11-2026

Explanation

• Sodium has atomic number 11, so it contains 11 protons.
• Neutrons = Mass number − Atomic number = 23 − 11 = 12.
• A neutral sodium atom has 11 electrons.

Last verified on 06-11-2026

Explanation

• Wilhelm Conrad Rontgen discovered X-rays
• He was discovered on 8 November 1895.
• He got the Nobel Prize in Physics in 1901.

Additional questions

• The penetrating power of X-rays depends on their frequency

Last updated by NA on 05-11-2026

Explanation

• Copper sulphate pentahydrate contains five molecules of water of crystallization.
• Its crystals are characteristically bright blue due to the presence of hydrated copper(II) ions.
• On heating, it loses its water of crystallization and becomes white anhydrous copper sulphate (CuSO₄).
• Adding water to anhydrous copper sulphate restores its blue color.

Last verified on 02-11-2026

Explanation

• Hydrogenation is an addition reaction in which hydrogen converts benzene into cyclohexane under suitable conditions.
• Benzene commonly undergoes electrophilic substitution reactions in which a hydrogen atom is replaced by an electrophile.
• Halogenation: A hydrogen atom is replaced by chlorine or bromine.
• Nitration: A nitro group (–NO₂) is introduced into the benzene ring.
• Sulphonation: A sulphonic acid group (–SO₃H) is introduced.

Last verified on 02-11-2026

Explanation

• Molecular shape: Long or irregular molecules generally have greater viscosity due to stronger intermolecular interactions and entanglement.
• Temperature: The viscosity of liquids generally decreases when temperature increases.
• Molecular size: Larger molecules often have greater viscosity because of stronger intermolecular forces and greater resistance to flow.
• Therefore, molecular shape, temperature and molecular size all affect the viscosity of liquids.

Last verified on 02-11-2026