ICSE Class 10 Chemistry Syllabus

List three examples of compounds containing a coordinate bond.

Ammonium ion (NH4+), hydronium ion (H3O+), and ozone (O3) (also Al2Cl6).

Why do ionic compounds have high melting and boiling points?

Strong electrostatic forces of attraction between oppositely charged ions require a large amount of energy to break.

Why do ionic compounds conduct electricity in molten or aqueous state but not in solid state?

In molten/aqueous state ions are free to move and carry charge; in solid state ions are fixed in the lattice and cannot move.

Why are covalent compounds generally poor conductors of electricity?

They consist of neutral molecules and do not contain free ions or electrons to carry charge.

Compare solubility of ionic and covalent compounds.

Ionic compounds are generally soluble in water (polar solvents) but insoluble in organic solvents; covalent compounds are generally insoluble in water but soluble in organic solvents.

Write the electron-dot (Lewis) structure description for the formation of sodium chloride (NaCl).

Na (2,8,1) loses 1 electron to become Na+ (2,8); Cl (2,8,7) gains it to become Cl- (2,8,8); the ions attract to form NaCl.

Why is the bond in HCl polar covalent?

Chlorine is more electronegative than hydrogen, so the shared electron pair is pulled toward Cl, giving it a partial negative charge and H a partial positive charge.

Define an acid according to the modern (Arrhenius) concept.

An acid is a substance that produces hydrogen ions (H+) / hydronium ions (H3O+) as the only positive ions when dissolved in water.

Define a base and an alkali.

A base is a substance that reacts with an acid to form salt and water; an alkali is a water-soluble base that produces hydroxide ions (OH-) in water.

What is the difference between a strong acid and a weak acid?

A strong acid ionises almost completely in water (e.g. HCl, H2SO4, HNO3); a weak acid ionises only partially (e.g. acetic acid, carbonic acid).

What is the action of acids and bases on litmus?

Acids turn blue litmus red; bases (alkalis) turn red litmus blue.

State the colours of methyl orange in acidic and basic solutions.

Methyl orange is red/pink in acid and yellow in alkali.

State the colours of phenolphthalein in acidic and basic solutions.

Phenolphthalein is colourless in acid (and neutral) and pink in alkali.

What is the pH scale and what do its values indicate?

A scale from 0 to 14 measuring acidity/alkalinity: pH < 7 is acidic, pH = 7 is neutral, pH > 7 is alkaline (basic).

What is a neutralisation reaction? Give its general equation.

The reaction of an acid with a base to form salt and water. General: Acid + Base → Salt + Water (e.g. HCl + NaOH → NaCl + H2O).

Define a normal salt, an acid salt, and a basic salt.

Normal salt: formed by complete replacement of acid's H with metal (NaCl). Acid salt: has replaceable H remaining (NaHSO4). Basic salt: contains OH or O along with the metal ion (Pb(OH)Cl).

What is an efflorescent substance? Give an example.

A substance that loses its water of crystallisation on exposure to air, e.g. washing soda (Na2CO3·10H2O).

What is a deliquescent substance? Give an example.

A substance that absorbs moisture from the air and dissolves in it, e.g. caustic soda (NaOH) or anhydrous CaCl2.

What is a hygroscopic substance? Give an example.

A substance that absorbs moisture from air without dissolving (no change of state), e.g. conc. sulphuric acid or quicklime (CaO).

What is water of crystallisation? Give an example with formula.

The fixed number of water molecules chemically combined in one formula unit of a crystalline salt, e.g. blue vitriol CuSO4·5H2O (5 molecules).

What colour precipitates do solutions of Cu2+, Fe2+, and Fe3+ give with sodium hydroxide?

Cu2+ gives a pale blue ppt; Fe2+ gives a dirty green ppt; Fe3+ gives a reddish-brown ppt.

What is observed when NH4OH (ammonium hydroxide) is added to a solution containing Cu2+ ions?

A pale blue precipitate forms first, which dissolves in excess to give a deep/inky blue solution (due to a complex).

What precipitate does a lead salt (Pb2+) form with sodium hydroxide, and what happens in excess?

A white precipitate of Pb(OH)2 forms, which dissolves in excess NaOH (being amphoteric).

How is the gas ammonia (NH3) identified in the lab?

It has a pungent smell, turns moist red litmus blue, and gives dense white fumes with a glass rod dipped in conc. HCl.

How is hydrogen chloride gas (HCl) identified?

It is pungent, turns moist blue litmus red, and gives dense white fumes with ammonia (a glass rod dipped in NH4OH).

State Avogadro's law.

Equal volumes of all gases, under the same conditions of temperature and pressure, contain an equal number of molecules.

What is the value of Avogadro's number?

6.022 × 10^23 (the number of particles in one mole).

What is molar volume (gram molecular volume) of a gas at STP?

22.4 litres (22,400 cm³) per mole at standard temperature and pressure.

Define relative molecular mass.

The number of times one molecule of a substance is heavier than 1/12th the mass of an atom of carbon-12 (numerically the sum of the atomic masses of all atoms in the molecule).

What is the relationship between number of moles, mass, and molar mass?

Number of moles = given mass / molar mass.

State Gay-Lussac's law of combining volumes.

When gases react, they do so in volumes which bear a simple whole-number ratio to one another and to the volumes of gaseous products, measured at the same temperature and pressure.