Which unit is used to measure the atomic radius? Convert it into metre.

Name the smallest particle of an element that can retain all the chemical properties.

Why is it not possible to see an atom with the unaided eyes?

Write the formula of lead phosphate.

What is meant by the valency of an element?

What helps in determining the formula of an ionic compound?

What is meant by molar mass?

What is meant by the law of conservation of mass? If 12 g of C is burnt in the presence of O₂, how much CO₂ will be formed?

[Atomic mass of C = 12 u, O = 16 u]

Calculate the formula mass of CuSO₄.5H₂O.

[Atomic mass of Cu = 63.5 u, S = 32 u, O = 16 u, H = 1 u]

Calculate the number of moles in 52 g of He.

[Atomic mass of He = 4 u]

Convert 12.044 × 10²³ number of He atoms into number of moles.

Calculate the mass of 0.5 mole of N₂ gas.

[Atomic mass of N = 14 u]

Calculate the mass of 0.5 mole of N atoms.

Calculate the mass of 3.011 × 10²³ atoms of nitrogen.

Calculate the mass of 6.022 × 10²³ N₂ molecules.

Give postulates of Dalton’s atomic theory.

Write the chemical formula using criss-cross method:

(a) Ammonium sulphate

(b) Magnesium bicarbonate

(c) Barium nitrate

(a) Define the term ‘molecular mass’.

(b) Determine the molecular mass of ZnSO₄.

[Atomic mass of Zn = 65 u, S = 32 u, O = 16 u]

With the help of example, explain the law of conservation of mass.

Calculate:

(a) The number of moles of Sulphur (S₈) present in 16 g of solid sulphur.

(b) the mass of 10 moles of sodium sulphite (Na₂SO₃).

(c) the number of atoms in 11.5 g of Na.

[atomic mass: Na = 23u; S = 32u, O = 16u, N_A = 6.022 × 10²³ mol^–1]

Calculate:

(a) the mass of 1.0505 × 10²³ molecules of carbon dioxide (CO₂).

(b) the number of molecules of 0.25 moles of NH₃,

(c) the formula unit mass of Na₂SO₃.

[Atomic mass: Na = 23 u, S = 32 u, O = 16 u, H = 1 u, N_A = 6.022 × 10²³ mol^–1]

What is meant by the term ‘mole’? Calculate the number of moles in

(a) 3.011 × 10²³ atoms of C

(b) 32 g of oxygen gas

[N_A = 6.022 × 10²³ mol^–1, At. mass of O = 16 u and C = 12 u]

(a) Calculate the number of moles in 112 g of iron.

(b) Calculate the mass of 0.5 mole of sugar (C₁₂H₂₂O₁₁).

[Atomic mass of Fe = 56 u, C = 12 u, H = 1 u, O = 16 u]

Define the following terms

(a) Atom

(b) Molecule

(c) Avogadro’s number

(d) Valency

(e) Molar mass