Explain why BeH₂ molecule has a zero dipole moment although the Be–H bonds are polar.

The mass of an electron is 9.1 × 10^–31 kg. If its K.E. is 3.0 × 10^–25 J, calculate its wavelength.

Calculate the amount of carbon dioxide that could be produced when

(i) 1 mole of carbon is burnt in air.

(ii) 1 mole of carbon is burnt in 16 g of dioxygen.

(iii) 2 moles of carbon are burnt in 16 g of dioxygen.

Calculate the wavelength of an electron moving with a velocity of 2.05 × 10⁷ ms^–1.

Balance the following redox reactions by ion – electron method :

(a) MnO₄ ^– (aq) + I ^– (aq) → MnO_{2 (s)} + I_2(s) (in basic medium)

(b) MnO₄ ^– (aq) + SO_{2 (g)} → Mn²⁺ (aq) + HSO₄^– (aq) (in acidic solution)

(c) H₂O_{2 (aq)} + Fe ²⁺ (aq) → Fe³⁺ (aq) + H₂O (l) (in acidic solution)

(d) Cr₂O₇ ^2– + SO_2(g) → Cr³⁺ _(aq) + SO₄^2– (aq) (in acidic solution)

In a process, 701 J of heat is absorbed by a system and 394 J ofwork is done by the system. What is the change in internal energy for the process?

What will be the minimum pressure required to compress 500 dm³ of air at 1 bar to 200 dm³ at 30°C?

In a reaction A + B2 → AB2 Identify the limiting reagent, if any, in the following reaction mixtures.

(i) 300 atoms of A + 200 molecules of B

(ii) 2 mol A + 3 mol B

(iii) 100 atoms of A + 100 molecules of B

(iv) 5 mol A + 2.5 mol B

(v) 2.5 mol A + 5 mol B

At 0°C, the density of a certain oxide of a gas at 2 bar is same as that of dinitrogen at 5 bar. What is the molecular mass of the oxide?

Which one of the following will have largest number of atoms?

(i) 1 g Au (s)

(ii) 1 g Na (s)

(iii) 1 g Li (s)

(iv) 1 g of Cl2(g)

Density of a gas is found to be 5.46 g/dm³ at 27 °C at 2 bar pressure. What will be its density at STP?

Identify the functional groups in the following compounds

Comment on the thermodynamic stability of NO(g), given

1/2 N₂(g) + 1/2 O₂(g) → NO(g) ; Δ_rH⁰ = 90 kJ mol^–1

NO(g) + 1/2 O₂(g) → NO₂(g) : Δ_rH⁰= –74 kJ mol^–1

Symbols can be written, whereas symbols  are not acceptable. Answer briefly.

Considering x-axis as the internuclear axis which out of the following will not form a sigma bond and why?

(a) 1s and 1s

(b) 1s and 2p_x

(c) 2p_y and 2p_y

(d) 1s and 2s.

What is the wavelength of light emitted when the electron in a hydrogen atom undergoes transition from an energy level with n = 4 to an energy level with n = 2?

Find energy of each of the photons which

(i) correspond to light of frequency 3× 1015 Hz.

(ii) have wavelength of 0.50 Å.

Suggest a list of the substances where carbon can exhibit oxidation states from -4 to +4 and nitrogen from -3 to +5.

Write the complete symbol for the atom with the given atomic number (Z) and Atomic mass (A)

(i) Z = 17, A = 35

(ii) Z = 92, A = 233

(iii) Z = 4, A = 9

A 0.02 M solution of pyridinium hydrochloride has pH = 3.44. Calculate the ionization constant of pyridine

Calculate the total pressure in a mixture of 8 g of dioxygen and 4 g of dihydrogen confined in a vessel of 1 dm³ at 27°C. R = 0.083 bar dm³ K^–1 mol^–1.