List of top Chemistry Questions

The longest wavelength doublet absorption transition is observed at 589 and 589.6 nm. Calculate the frequency of each transition and energy difference between two excited states.

Write Lewis dot symbols for atoms of the following elements: Mg, Na, B, O, N, Br.

In astronomical observations, signals observed from the distant stars are generally weak. If the photon detector receives a total of 3.15 × 10^–18 J from the radiations of 600 nm, calculate the number of photons received by the detector.

Explain why pure liquids and solids can be ignored while writing the equilibrium constant expression?

For the following equilibrium, \(K_c = 6.3 × 10^{14}\) at \(1000\  K\)
\(NO (g) + O_3 (g) ⇋ NO_2 (g) + O_2 (g)\)
Both the forward and reverse reactions in the equilibrium are elementary bimolecular reactions. What is \(K'_c\) for the reverse reaction?

Apart from tetrahedral geometry, another possible geometry for CH₄ is square planar with the four H atoms at the corners of the square and the C atom at its centre. Explain why CH₄ is not square planar?

The skeletal structure of CH₃COOH as shown below is correct, but some of the bonds are shown incorrectly. Write the correct Lewis structure for acetic acid.

Arrange the bonds in order of increasing ionic character in the molecules: LiF, K₂O, N₂, SO₂ and ClF₃.

Explain with the help of suitable example polar covalent bond.

Define electronegativity. How does it differ from electron gain enthalpy?

Write the expression for the equilibrium constant, K_c for each of the following reactions: 

1. \(2NOCl (g) ⇋ 2NO (g) + Cl_2 (g)\)
2. \(2Cu(NO_3)_2 (s) ⇋ 2CuO (s) + 4NO_2 (g) + O_2 (g)\)
3. \(CH_3COOC_2H_5(aq) + H_2O(l) ⇋ CH_3COOH (aq) + C_2H_5OH (aq)\)
4. \(Fe^{3+} (aq) + 3OH^– (aq) ⇋ Fe(OH)_3 (s)\)
5. \(I_2 (s) + 5F_2 ⇋ 2IF_5\)

Write the significance/applications of dipole moment.

Find out the value of \(K_c\) for each of the following equilibria from the value of \(K_p\): 

1. \(2NOCl (g) ⇋ 2NO (g) + Cl_2 (g); \ K_p= 1.8 × 10^{–2}\  at \ 500\ K\)
2. \(CaCO_3 (s) ⇋ CaO(s) + CO_2(g); \ K_p= 167 \ at \ 1073\  K\)

Use Lewis symbols to show electron transfer between the following atoms to form cations and anions:

1. K and S 
2. Ca and O 
3. Al and N.

Write the resonance structures for SO₃ , NO₂ and NO₃^-

Explain the important aspects of resonance with reference to the \(CO_3^{2-}\) ion.

Although geometries of NH₃ and H₂O molecules are distorted tetrahedral, bond angle in water is less than that of ammonia. Discuss.

Discuss the shape of the following molecules using the VSEPR model: 
BeCl₂, BCl₃, SiCl₄, AsF₅, H₂S, PH₃

Define octet rule. Write its significance and limitations.

Considering the elements F, Cl, O and N, the correct order of their chemical reactivity in terms of oxidizing property is:

At a certain temperature and total pressure of 10⁵ Pa, iodine vapour contains 40% by volume of \(\text {I}\) atoms
\( I_2 (g) ⇋ 2I (g)\)
Calculate K_p for the equilibrium.

Considering the elements B, C, N, F, and Si, the correct order of their non-metallic character is:

Considering the elements B, Al, Mg, and K, the correct order of their metallic character is:

Which of the following statements related to the modern periodic table is incorrect?

What is K_c for the following equilibrium when the equilibrium concentration of each substance is: [SO₂]= 0.60 M, [O₂] = 0.82 M and [SO₃] = 1.90 M ?
\(2SO_2(g) + O_2(g) ⇋ 2SO_3(g)\)