List of top Chemistry Questions

In terms of period and group where would you locate the element with Z =114?

Write the atomic number of the element present in the third period and seventeenth group of the periodic table.

Which element do you think would have been named by
(i) Lawrence Berkeley Laboratory
(ii) Seaborg's group?

Why do elements in the same group have similar physical and chemical properties?

What does atomic radius and ionic radius really mean to you?

How does atomic radius vary in a period and in a group? How do you explain the variation?

What do you understand by isoelectronic species? Name a species that will be isoelectronic with each of the following atoms or ions. 

1. F^- 
2. Ar 
3. Mg²⁺ 
4. Rb⁺

Consider the following species: N^3- , O^2-, F^-, Na⁺, Mg²⁺ and Al³⁺ 

1. What is common in them? 
2. Arrange them in the order of increasing ionic radii.

Explain why cations are smaller and anions larger in radii than their parent atoms?

Anything that influences the valence electrons will affect the chemistry of the element. Which one of the following factors does not affect the valence shell?

What are the various factors due to which the ionization enthalpy of the main group elements tends to decrease down a group?

The first ionization enthalpy values (in kJmol^-1 ) of group 13 elements are :

B	Al	Ga	In	Tl
801	577	579	558	589

How would you explain this deviation from the general trend?

Which of the following pairs of elements would have a more negative electron gain enthalpy? 

1. O or F 
2. F or Cl

Dinitrogen and dihydrogen react with each other to produce ammonia according to the following chemical equation: \(N_2 (g) + H_2 (g) → 2NH_3 (g)\)

1. Calculate the mass of ammonia produced if 2.00 × 10³ g dinitrogen reacts with 1.00 × 10³ g of dihydrogen.
2. Will any of the two reactants remain unreacted?
3. If yes, which one and what would be its mass?

How are 0.50 mol Na₂CO₃ and 0.50 M Na₂CO₃ different?

If 10 volumes of dihydrogen gas reacts with five volumes of dioxygen gas, how many volumes of water vapour would be produced?

(i) Calculate the number of electrons which will together weigh one gram.
(ii) Calculate the mass and charge of one mole of electrons.

Convert the following into basic units:

1. 28.7 pm
2. 15.15 pm
3. 25365 mg

How would you explain the fact that the first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium?

Among the second period elements the actual ionization enthalpies are in the order 
Li < B < Be < C < O < N < F < Ne. 
Explain why 

1. Be has higher Δ_iH than B
2. O has lower Δ_iH than N and F?

Energy of an electron in the ground state of the hydrogen atom is -2.18 x 10^-18  J. Calculate the ionization enthalpy of atomic hydrogen in terms of J mol^-1  .

In a reaction \(A + B_2 → AB_2\) Identify the limiting reagent, if any, in the following reaction mixtures.

1. 300 atoms of A + 200 molecules of B
2. 2 mol A + 3 mol B
3. 100 atoms of A + 100 molecules of B
4. 5 mol A + 2.5 mol B
5. 2.5 mol A + 5 mol B

If the speed of light is 3.0×10⁸ ms^–1, calculate the distance covered by light in 2.00 ns.

What is the significance of the terms - 'isolated gaseous atom' and 'ground state' while defining the ionization enthalpy and electron gain enthalpy?
Hint: Requirements for comparison purposes.