The atomic numbers of elements X,Y and Z are 19, 21 and 25 respectively. The number of electrons present in the M-shell of these elements follow the order

• Z > X > Y

• X > Y > Z

• Z > Y > X

• Y > Z > X

An electron is moving in Bohr's fourth orbit. Its de-Broglie wave length is λ. What is the circumference of the fourth orbit ?

• 2/λ

• 2λ

• 4λ

• 4/λ

Which of the following is a linear molecule?

• BeCl₂

• H₂O

• SO₂

• CH₄

Which of the following is correct?

• The number of electrons present in the valence shell of S in SF₆ is 12.

• The rates of ionic reactions are very slow

• According to VSEPR theory, SnCl₂ is a linear molecule.

• The correct order of ability to form ionic compounds among Na⁺, Mg²⁺ and Al³⁺ is  Al³⁺ >Mg²⁺ >Na⁺.

x grams of calcium carbonate was completely burnt in air. The weight of the solid residue formed is 28 g. What is the value of x (in grams)?

• 44

• 200

• 150

• 50

A and B are ideal gases. The molecular weights of A and B are in the ratio of 1 :4. The pressure of a gas mixture containing equal weights of A and B is P atm. What is the partial pressure (in atm) of B in the mixture?

• P/5

• P/2

• P/2.5

• 3P/4

Assertion (A): The pH of a buffer solution containing equal moles of acetic acid and sodium acetate is 4.8 (pK_a of acetic acid is 4.8).

Reason (R): The ionic product of water at 25°C is 10^-14mol².L^-2. The correct answer is

• Both (A) and (R) are true and (R) is the correct explanation of (A)

• Both (A) and (R) are true and (R) is not the correct explanation of (A)

• (A) is true but (R) is not true

• (A) is not true but (R) is true

At 550 K, the K_c for the following reaction is 10⁴ mol^-1L $\mathrm{X}\left(\mathrm{g}\right) + \mathrm{Y} \left(\mathrm{g}\right) \rightleftharpoons \mathrm{Z}\left(\mathrm{g}\right)$. At equilibrium, it was observed that $\left[\mathrm{X}\right] =\frac{1}{2}\left[\mathrm{Y}\right] =\frac{1}{2}\left[\mathrm{Z}\right]$. What is the value of [Z] (in mol L^-1) at equilibrium?

• 2 × 10^-4

• 10^-4

• 2 × 10⁴

• 10⁴

Which of the following is not correct?

• Dissolution of NH₄Cl in excess of water is an endothermic process.

• Neutralisation process is always exothermic

• The absolute value of enthalpy (H) can be determined experimentally.

• The heat of reaction at constant volume is denoted by ΔE.

The pH of a solution of H₂O₂ is 6.0. Some chlorine gas is bubbled into this solution. Which of the following is correct?

• The pH of resultant solution becomes 8.0

• Hydrogen gas is liberated from resultant solution

• The pH of resultant solunon becomes less than 6.0 and oxygen gas is liberated

• Cl₂O is formed in the resultant solution