True or False type question chemistry - Periodic Properties

1. Dispositive zinc exhibits paramagnetism due to loss of two electrons from 3d-orbital of neutral atom. (JEE 1987)

False.

Reason: Zn²⁺ exhibits diamagnetism. Formation of the ion involves loss of two electrons from 4s orbital. The resultant configuration of 10 electrons in 3d orbital does not have unpaired electrons. So it exhibits diamagnetism.

2. In Group IA of alkali metals, the ionization potential decreases down the group. Therefore lithium is a poor reducing agent.

False

Reducing strength is determined by the negative of reduction potential (i.e., oxidation potential) and not by the ionization potential. Lithium is the strongest reducing agent among alkali metals.

3. Both potassium ferrocyanide and potassium ferricyanide are diamagnetic. (JEE 1989)

False

Potassium ferrocyanide is diamagnetic (no unpaired electron) while potassium ferricyanide is paramagnetic (one unpaired electron)

4. The presence of polar bonds in a polyatomic molecule suggests that the molecule has non-zero dipole moment. (JEE 1990)

False

There are polyatomic molecules with polar bonds that have zero dipole moment due to symmetric arrangement of polar bonds.

5. The decreasing order of electron affinity of F,Cl, Br is F>Cl>Br. (JEE 1993)

False

The order is Cl>F>Br. Due to the small size in F atom there is larger electronic repulsion. Hence electron affinity is more in Cl than in F.


6. The basic nature of hydroxides of Group13 (Gr. III B) decreases progressively down the group. (JEE 1993)

False

Basic nature increases as the element becomes more metallic. As one goes down the group metallic character increases.

Chemistry - Ture or False Type Questions in Atomic Structure

1. The outer electronic configuration of the ground state chromium atom is 3d⁴4s². (JEE 1982)

False

Chromium atomic number is 24.
Its our electronic configuration is 3d⁵4s² .

2. The energy of the electron in the 3d-orbital is less than that in the 4s-orbital in the hydrogen atom. (JEE 1983)
Ans: True.

Chemistry - Ture or False Type Questions in Inorganic chemistry

State whether the following statements are true or false
1. Red phosphorus is less volatile than white phosphorus because the former has a tetrahedral structure. (1982)

2. MgCl2.6H2O on heating gives anhydrous MgCl2. (1982)

3. When PbO2 reacts with a dilute acid, it gives hydrogen peroxide. (1982)

4. Copper metal reduces Fe²⁺ in an acid medium. (1982)

5. Silver fluoride is fairly soluble in water. (1982)

6. Dilute HCl oxidizes metallic Fe to Fe²⁺. (1983)

7. In an aqueous solution chlorine is a stronger oxidizing agent than fluorine. (1984)

8. Silver chloride is more soluble in very concentrated sodium chloride solution than in pure water. (1984)

9. Solubility of sodium hydroxide increases with increase in temperature. (1985)

10. Sodium when burnt in excess of oxygen gives sodium oxide. (1987).

11. Both potassium ferrocyanide and potassium ferricyanide are diamagnetic. (1989)

12. Cu⁺ disproportionates to Cu²⁺. (1991)

13. Nitrous oxide, though an odd electron molecule, is diamagnetic in liquid state. (1991)

14. Diamond is harder than graphite. (1993)

15. The basic nature of the hydroxides of Group 13 (Gr. III B) decreases progressively down the group. (1993)

16. The tendency for catenation is much higher for C than for Si. (1993)

17. HBr is stronger acid than HI because of hydrogen bonding. (1993)

IIT JEE Chemistry Old questions with answer

State True or False

1. If equilibrium constant for the reaction A2 + B2 ↔ 2AB, is K, then for the backward reaction AB ↔ ½ A2 + ½ B2, the equilibrium constant is 1/K.

(JEE 1984)

Answer: False

Reason: For A2 + B2 ↔ 2AB,
K = [AB] ²/[A2][B2]

For AB ↔ ½ A2 + ½ B2 equilibrium constant is

= [A2] 1/2[B2] 1/2/[AB]

This is not equal to 1/K.

2. Solubility of sodium hydroxide increases with increase in temperature.
(JEE 1985).

Answer: False

The dissolution of NaOH in water is an exothermic process. According to Le Chatelier principle, solubility decreases with increase in temperature. Increase in temperature favours backward reaction.



3. The rate of exothermic reaction increases with increasing temperature.
(JEE 1990).

Answer: True
Reason: In general, rate of a reaction increases with increase in temperature which is due to increase in the rate constant of the reaction. As per the Arrhenius equation relating k and T, as temperature increases k increases. (Note: At equilibrium if the temperature is increased, for an exothermic reaction the equilibrium shifts leftward).

Fill in blanks

4. For a given reversible reaction, at a fixed temperature equilibrium constants Kp and Kc are related by ____________________ .
(JEE 1994)

Answer : Kp = Kc (RT) Δ vg



5. A ten fold increase in pressure on the reaction


N2(g) + 3H2(g) ↔ 2NH3(g) at equilibrium results in _____________ in Kp.


(JEE 1996)

Answer: no change

Reason: Kp of an equilibrium reaction is independent of pressure of the system.

6. For a gaseous reaction 2B → A, the equilibrium constant Kp is _____________ to/than Kc.
(JEE 1997)

Answer: smaller

MCQs with multiple answers

7. When NaNO3 is heated in a closed vessel, oxygen is liberated and NaNO2 is left behind. At equilibrium

a. addition of NaNO2 favours reverse reaction.
b. addition of NaNO3 favours forward reaction.
c. increasing temperature favours forward reaction.
d. increasing temperature favours reverse reaction.

(1986)

Answer: ( c), (d),

Reason:

2NaNO3(s) ↔ 2NaNO2(s) + O2 (g)

Kp = Pressure of O2

Changing the quantities of NaNO3 and NaNO3 does not affect equilibrium position as Kp or Pressure of O2 remains constant.

Increasing temperature favours the forward reaction as this is endothermic direction.
Increasing pressure shifts the reaction in the backward direction as Pressure of O2 has to be kept constant.

8. For the reaction


PCl5 (g) ↔ PCl3 (g) + Cl2 (g)


The forward reaction at constant temperature is favoured by

a. introducing an inert gas at constant volume.
b. introducing chlorine gas at constant volume.
c. introducing an inert gas at constant pressure.
d. introducing PCl5 at constant volume.
e. increasing volume of the container
(1991)

Answer: c, d, and e.

Reason: Introducing an inert gas at constant pressure would increase the volume of the system. So the equilibrium shifts towards the side with larger number of gaseous molecules, i.e. the reaction proceeds in the forward direction.

Increasing volume produces the same result.

Introducing PCl5 at constant volume increases the concentration of the reactant and thus equilibrium is shifted in the forward direction.