Question

TWO MARKS QUESTIONS

1. PbX2 is more stable than PbX4 . Explain

2. Galium has higher ionization enthalpy than Aluminium. Why?

3. Why is BF3 weaker lewis acid than BCl3?

4. What happens when boric acid is heated?

5. Why are lithium halides are covalent in nature?



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Answer 1

1 ANSWER :-

• Due to inert pair effect +2 oxidation state of Pb is more stable than its +4 oxidation state. Consequently PbX2 in which the oxidation state of Pb is +2 is more stable than PbX4 in which the oxidation state of Pb is +4.

2 ANSWER:-

• ➪effective nuclear charge will increase and hence Ga will be smaller in size than Al. As nuclear charge is more, it is difficult to remove an electron from outermost shell of Ga, hence ionization energy is more than Al.

3 ANSWER:

• ➪In contrast, toward weak bases such as CO, BF3 is a stronger Lewis acid than BCl3. ... It takes more energy to lengthen the short strong BF bonds than the longer weaker BCl bonds and it is for this reason that BCl3 is a stronger Lewis acid than BF3 toward a strong base such as NH3.

4 ANSWER:-

• ➪When boric acid is heated it converts to metabolic acid which on further heating gives boron trioxide. Answer: On strong heating, first the Boric acid (H3BO3) breaks up into Metaboric acid (HBO2) and Water (H2O). On further heating, the Metaboric acid breaks up into Boric oxide (B2O3) and Water.

5 ANSWER:-

• ➪The salts of alkali metals are the most ionic salts known. Although lithium is an alkali metal yet its compounds., particularly halides, are slightly covalent in nature. This is because the Li* ion has small size and has maximum tendency to withdraw the electrons towards itself from the negative ion.

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Answer 2

1.) Due to inert pair effect +2 oxidation state of Pb is more stable than its +4 oxidation state. Consequently PbX2 in which the oxidation state of Pb is +2 is more stable than PbX4 in which the oxidation state of Pb is +4.

HOPE IT WILL HELP YOU.