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Assertion : Potassium and caesium are useful as electrodes in photoelectric cells.
Reason : Potassium and caesium, when irradiated with light, the light energy absorbed is sufficient to eject out the electron from an atom.
(A). Low ionisation energies of potassium and caesium.
Assertion : The alkaline earth metals have much higher melting and boiling points than those of the alkali metals.
Reason : The melting and boiling points of alkaline earth metal do not vary in a regular fashion.
(B). Atom/ions of alkaline earth metals are smaller than the corresponding alkali metals. These atoms/ions are packed more closely in their lattices. Alkaline earth metals have two valence electrons and alkali metals have only one. Larger number of valence electrons leads to stronger interatomic interactions in alkaline earth metals. As a result, therefore, the melting and boiling points of alkaline earth metals are higher than those of alkali metals.
Assertion : The ionisation enthalpies of alkaline earth metals are fairly low.
Reason : In general, the low ionisation enthalpies of alkaline earth metals are due to large size of their atoms.
(A). Alkali metals have only one valence electron, while alkaline earth metals have two valence electrons. After the only outermost electron is removed from the atom of an alkali metal, the ion formed has a stable configuration of the nearest noble gas. Removal of another electron from the unipositive ion of alkali metal, therefore, would require very large amount of energy.
Both Be and Al become passive on reaction with concentrated nitric acid due to:
Both Be and Al are rendered passive due to formation of inert, insoluble and impervious oxide layer on their surface.
Which loses weight on exposure to the atmosphere ?
(c) CO2 escapes out slowly.
Which of the following compound is weakest Lewis acid ?
Extent of back bonding decreases from BF3 to BI3. So, lewis acidic character increases from BF3 to BI3. Hence, BF3 is the weakest lewis acid.
Which does not show inert pair effect
Al does not show inert pair effect due to unavailability of d subshell.
Pick the correct statement :
Mark the oxide which is amphoteric in character
CO2 - acidic,
CO - neutral,
SnO2 - amphoteric,
CaO - basic
In B2H6
In B2H6, there is no direct boron-boron bond. The structure is not similar to that of C2H6 (ethane). The boron atoms are linked through hydrogen bridges, forming a bridged structure. The atoms are not in one plane. Therefore, the correct option is o3: the boron atoms are linked through hydrogen bridges.
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