In alkali metal group which is the strongest reducing agent and why?

Q: In alkali metal group which is the strongest reducing agent and why?

Sol: Li is the strongest reducing agent. Since I.P. decreases down the group we would expect that Li will have the lowest reducing power in that group. But since it’s hydration energy is very high and which in fact decreases down the group, Li will have highest reducing power.

(ii)Although Aluminium is above hydrogen in the electrochemical series, it is stable in air and water. Explain.

Sol: (ii) Due to the formation of protective oxide layer on its surface.

Among fluorine – fluorine bond and chlorine – chlorine bond, which is more stronger and why?

Q: Among fluorine – fluorine bond and chlorine – chlorine bond, which is more stronger and why?

Sol: In Cl—Cl bond, a filled p-orbital of chlorine can overlap with a suitable vacant d-orbital of adjacent chlorine thereby introducing some double bond character. Thus the bond strength increases. This is not possible in fluorine as it has got no vacant d-orbital.

NaOH behaves as a base while Zn(OH)2 is amphoteric why ?

Q: NaOH behaves as a base while Zn(OH)2 is amphoteric why ?

Sol: In NaOH the bond electronegativity difference between Na and oxygen is greater than between H and O and therefore it is the Na–O bond that breaks releasing OH. But in case of Zn—O—H bond the difference of electronegativity of Zn—O and O—H are almost same. So there is equal probability that the bond breaks in both ways leading to an amphoteric behaviour

Electron affinity of SF5 is among the highest known but that of SF6 is quite modest.Why?

Q: Electron affinity of SF5 is among the highest known but that of SF6 is quite modest.Why?

Solution: Sulfur in SF6 is saturated in terms of maximum covalency and maximum co-ordination number and so it has very little tendency to attract electron. In SF5 which is actually a free radical so it has got a very strong tendency to attract an electron to fulfill its covalency and co-ordination number. There fore the electron affinity of SF5 is high.

The ionisation energy of the coinage metals fall in the order Cu > Ag > Au.Why?

Q: The ionisation energy of the coinage metals fall in the order Cu > Ag > Au.Why?

Solution: In all the 3 cases an s-electron in the unpaired state is to be removed. In the case of Cu a 4s electron is to be removed which is closer to the nucleus than the 5s electron of Ag. So I.P. decreases from Cu to Ag. However from Ag to Au the 14 f electrons are added which provide very poor shielding effect. The nuclear charge is thus enhanced and therefore the outer electron of Au is more tightly held and so the IP is high.

The first I.P. of nitrogen is greater than oxygen while the reverse is true for their second I.P. values.why?

Q: The first I.P. of nitrogen is greater than oxygen while the reverse is true for their second I.P. values.why?

Solution: The first I.P corresponds to the removal of first electron. Since nitrogen is already half filled. So more energy is required to remove the electron. But once the electron is removed from oxygen it gains half filled stability and therefore the 2nd I.P. becomes high.

Berilium and Al are placed in different periods and groups but they show the similar properties.Why ?

Q: Berilium and Al are placed in different periods and groups but they show the similar properties.Why ?

Solution: On moving across a period the charge on the ions increases and the size decreases, causing the polarising power to increase. On moving down a group the size increases and polarising power decreases. On moving diagonally i.e., from Be to Al these two effects partly cancel each other and so there is no marked change in properties.