Give reasons for the following ,
a. `Dil HCl ` is preferred as compared to dil `H_2 SO_4 ` for the preparation fo ` CO-4` while `SnO` is soluble .
b. CO_2 does not support combustion but a burning magnesium ribbon conitnues to burn in it .
c, `PbO` does not dissolve in `H_2 SO_4` , while `SnO` is soluvble
d. `NaOH` cannot be stored in Sn of pb vessel .
e. Alkances are more stable than silances .

Explanation

a. Marble, `CaCO_(3)`, reacts with dil `H_(2)SO_(4)`, to form white ppt. of `CaSO_(4)`, which gets deposited on the surface of the marble and acts as a protective layer. Thus, further reaction between marble and dil `H_(2)SO_(4)` is prevented.
`CaCO_(3)+ underset(dil)(H_(2)SO_(4))rarr underset("White ppt.")(CaSO_(4)darr)+CO_(2)uarr+H_(2)O`
However, dil `HCl` reacts with marble to form `CaCl_(2)` which does not get deposited on the marble surface and thus rection between `CaqCO_(3)` and dil `HCl` resulting in the liberation of `CO_(2)` continues.
`CaCO_(3) +2HClrarr caCl_(2) +CO_(2) uarr +H_(2)O`
b. `CO_(2)` does not support combustion but burning magensium ribblon continues to burn in it, as Mg reduces `CO_(2)` to `C` and therefore Mg continues to burn in it. ltbRgt `CO_(2)+2Mgrarr C+MgO`
`PnO` reacts with `H_(2)SO_(4)` to form `PbSO_(4)` which is insoluble in water and hence `PbO` does not dissolve in `H_(2)SO_(4)`.
`PbO+H_(2)SO_(4) rarrunderset(("white ppt."))underset("Lead sulphate")(PbSO_(4)darr)+ H_(2)O`
However, `SnO` on reaction with `H_(2)SO_(4)` form `SnSO_(4)`,
which is soluble, hence, `SnO` dissolves in `H_(2) SO_(4)`.
`SNO+H_(2)SO_(4) rarr SnSO_(4) +H_(2)O`
d. `NaOH` cannot be stored in Sn or Pb vessel as Sn and `Pb` dissolve in `NaOH` due to the formation of sodium stannate and sodium plumbate respectively, both of which are soluble.
Sn=2HaOH+H_(2)O rarr underset(("soluble"))underset("Sodium stannate")(Na_(2)SnO_(2)+) 2H_(2)`
Pb+2NaOH rarrunderset(("soluble"))underset("Sodium plumbare")(Na2PbO_(2)+)2H_(2)`
e. Alkanes are more stable than silanes because `C-C` bonds in alkanes are more stable than `Si-Si` bonds in silanes due to greater extent of overlap between the `2sp^(3) -2sp^(3)` hyvbridised orbitals of `C` as compared to `3 sp^(3) -0 3 sp^(3)` hybridised orbitals of `Si.