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11.31     Write balanced equations for:

$(iv)\; H_{3}BO_{3}\overset{\Delta }{\rightarrow}$

Orthoboric acid on heating gives metaboric acid with the removal of 4 molecules of water and on further heating, metaboric acid converts to tetraboric acid and later on Boron trioxide (boric anhydride)

7.40    List the uses of neon and argon gases.

We use Neon in discharge tubes and fluorescent bulbs for advertisement display purposes. Neon bulbs are used in botanical gardens and in green houses. We use Argon mainly to provide an inert atmosphere during metallurgical processes involving high temperature(arc welding of metals or alloys) and for filling electric bulbs. We use It  in the laboratory too  for handling substances that are air-sensitive

7.39     Why do noble gases have comparatively large atomic sizes?

The atomic radius of an element corresponds to the covalent radius. but noble gases do not form any molecule, so for them, the radius is Vander walls radius. Vander wall radius is larger than the covalent radius.

7.38   Give the formula and describe the structure of a noble gas species which is isostructural with:

$BrO_{3}^{-}$

XeO3 has a pyramidal molecular structure and is isostructural to BrO-3 and.

7.38     Give the formula and describe the structure of a noble gas species which is isostructural with:

$IBr_{2}^{-}$

XeF2 has a linear structure and is isoelectronic to  IBr-2 and

7.38     Give the formula and describe the structure of a noble gas species which is isostructural with:

$ICI_{4}^{-}$

XeF4  has square planar geometry and is isoelectronic with  ICl-4 .

7.37    Which one of the following does not exist?

$(i)\:XeOF_{4}$

$(ii)\:NeF_{2}$

$(iii)\:XeF_{2}$

$(iv)\:XeF_{6}$

does not exist because neon has very high ionization enthalpy. But ionization enthalpy of xenon is low.

7.36     Arrange the following in the order of property indicated for each set:

(iii)  $NH_{3}$, $PH_{3}$,$AsH_{3}$ , $SbH_{3}$$BiH_{3}$  – increasing base strength.

As we move from nitrogen to bismuth, the size of the atom increases and the electron density on the atom decreases. hence, the basic strength will decrease.

7.36     Arrange the following in the order of property indicated for each set:

(ii)  $HF$, $HCl$, $HBr$$HI$ - increasing acid strength.

The dissociation energy of bond of  H-X molecules where X = F, Cl, Br, I, decreases as we increase the atomic size. HI is the strongest acid Since H-I bond is the weakest

7.36     Arrange the following in the order of property indicated for each set:

(i)     $F_{2}$, $CI_{2}$, $Br_{2}$, $I_{2}$- increasing bond dissociation enthalpy.

Bond dissociation energy usually decreases as we move down in a group, Bond dissociation energy usually decreases as the atomic size increases. whereas, the bond dissociation energy of  is lower than that of and . This is due to the small atomic size of fluorine. hence,

7.35     How are $XeO_{3}$ and $XeOF_{4}$  prepared?

When we do Hydrolysis of and with water we get                                                                       And  Partial hydrolysis of gives us,

7.34     With what neutral molecule is $ClO^{-}$ isoelectronic? Is that molecule a Lewis base?

Total electrons in   is isoelectronic with two neutral molecules. And these two are and In In both species also contain 26 electrons.

7.33     How are xenon fluorides $XeF_{2}$$XeF_{4}$  and $XeF_{6}$  obtained?

Under different concentration of Xenon, it forms , XeF2 , XeF4 and XeF6 by the direct reaction. XeF6 can also be made by the interacting and at 143K.

7.32     Write balanced equations for the following:

(ii) Chlorine gas is passed into a solution of $NaI$ in water.

Chlorine gas is passed into a solution of water

7.32     Write balanced equations for the following:

(i)  $NaCl$  is heated with sulphuric acid in the presence of  $MnO_{2}$.

Nacl is heated with sulphuric acid in presence of Kmno4

7.31     What are the oxidation states of phosphorus in the following:

$POF_{3}$

It is known that the oxidation state of the oxygen and fluorine are -2 and -1 respectively Let oxidation state be x  So, the oxidation state of the phosphorus in  is +5

7.31     What are the oxidation states of phosphorus in the following:

$Na_{3}PO_{4}$

we know the oxidation state of sodium() is +1 and oxygen() is -2 Let Oxidation state = x Thus the oxidation state of phosphorus in  is +5

7.31     What are the oxidation states of phosphorus in the following:

$Ca_{3}P_{2}$

We know that the oxidation state of  calcium is +2 let oxidation state  be  Hence the oxidation state of the phosphorus is -3

7.31    What are the oxidation states of phosphorus in the following:

$PCl_{3}$

It is known that the oxidation state of chlorine is -1 let oxidation state  be  hence oxidation state phosphorus in   is +3

7.31     What are the oxidation states of phosphorus in the following:

$H_{3}PO_{_{3}}$

It is known that the oxidation state of H = 1 and O is -2. Let the oxidation state of  be x hence oxidation state of  is  3
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