I have previously read that the boiling point of Stibane(SbH3) is greater than Ammonia(NH3) together ammonia is gas at room temperature and also no hydrogen bonding exist in the gaseous type of NH3.Hence, as SbH3 is higher in size, has higher molecular weight; its boil pint is higher than NH3.why walk Stibane have actually a higher boiling point than Ammonia

In the case, of AsH3, also this molecule is gas at room temperature and its boiling allude should be better than NH3, yet this is not the case and NH3 has actually a higher boiling allude than AsH3.

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I want to know what is the reason behind this trend. (NH3 having a higher boiling point than AsH3)


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asked january 21 in ~ 3:58
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Aaliya AhamedAaliya Ahamed
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There is the basic trend in the teams 15, 16, 17 of raising of boiling points for the binary compounds with hydrogen, going down the groups.

But the very first members the each group - $ceNH3, H2O, HF$ - have actually anomally v their cook points being exceptionally high, early hydrogen bonds. The toughness of this bonds and also the boiling allude decreases in the order $ceH2O > HF > NH3$.

See the figure 2 on wordpress page for an illustrative picture:

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Hydrogen bonds play function in (not restricted to):

evaporation and also boiling, together molecules need to get an extra power to get over these bonds and also to to escape liquid.condensation, acting together cohesive pressure for molecule to stick come each various other or to a condensation center.gas pressure, together the inter-molecular cohesive pressure decreases the gas pressure, compared to the push of perfect gas in ~ the very same conditions.

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Note the the fact that both NH3 and AsH3 space gases at room temperature is irregularity for the above.

Not having in hand method for quantitative analysis, so just thoughts:

$ceNH3$ has actually the the very least polar bonds and their dipole moments in big extent mutually cancel each various other due sterical orientation.$ceHF$ is the many polar v the greatest electronegativity difference, yet this seems about beaten through 2 polar bonds of $ceH2O$, both having very similar dipole moments. What may play function is much better sterical availability ( 2 versus 1 ) that water hydrogen for shared hydrogen bonding.