# Hydrides of group 5 and 6

1. Aug 17, 2009

### leena19

Hello everyone,
this is a question I've asked at another chemistry forum,
and has been bothering me for awhile .
http://www.chemicalforums.com/index.php?topic=34742.0"

And ... the only only reason I'm posting it here aswell,is causeI have my chem exam on Thursday(the day after tomorrow) and...I'm the kinda idiot(also a blabbermouth) who can't skip a problem unless I'm absolutely sure I've understood it,so... I would really appreciate it if I could find a solution to this before my exams...

And oh...I know I ask alot of stupid questions ,so if you think this is one of those,just tell me & i won't bother you guys.
(well,i might pester your'll with other questions,but no more pestering after my exams,for atleast a week,promise. :) )

thx.

Last edited by a moderator: Apr 24, 2017
2. Aug 18, 2009

### chemisttree

You say that the acidity of the hydrides increases from top to bottom (from NH3 to AsH3) and that the reverse is seen if you go backwards from BiH3 to SbH3! Wouldn't the reverse also be seen if you go from AsH3 to NH3?

Sounds like someone is asking you a trick question....

3. Aug 18, 2009

### leena19

THANK YOU VERY MUCH FOR REPLYING!

Er...is that a trick question ?
Sorry if my problem isn't clear,but this is basically what my question is,

$$\stackrel{\leftarrow}{}$$
Arranged in increasing order of acid strength
AsH3 > PH3 > NH3 > SbH3 > BiH3

The acidity increases from NH3 to AsH3,then the acidic strength decreases from SbH3 to BiH3 .
What makes the group5 hydrides react this way?

4. Aug 18, 2009

### chemisttree

What is the oxidation state of Bi in the BiH3 compound? What about BiH2-?

Acidity reaction would be:

BiH3 <--------> BiH2- + H+

5. Aug 18, 2009

### leena19

All group 5 hydrides are trivalent,so the oxidation state of Bi would be -3

The same. -3 ?

Not sure how to proceed from here.

6. Aug 18, 2009

### chemisttree

Last edited by a moderator: Apr 24, 2017
7. Aug 18, 2009

### leena19

Thanks for the very useful link.
Ok so the oxidation state of Bi in BiH3 is +3 and in BiH2-,it is +1 .
Then,since it's a metal it has to be more basic(i.e less acidic) than SbH3.
But SbH3 and AsH3 are metalloids...?

Can you tell me what I should do next?

thx.

Last edited: Aug 18, 2009