Question

The combination of gaseous atoms of non-metal X and of hydrogen atom to form gaseous X2H6 molecules.

2X(g) + 6H (g). ----> X2H6 (g)
The bond energy of an X-H is 395kJ/mil.
What's the bond energy of X-X?

Answer 1

did they have mentioned any other data please check once again

Answer 2

you have to tell me the delta H for the following reaction it is missing in the question

Answer 3

really some value is missing in this :)

Answer 4

Oh, yes! I missed that. That's -2775KJ/mol

Answer 5

ok ok

Answer 6

in this X2 H6
you have 6 X-H bonds and 1 X-X bond right

Answer 7

Yeah I know that already

Answer 8

energy liberated bcoz of both 6-X-H bond +1 X-X bond is -2775 KJ

but if u calculate for the 6-X-H bonds it is =6*395 = 2370 KJ
therefore remaining willbe liberated when X-X bonds are formed =2775-2370 = 405 KJ

Answer 9

did u get it :)

Answer 10

Sign changing? How?

Answer 11

whenever bonds are formed energy will be released hence- ve sign :)

Answer 12

6 X-H + X-X = -2775 KJ
-2370 + X-X = -2775 KJ
X-X =-2775+2370 = -405 KJ

Answer 13

bond energy is positive (+) or may be negative(-)
if bonds are formed u use -ve sign bcoz energy is liberated in this phenomenon
if bonds has to be broken out then use a +ve sign bcoz energy is needed to break it

Answer 14

I got it now. Thank you so much. :)