heat of formation and solubility confusion =(

[sony102]

1)which of the following substances does not have a heat of formation equal to zero at standard conditions?
a)F2(g)
b)Cl2(g)
c)Br2(g)
d)I2(g)

I am stuck between C and D , I know that in standard conditions Bromine is Liquid and Iodine is solid not gas so both C and D should have a non zero heat of formation, but only one answer is correct, how can you eliminate one aswer ??

2)which is the weakest electrolyte?
a) NH4I
b)LiF
c) AgBr
d)H2O2

the correct ansr is D but it also says in the explanation "All ionic compounds, whether soluble or not, are defined as strong electrolytes so choices A,B,C are eliminated.
it's this explanation that confuses me AgBr is insoluble, how can it be a strong electrolye?? electrolyts must produce ions in aquous solution and conduct electricity, without being soluble you can't produce ions or conduct electricity, why do they still call insoluble ionic compounds strong electrolytes???
I am sure that AgBr is insoluble, according to the solubility rules in my text book

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[minhaj]

I am clueless on number 1. maybe entropy has something do with it.

As for number 2, even though AgBr is not very soluble, some of the molecules will dissociate. In case of H2O2, there is no way that any ions can be generated from from that molecule. Hence, it is the weakest electrolyte.

 

[sony102]

thanks
#1 is a question from MCAT princeton review hyperlink , how did you guys get past this question if you studied princetonn?? is it a mistake??