hello Sr,

Hope you are doing well ,Now to answer your question

As we know that Molar mass of ammonia is 17g

17g ammonia contains 6.022×10^23 number of ammonia molecules due to this 4.25 g ammonia will contain,

(6.022×10^23×4.25)/17 = 1.5×10^23

number of ammonia molecules.

hope this will help you a lot

thank you.

Dear Aspirant

No. Of moles =gmwt weight=4.25÷17

=.25

No of moles ×NA=no. of molecules

No. Of molecules = .25×6.023×10^23

= 1.5×1023

I hope it will help you

Thank you