Preposition + Noun/Noun + Preposition

There is one prepositional phrase with the wrong preposition in each group of nouns below. Cross it out. 

1.  at the same time, at all cost, at first sight, at favour of, at the request of 
2.  in other words, in disorder, in my opinion, in average, in a whisper, in general
3. on the phone,  on the other hand, on the bus, on addition to, on the Internet
4. out of date, out of purpose, out of order, out of cash, out of time  
5. on duty, on business, on arrival, on the news, on the screen, on a diet, on fire 
6. by chance, by far, by mistake, by heart, by sight, by purpose  
7. without need, without doubt, without breath, without exception, without delay