Conjunction -ki  in the end 

When conjunction -ki comes in the very end of a question sentence, it expresses"worry,anxiety or  curiosity "

-Bizimle yemek yer mi ki ? ---> I wonder if he/she would have meal with us ?

- [Yakında Türkiye´ye yerleşeceğim.] 6 ayda Türkçe öğrenebilir miyim ki ? ---> [I am bit worried ]if I can learn Turkish in 6 months.

- Oraya gidince eski arkadaşlarımı görür müyüm ki ? --> I am curious if I could see my old friends when I go there ?

- Hatice hanımlar gelir mi ki ?  ---> I wonder if Mrs. Hatice would come ?

- Bana kızar mı ki ? --->[ I am worried ]I wonder if he/she would get angry with me ?

teşekkür ederiz.

ki at the end and acaba arasındaki ne fark eder ki?

Lütfen

-ki is a conjunction and "acaba" is a noun. But in this specific case, acaba and ki function smilarly. 

for example ;

1. Acaba bana kızar mı ?

2. Bana kızar mı ki ?

In both sentence, you are wondering if that person would get angry with you.

However,in my opinion, the second sentence [with ki] conveys a slight worry. Worry of the possibility of that person´s getting angry with you whereas the first sentence conveys more "curiosity".