Can we generate Sales from Facebook Advertising, if yes what would be the expected conversion rate from Facebook?

Depends on which region you're talking about, but from personal experience FB is extremely effective.

How good your social media content is usually defines your conversion rate.

Utilizing Facebook's advertising platform does indeed generate sales. Your conversion rate is all dependent upon how well you advertise, how often you refresh the advertisement in the minds of the Facebook community, and how specific you are about your target market and outreach. It is very important to manage your geographic market and ensure that you are reaching the proper age group, cultural group, and general demographic. A good number to aim for in regards to conversion is 20% conversion rate. So if you're targeting 10,000 customers, you should be looking to convert about 2,000 of those individuals into customers. Through proper advertising and the use of relevant images, colors, and language, you will attract the customers you are targeting.

Thanks for the invitation, to answer the question posted first of all you need to let us know the type of business you are into, then only would be in a position to suggest whether Facebook will work in your favor or not.

One size cant fit to all at the end :) 

Using Facebook is one of the social media  advertisement. 

It is help you to target your customers by country /city,  by age, gender and by interests.  So you could generate sales from it. The ads cost depends on the country and the period it starts from 5$