If you are sent an invitation or Facebook request to try "Watsapp On PC", please do not. This is a scam and has nothing to do with "WhatsApp". Cyber-criminals created this scam with the fake name "Watsapp On PC", to send spam to your Facebook friends, by sending them invitations to itself and taking them to on-line advertisement and survey websites.
The Fake Facebook WhatsApp Invitation - Watsapp On PC

What the scammers have done is to create a fake Facebook application called ‘Watsapp On PC’.
Note: the legitimate name is ‘WhatsApp’ and not ‘Watsapp’
The legitimate WhatsApp Facebook page is located at the following address:
www.facebook.com/whatsapp.official
Always go to the legitimate WhatsApp Facebook page and verify any WhatsApp information, application or service before granting access to your account, sharing, liking, commenting on any Facebook post, which claims that they are associated with WhatsApp.
If you click on the invitation, you will be asked to grant or give this fake application access to your Facebook application.
Once you have given it access, it will then ask you to send the request to all of your Facebook friends, in order for you to use the service. But, this is a trick used by the scammers who have created this fake application, to send it to other Facebook users.
This fake WhatsApp application is located on the malicious website:
www.galaxybilliardsjaipur.com
If you are taken to this website, please do not follow the instructions on it and close the web browser window.
Now, if you were tricked into installing this fake WhatsApp application, please click the link below for instructions on how to remove a Facebook application, and remove all Facebook applications with the name: Watsapp On PC.
Click here for instruction on how to remove the fake WhatsApp application.
Also, if you have received an invitation try this bogus service (Watsapp On PC), please report it to Facebook and then delete it.
This fake Facebook application is located on Facebook at the following address (remove spaces in URL):
https://apps.facebook.com /1497495977137074/ ?fb_source=notification &request_ids=447622655372033
This scam is related to the following: