I've been working for a few months now in my new work and originally I signed to be an iOS Developer. During the interview however I stated that I can do web development so that is something that I need to do from time to time as it is my employers services is to provide Facebook apps for their client. When I came in, the company was outsourcing the Android app and website of our biggest project to another country while I take over the iOS version of the app. After a month my employer got impressed with me and decided to stop outsourcing and asked me to take over the Android app. I declined for the reason that I wanted to make sure I can focus on the iOS app and not under deliver because I am not that good with Android development. But my employer insisted and so I had to say yes. After a few months I started to take over another project this time a web site.
My question is, would it be reasonable to ask for a salary raise after my probation? If I for example earn $100 for being an iOS dev. Would it be reasonable to ask for $50 more if I do web development and Android development? The point is I am now doing new responsibilities on top of being an iOS developer.