I teach Higher Level chemistry and I didn't have any IB experience when I started at my current school. The school will be interested in how much A level you have taught and importantly how good your subject knowledge is. The IB chemistry syllabus is less broad than the A level I also teach but it is taught in much more depth. There are some pretty complicated topics that you may not have studied since university. The coursework is very different too as they have to come up with their own research question and come up with their own set of variables that they are going to investigate. You should expect to be given training, the Ibicus course I went on was great. If you teach chemistry, you can pm me.