If done with dedication, chemical engineering is a very tough branch which requires a lot of hard work and dedication. However, if you're a slacker like I am, nothing will ever seem easy or difficult. it is all just a phase.
You should have a good working knowledge of calculus, especially differential equations. Furthermore, there are several concepts of physics you should be familiar with such as thermodynamics to be able to grasp chemical engineering at its depth.
As mentioned before, if you are a slacker and don't plan on doing chemical engineering with dedication, don't worry. All you have to do is memorize everything two days before the exam just like any other branch of engineering.