If I were you I would choose CS + ECE since you will get both world of the information technology: the software and the hardware. Learning about the logic gates, CPU design and computer architecture in general in your ECE classes will make you appreciate the intricacy of computer programming that you learn in your CS classes. They really complement each other. I know this for sure since I did take a CPU design class where the final project was to design a custom MIPS CPU that understands a custom Assembly language, and it was fun and mind-breaking
OTOH, I would not go the CS + ChemE path since I always have this impression that computer and chemical don't mix. I would end up having to do mental switchings when attending and doing homework between CS and ChemE classes. But this is just my opinion anyway so in the end you need to ask yourself which do you prefer.