I highly doubt that this would work properly. Since both operating systems use the same binary format (ELF), it should "theoretically" be possible. But in reality they are sharing only a small subset of APIs (POSIX).
A linux executable gets the path of the dynamic linker into the header section (usually something like /lib/ld-linux.so). This is also an executable. The operating system kernel reads this while creating the new process, then loads and executes this other executable binary. In an chroot environment with openbsd there is no such linker, because bsd has it's own linker.
Also bsd has a different system call and library call interface than linux. So linux doen't know bsd syscalls. Interestingly bsd has a compatibility for linux binaries, but not inverse.
Conclusion: If you just want to "try" openbsd, why don't you try a live USB-stick of openbsd?