Seems you got some things mixed up...
When you install Fedora using the default disc layout, it will create LVM partitions on your hard disc. Those are in what is called a volume group. When you issued the mount command with /dev/VolGroup... you are basically telling it to mount your already mounted partitions again.
To find out what your optical drive is called, type in on the console:
It will answer you with
eject: device is `...'
The device that is shown between the quotes, let's assume it's /dev/hdc, use that in your mount command
mount /dev/hdc /mnt/hdc
You may want to remember, that the /dev folder is for devices, not for mounts.
Quite often, more then one link to the optical drive is provided, like /dev/cdrom or /dev/dvd and so on, those are usually symlinks to the actual device name, which in the above case is /dev/hdc