It shouldn't hurt it, it will still burn. Many Semis usually put used motor oil in their gas tanks just to get rid of it as SOP in their motorpools.
I've never seen one with a weedeater, but I have seen one with an edger. That would be nice wouldn't it? How about the Packer-combo-mower ?
Nothing would happen.
nothing
The surplus will drop back onto the lawn.
I barely know.
it will explode
Your clothes would get cleaner.
it would make the fire get bigger
There will be no human
It depends on the design of the mower. In one it might blow the fuse, in another it might go backwards. Or the blade might go backwards, which would be useless.
Same thing as mixing ammonia and bleach. You'll get chlorine gas, which was used in WWI for anti-trench warfare.
The salt would dissolve, which you can reverse by boiling the water.