Assertion (A) : Graphite is slippery and used as a lubricant.
Reason (R) : Graphite has free electrons.
Graphite possesses a layer structure with two successive layers held by weak force and able to slide over one another.
So, graphite is slippery and this property finds its use as a lubricant.
In graphite, each carbon atom is linked to three other carbon atoms while one electron in the carbon atom is delocalised.
So, graphite has free electrons.