residue

As nouns the difference between residue and coke

is that residue is whatever remains after something else has been removed while coke is (uncountable) solid residue from roasting coal in a coke oven; used principally as a fuel and in the production of steel and formerly as a domestic fuel or coke can be (informal|slang|uncountable) cocaine or coke can be (informal|countable) any cola-flavored drink, especially coca-cola.

As a verb coke is

to produce coke from coal.

In context|chemistry|lang=en terms the difference between residue and ash

is that residue is (chemistry) the substance that remains after evaporation, distillation, filtration or any similar process while ash is (chemistry) to reduce to a residue of ash see ashing .

As nouns the difference between residue and ash

is that residue is whatever remains after something else has been removed while ash is the solid remains of a fire or ash can be (countable|uncountable) a shade tree of the genus fraxinus .

As a verb ash is

(chemistry) to reduce to a residue of ash see ashing .