Would you use a toothbrush with nylon bristles if nylon were soluble in water

The identities of substances are the same before and after which type of change

In a heat engine of 1000 j of heat enters the system and the piston does 500 j of work what is the final internal energy of the system if the inital energy was 2000 j we have to do all of these down here 1)write the equation 2)list out your know variables 3)plug the numbers into the equations 4)solve 5)write your solution statemtn that includes inital energuy and final energuy added

What is the oxidation state of each individual carbon atom in c2o42−?