Two positively charged objects are located so they are 0.20 m apart. if the objects are separated until their centres are 0.40 m apart, by what factor will the electrostatic force between them change?

In a particular chemical reaction, the energy of the reactants is 30 kj and the energy of the products is 5 kj. 
 the maximum energy of the system is 40 kj. sketch a potential energy diagram for this reaction. make sure to label the energy of the reactants, the energy of the products, the activation energy, and the enthalpy change for the reaction.