The reaction A $$ \to $$ B follows first order kinetics. The time taken for 0.8 mole of A to produce 0.6 mole of B is 1 hour. What is the time taken for conversion of 0.9 mole of A to produce 0.675 mole of B?

The activation energy for a simple chemical reaction A $$\rightleftharpoons$$ B is E_$$a$$ in forward direction.
The activation energy for reverse reaction

2A $$ \to $$ B + C

It would be a zero order reaction when

For the reaction;

2N₂O₅ $$ \to $$ 4NO₂ + O₂ rate and rate constant are 1.02 $$ \times $$ 10^$$-$$4 and 3.4 $$ \times $$ 10^$$-$$5 sec^$$-$$1 respectively, then concentration of N₂O₅ at that time will be