Why is a sign never given with the value of activation evergy

 It is aklways assume to be a positive number:  energy must be added to initiate the reaction, but will be sustained by the heat of it's own reaction.

Explanation:  I never thought about this, but my answer would be that, by it's nature, activiation energy is always supplied to the system, so it is assume to be positive, unlike enthaly, which is either added (endothermic, positive) or released (exothermic, negative) from the system.  A negative activation energy makes no sense - it only tells us the reaction may be spontaneous.

state the principle of separating two immiscible liquids by separating funnel. describe an activity with diagram to separate a mixture of water and kerosene oil. answer: immiscible layers separate out in layers depending on their densities in separating funne