In a reversible reaction, the forward reaction takes place {after, before, simultaneously} the reverse reaction. such a reaction, on reaching equilibrium, will have

In a reversible reaction, the forward reaction takes place simultaneously the reverse reaction. Such a reaction, on reaching equilibrium, will have equal rate of going forward and going backward.

Explanation: It is a reaction in which the reactants reacts to give products and products reacts to give the reactants back simultaneously.

In the above reaction reactants A and B reacts together to give products C and D, and vice versa.

In these reaction rate of reaction going forward is equal the rate of reaction going backward at the equilibrium.

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

58750.08068 is the answer i think