How is the reaction quotient used to determine whether a system is at equilibrium? a at equilibrium, the reaction quotient is undefined. b the reaction is at equilibrium when q> keq. c the reaction is at equilibrium when q=keq. d the reaction is at equilibrium when q

The correct answer is C the reaction is at equilibrium when q = Keq
1-As when q > Keq :
the reaction is not at equilibrium, the reaction will move towards the left to increase the reactants and decrease the products to achieve equilibrium, and the reaction is preferring the reverse reaction to achieve the equilibrium.

2- and when q< Keq:
the reaction is not at equilibrium, the reaction will move towards the right to increase the products and decrease the reactants to achieve equilibrium, and the reaction is preferring the forward reaction to achieve the equilibrium.

3-and when q= Keq
This means that the reaction is at equilibrium, and there is no shift to right or to the left to make equilibrium, and the forward and reverse reaction is at the same rate. 
So the correct answer is C the reaction is at equilibrium when q = Keq

The ratio is 3: 2. i.e. c.

Vander waals forces are inter molecular bonds that exist within molecules of the same substance. a water molecule is made up of oxygen and hydrogen atoms which share electrons between each other. the vander waals forces are forces that exist between multitude of different  molecules of water. dipole dipole forces is the type of vander waals force that exist in water. the oxygen atom which is more electronegative pulls the shared electron closer to itself thus generating a partial negative charge while the hydrogen acquire a partial positive charge. these two different charges causes attraction to occur in water molecules.