Question

1The phosphorous atom in phosphate groups has a partial positive charge due to the fact that:

Select one:

a. Phosphate groups have trigonal planar geometry

b. Phosphorous is bound to highly electronegative oxygen atoms

c. phosphate groups are highly soluble in water

d. Phosphorous groups have several resonance forms (NOT THIS ONE)

e. All of the above

Consider the following phosphate transfer reaction that is exergonic under standard conditions:

A~P + B → B~P + A  

2The standard free energy for A~P → A + Pi is -25.6 kj/mol

What can be predicted for the standard free energy of: B + Pi --> B~P ?

Select one:

a. -25.6 kj/mol

b. -12.0 kj/mol

c. +12.0 kj/mol

d. +25.6 kj/mol **NOT THIS ONE

e. None of the above

Answer 1

1. If Phosphorous is supposed to be in tetrahedral geometry then it has to form covalent bonds(As the symmetry of tetrahedral arrangement is sp³ hybridization. It can do so in the present of electropositive atoms easily.

But in this case due to the presence of high electronegativity Oxygen atoms, the bonds get polarised and the electron cloud is more towards the oxygen atom.

2. For the second reaction, we need to have Keq values or the concentration of moieties involved to use in

delta G = delta Go + RT ln[Products]/[Reactants]

Anyways the reaction is supposed to be exothermic and it cant be equal to the give free energy. Hence the predicted value of standard free energy will be -12.0 kJ/mol.