Answer:
Colourless
Explanation:
We know that Y^3+ has the electronic configuration of;
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 (the 5s and 4d levels are empty).
According to the crystal field theory, the colour of complexes result from transitions between incompletely filled d orbitals.
As a result of this, complexes with empty or completely filled d orbitals are colourless. Thus,  [Y(H2O)6]3 is colourless according to the Crystal Field Theory.
 
        
             
        
        
        
Answer:
Benzoic acid is the stronger acid
Explanation:
Weak acids do not dissociate completely in the solution. They exists in equilibrium with their respective ions in the solution. 
The extent of dissociation of the acid furnising hydrogen ions can be determined by using dissociation constant of acid ( ).
).
Thus for a weak acid, HA

The  is:
 is:
![K_a= \frac{[A^-][H^+]}{[HA]}](https://tex.z-dn.net/?f=K_a%3D%20%5Cfrac%7B%5BA%5E-%5D%5BH%5E%2B%5D%7D%7B%5BHA%5D%7D)
The more the  , the more the acid dissociates, the more the stronger is the acid.
, the more the acid dissociates, the more the stronger is the acid.
Also, 
 is defined as the negative logarithm of
 is defined as the negative logarithm of  .
.
So, more the  , less is the
, less is the  and vice versa
 and vice versa
All can be summed up as:
The less the value of  , the more the
, the more the   is and the more the acid dissociates and the more the stronger is the acid.
 is and the more the acid dissociates and the more the stronger is the acid.
Given, 
 of acetic acid = 54.7
 of acetic acid = 54.7
 of benzoic acid = 54.2
 of benzoic acid = 54.2
 of benzoic acid <
 of benzoic acid <  of acetic acid
 of acetic acid
So, benzoic acid is the stronger acid.