Balanced equation: 2Fe + 3H2O → Fe2O3 +3H2
Convert g to mols:
285/55.845 = 5.1034 mols
Mole ratio of Iron and Iron (III) Oxide: 2:1
5.1034/2 = 2.5517 mols
 
        
             
        
        
        
Flash drivers are more robust, if you drop it, it is still most likely to work. Hard drivers provide more storage. There’s not much difference
        
             
        
        
        
Zeff = Z - S
Here, Z is the number of protons in the nucleus, that is, atomic number, and S is the number of nonvalence electrons. 
For boron, the electronic configuration is 1s₂ 2s₂ 2p₄
Z = 5, S = 2 
Zeff = 5-2 = +3
For O, electronic configuration is 1s₂ 2s₂ 2p₄
Z = 8, S = 2
Zeff = 8-2 = +6
Hence, the correct answer is second option, that is, +3 and +6, the Zeff of boron is smaller in comparison to O, thus, boron exhibits a bigger size than O. 
 
        
             
        
        
        
You always adjust numbers and it will be before the element 
so you Neva add or change a subscript
        
                    
             
        
        
        
In the reaction,
Cr3+(aq) + 6H2O -------> [Cr(H2O)6]3+(aq)
Cr3+ IS THE LEWIS ACID H2O is the Lewis base. 
A Lewis acid is a compound or chemical that accepts a lone pair of electrons. In the above equation, Cr3+ is accepting the lone pair of electrons.