Elements that are in the same columns (vertical) are chemically similar. 
Carbon- Si
Cesium- Na
Krypton- Ar 
Magnesium- Ca
Al- try Boron
Br try Cl
These are just the ones I picked but it could be any in the same column
        
             
        
        
        
The array will be created with the elements equal to null.
        
             
        
        
        
Answer:
Synthesis - 4
reversible- 2
exchange- 1
decomposition-3
Explanation:
In synthesis reaction two or more components combines to form a single product. example 2H2+O2⇒2H2O
In reversible reaction two reactants combine to form two products . The products then reacts and forms back the reactants. example N2 +3H2 ⇒2NH3
In exchange reaction there is an alternation of ions of reactants to form new products. AB+CD ⇒AC + BD 
In decomposition reaction, molecules of a compound break down by the action of heat or light or catalyst. example CaCO3 ⇒CaO +CO2
 
        
             
        
        
        
Answer:
The answer to your question is 1.1 moles of water
Explanation:
                      2Al(OH)₃  +   3H₂SO₄   ⇒   Al₂(SO₄)₃  +   6H₂O
                        0.45 mol      0.55 mol                                ?
Process
1.- Calculate the limiting reactant
Theoretical proportion
        Al(OH)₃ / H₂SO₄ = 2/3 = 0.667
Experimental proportion
        Al(OH)₃ / H₂SO₄ = 0.45 / 0.55 = 0.81
From the proportions, we conclude that the limiting reactant is H₂SO₄
2.- Calculate the moles of H₂O
                         3 moles of H₂SO₄ ----------------  6 moles of water
                         0.55 moles of H₂SO₄ -----------    x
                         x = (0.55 x 6) / 3
                         x = 3.3 / 3
                         x = 1.1 moles of water