They are the basic components of life or the basic building blocks of life
        
                    
             
        
        
        
In the electrolytic cell, depending on the polarity of the battery, either a more vigorous reaction (though the same as the voltaic cell) would occur, or the reverse would.
        
             
        
        
        
1. The reaction for this would be:
Sn + 4 HNO₃ →  SnO₂ + 4 NO₂ + 2 H₂O
The first observation would be bubbling of the solution and brown acrid smoke is produced due to the presence of NO₂ gas. Another observation would be the presence of a white solid which is SnO₂.
2. Heating was required to get rid of the H₂O. When all moisture is gone, you weigh the sample. Afterwhich, you further heat it to get ride of the oxygen. By doing this, you would know the individual mass of each element. Then, you can solve for the empirical formula of the oxide of tin.
        
             
        
        
        
4Al(s) + 3O2(g) --> 2Al2O3(s)    This is the balanced.
From the equation:
 4 moles of Al required 3 moles of O2 to produce 2 moles of Al2O3
 
3 moles of O2 reacted with 4 moles of Al to produce 2 moles of Al2O3
1 mole of O2 reacted with 4/3 moles of Al to produce 2/3 moles of Al2O3  (Divide by 3)
4.5 moles of O2 reacted with (4/3 *4.5) moles of Al to produce (2/3*4.5) moles of Al2O3
4.5 moles of O2 reacted with 6moles of Al to produce  3moles of Al2O3
(3) is the answer.  6 mol of Al.