H2O or water, all humans are mostly mad of water and water covers most of the earth 
        
             
        
        
        
Answer:
6
Explanation:
Formula: Al2O3
 If we require 2Al2O3
                        We divide 2 by 3
Sorry for the shadow of phone and fingers.
  
 
        
             
        
        
        
No, because humans are much more complex than peas.
        
                    
             
        
        
        
Answer:
6.4 × 10^-10 M
Explanation:
The molar solubility of the ions in a compound can be calculated from the Ksp (solubility constant). 
CaF2 will dissociate as follows:
CaF2 ⇌Ca2+ + 2F- 
 1 mole of Calcium ion (x)
2 moles of fluorine ion (2x)
NaF will also dissociate as follows:
NaF ⇌ Na+ + F-
Where Na+ = 0.25M
F- = 0.25M
The total concentration of fluoride ion in the solution is (2x + 0.25M), however, due to common ion effect i.e. 2x<0.25, 2x can be neglected. This means that concentration of fluoride ion will be 0.25M
Ksp = {Ca2+}{F-}^2
Ksp = {x}{0.25}^2
4.0 × 10^-11 = 0.25^2 × x
4.0 × 10^-11 = 0.0625x
x = 4.0 × 10^-11 ÷ 6.25 × 10^-2
x = 4/6.25 × 10^ (-11+2)
x = 0.64 × 10^-9
x = 6.4 × 10^-10
Therefore, the molar solubility of CaF2 in NaF solution is 6.4 × 10^-10M