When dealing with making diluted solutions from concentrated solutions, we can use the following formula 
c1v1 = c2v2 
where c1 and v1 are the concentration and volume of the concentrated solution respectively.
c2 and v2 are the concentration and volume of the diluted solution respectively 
substituting these values in the above formula,
20 mL x 0.200 M = C x 250.0 mL 
C = 0.0160 M 
        
             
        
        
        
A covalent compound is formed when a chemical reaction occurs between atoms of separate molecules
        
                    
             
        
        
        
There are different kinds of reactions. To name some, these are the synthesis reaction, decomposition reaction, single-replacement reaction, double-replacement reaction, combustion reaction, redox reaction, etc. For this type of reaction involving two reactants to yield only one product, <em>this is a synthesis reaction.</em>
<em>P₄ (s) + 6 Ca (s) --> 2 Ca₃P₂ (s)</em>