What does this question mean
        
                    
             
        
        
        
Answer:
- <em>(B.) The pH of a buffer solution is determined by the ratio of the concentration of conjugate base to the concentration of strong acid.</em>
- <em>(C.) A buffer is generally made up of a weak acid and its conjugate base. </em>
- <em>(D.) The pH of a buffer solution does not change significantly when any amount of a strong acid is added.</em>
Explanation:
A buffer is  solution which resists change in pH upon addition of either acids or bases.
The pH of a buffer is calculated by the ratio of the concentration  of base to concentration of acid. The weak acid and conjugate base have a Ka similar to the pH desired.
 
        
             
        
        
        
Explanation:
According to the analysis, Molarity is amount mole per volume(1L). the amount in mole would be molarity × volume in litres. 
0.500M × (250/1000)L= 0.125moles.
I hope this helps**
 
        
             
        
        
        
 <span>D. all of the above because ionic compound is a salt. it is also held together by ionic bonds. it has anions and cations </span>