Predict the relative pH (acidic, basic, or neutral) of a 1.0 M solution of the f
ID: 891567 • Letter: P
Question
Predict the relative pH (acidic, basic, or neutral) of a 1.0 M solution of the following salts. (acidic = pH less than 7; neutral = pH approximately 7; basic = pH greater than 7) (2 pts each)
sodium formate (formic acid Ka = 1.8 × 10-4) _________________________
ammonium formate (ammonia Kb = 1.8 × 10-5) _________________________
sodium hydrogen sulfate (Ka1 = very large; _________________________
Ka2 = 1.2 × 10-2)
potassium hypochlorite (HOCl Ka = 3.5 × 10-8) _________________________
disodium phosphate (H3PO4Ka1 = 7.5 × 10-2; _________________________
a2 = 6.2 × 10-8; Ka3 = 4.8 × 10-13)
Explanation / Answer
1)
sodium formate (formic acid Ka = 1.8 × 10-4)
sodium formate HCOONa this is salt of weak acid and strong base. so the pH is greater than 7, basic
2)
ammonium formate (ammonia Kb = 1.8 × 10-5)
it is the salt of weak acid + weak base .pH can be decided by Ka of acid and Kb of base .
formic acid Ka = Ka = 1.8 × 10-4
NH3 Kb = Ka = 1.8 × 10-5
Ka > Kb . so acid dominate .
pH < 7 and it is acidic
3)
sodium hydrogen sulfate
sodium hydrogen sulfate NaHSO4 . this is a salt of strong acid and strong base. so the pH = approximately 7. neutral
(4)
potassium hypochlorite (HOCl Ka = 3.5 × 10-8)
KOCl is satl of strong base + weak acid . so pH > 7 it is basic
(5)
Na2HPO4 it is still having one acidic proton . so it is acid .
pH < 7 and acidic