For each of the following salts, write its chemical name and indicate whether a
ID: 941318 • Letter: F
Question
For each of the following salts, write its chemical name and indicate whether a 1.00 M aqueous solution is acidic, basic or neutral at 300 K. Clearly explain your choices. Appendix D on page 1103– 1104 may be useful. I'm just stuck on comparing the Ka and Kb values for C and D. Not sure where to go with that.
(a) NaClO (c) (NH4)2SO4
(b) Na2S (d) (NH4)(CHO2)
CH,COOH (or HC·11,01 1.0 × 10 3.0× 10-12 1.6 × 10-12 CH COOH or HC H,02 C,H,cooH (or HCH,02) 5.6 x 0 HooCC(on)(CH,COOH) (or H,C,H,O,) 1.7 × 10-5 4.0 × 10-7 Hydrogen peroxide 1 × 10-19 CH CHIOH)COOH (or HC,H,0,) CH[COOH) HC,H-04 2.0 x 10 6.4 x 10 C,H,OH (or HCH:O) C,H COOH r HC,H02 4.2 × 10-13 Pyrophosphoric acid 2.1 x 10 6.4 x 10-Explanation / Answer
(a) NaClO ------------------> sodium hypochlorite
it is basic . it is salt of weak acid and strong base. so basic property is dominent
NaOH + HClO ------------------------> NaOCl + H2O
strong base weak acid basic salt
(b) Na2S -----------------> sodium sulfide
it is also basic slat of weak acid (H2S) and strong base (NaOH) . so base properties are dominent
(c) (NH4)2SO4 -----------------> ammonium sulfate . it is acidic
it is the salt of weak base NH4OH and strong acid H2SO4 . so acidic properties are dominent
(d) (NH4)(CHO2) --------------------> ammonium formate .
it is the salt of weak acid and weak base. the nature of the salt decided by pK values of acid and base
NH4OH , pKb = - log Kb = -log (1.8 x 10^-5) = 4.74
HCO2 H , pKa = -log Ka = -log (1.8 x10^-4) = 3.74
pKa < pKb . so acidic properties are dominent . so it is slightly acidic salt . the pH will be 6.95
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