Question

Identify the species represented by each curve in the fractional composition diagram of a diprotic acid (H,A) with pK, values of 5.00 and 9.00 НА HA A2- Fractional composition 1.00 0.90 0.80 0.70 0.60 0.50 0.40- 0.30- 0.20 0.102 Answer Bank a 0 10 11 12 13 pH Calculate the fraction of the diprotic acid in each of its forms at pH 5.27. CHA

Answer 1

Identify the species represented by each curve in the fractional composition diagram of a diprotic acid (HA) with pK, values of 5.00 and 9.00 NA IIN Fractional composition 1.00- 0.90 0.80- 0.70 0.60 0.50 0.40 0:30 0.20 0.10 Answer Bank НА НА 0 9 10 11 12 13 Calculate the fraction of the diprotic acid in each of its forms at pH 5.25. NA-0.360 44 = 0.640 0.000114

0.00011 Part (a): cca bmit For a diprotic acid, dissociation follocos step process which is as tha HT+HAT (kan) HÃ Ht + A2- (Kaz) Thus, for step 1, the equilibrium equation is given as, Kas [HTJLNA [HA -log Lont ICA] MA] (taking negative log => -- log Kas = -log[nt] - logging 2A] > p Kas = pH- log [HA] ... (1) [A] Thus, when the have 47 s. e. the Curve of chat and [16A] Similarly, for stepa, we will have okaz = gpl - log (A2-] are intercetting (2) > Log Kas Thus, when pH = pkay = 9.0, we have ha ] = A2] lie. 2 LUA- and A2- intersecting The curve are SHOT ON REDMI Y3 AIDUAL CAMERA

of Part (6) or Thus we see that the curve SA- intersects twice, once the curve of thA at pH = 5.00 and then the curve of A2- at pt 29.00 Hence, this is the central curve (deep blue colour). The curve of tha intersects that I HA- at pH= 5.00. Thus, it is reeds colored curve. the third core is blue sky be) in Here, we will assume that (A2-] = a, [HA] = b and HAJ-C pH = 5.2 C one son altain from Equation (1) , we user płag =pl - lop na [2 A = 5:00 = 5.27 - lg 3 (putting 100.27 nabees) 1.862 0.5376. SHOT ON REDMI Y3 AI DUAL CAMERA

from equation, we have op Kaz=pH - LA2 ha 0.5376 » X H₂A = 1.862x10 46+6+0.5376 from (3) and (4) =>XH₂A ~ 0.359 ) NA ~0.36 for ha => 9:00= 5:27 - log q (putting the values, Asia - foto >> Grip = 1862 > a = 10-12 6 6 1.862x10 " 6+6+ 0.5376 from (3) and (4) 2) LHA - 90 638) KNA-~0.64 Hadise 202 (9 1.862 810-4b The fraction , & can be written as Kha= arbre For A2- a atbtc SHOT ON REDMI Y3 AI DUAL CAMERA

UDDI 1.862 810-4 b 1.862 810-4b+b+0.5376 s) LAZ ~ 0.0ool1398 => XA2-70.000114 The final auswer is in the attached do drawing DDDDD)))) SHOT ON REDMI Y3 AIDUAL CAMERA