Bi 4. NH LNG ACID SALICYLIC TRONG THUC M BNG PHNG PHP QUANG PH HP TH PHN T

I. C s l thuyt II. Chun b1. Ha cht- Dung dch FeCl3 0,1% g/ml.- Dung dch acid salicylic 0,05% g/ml. - Thuc m bi da Betasalic (10g) cha acid salicylic 300 mg (SV chun b - mua cng s l).2. Dng c- My quang ph UV-VIS.- Cc bnh nh mc 25ml (9 ci).- Cc pipet chnh xc.- Cc c m.- Cc thy tinh. - ng so mu, giy lc- Bp cch thy/ bp in.III. Qui trnh thc hnh1. Chun b dy dung dch - Cn chnh xc khong 0,1700 g thuc m, cho vo cc c m nh, thm nc ct, un nng cho thnh cht lng sau ngui. Lc qua giy lc v nh mc 25 ml bng nc ct. Lc u thu c dung dch mu th X.- Pha cc dung dch theo bng sau:Bnh 10mlMTA1A2A3A4A5X1X2

Dd acid salicylic 0,05% g/ml (ml)0,20,51,01,52,0

Dung dch X (ml)3,03,0

Dd FeCl3 0,1% g/ml trong HCl (ml)1515151515151515

Nc ct va (ml)2525252525252525

A

2. Phng php so mu bng mtLy dung dch X1 so snh cng mu ca cc dung dch t A1 n A5. T suy ra c nng ca dung dch acid salicylic cn nh lng.3. Phng php so snh chuno mt quang DX ca dung dch X1 bc sng 527 nm. o mt quang ca dung dch c cng mu xp x nh dung dch X1 (trong dy dung dch t A1 n A5) c DCh. Ta tnh cng CX ca dung dch X1 :Cx = Dx.Cch/DchTnh hm lng acid salicylic trong thuc m.3. Phng php ng chunLp ng chun o mt quang D1, D2, D3, D4, D5 ca 5 dung dch t A1 n A5. V th s ph thuc ca D v nng acid salicylic chun.o mt quang Dy ca dung dch X2 bc sng 527 nm, da vo ng chun v, suy ra nng Cy ca acid salicylic trong dung dch X2.Tnh hm lng acid salicylic trong thuc m.IV. Cu hi lng gi1. Trnh by c s l thuyt ca phng php.2. Trnh by nhng hn ch (nhng nguyn nhn gy sai s) ca phng php.3. Nhn xt cc th tch ly pha cc dung dch trong bng, v sao?