1.203 g H3AsO4 0.05871 M AgNO3 40.00 mL Ag3AsO4

1.203 g H3AsO4 0.05871 M AgNO3 40.00 mL Ag3AsO4

 

 

농약 시료 1.203 g 중에 존재하는 비소는

적절한 처리에 의해 H3AsO4로 변환되었다.

이 산을 중화시킨 후

0.05871 M AgNO3 용액 40.00 mL를 첨가하여

정량적으로 Ag3AsO4를 침전시켰다.

 

 

The arsenic in a 1.203 g sample of a pesticide

was converted to H3AsO4 by suitable treatment.

The acid was then neutralized,

and 40.00 mL of 0.05871 M AgNO3 was added

to precipitate the arsenic quantitatively as Ag3AsO4.

The excess Ag^+ in the filtrate and in the washings from the precipitate

was titrated with 9.63 mL of 0.1000 M KSCN,

and the reaction was Ag^+ + SCN^- → AgSCN(s)

Find the percentage of As2O3 in the sample.

 

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첨가한(added) Ag^+의 몰수

= (0.05871 mmol/mL) (40.00 mL) = 2.348 mmol Ag^+

 

 

 

여분의(excess) Ag^+의 몰수

= (0.1000 mmol/mL) (9.63 mL) = 0.963 mmol Ag^+

 

 

 

Ag3AsO4 침전에 소비된 Ag^+의 몰수

= 2.348 – 0.963 = 1.385 mmol Ag^+

 

 

 

Ag3AsO4에서 Ag : As = 3 : 1 개수비(= 몰수비) 이고,

As2O3에서 As2O3 : As = 1 : 2 개수비(= 몰수비) 이고,

As2O3의 몰질량 = 197.84 g/mol 이므로,

 

(1.385 mmol Ag^+) (1 As / 3 Ag) (1 As2O3 / 2 As) (197.84 mg As2O3 / 1 mmol As2O3)

= (1.385) (1 / 3) (1 / 2) (197.84)

= 45.67 mg Ag2O3

= 0.04567 g Ag2O3

 

 

 

As2O3의 퍼센트를 계산하면,

(0.04567 g / 1.203 g) × 100

= 3.796%

 

 

 

답: 3.796% Ag2O3