0.000 988 M KMnO4 21.08 mL 10.0 mL Ca^2+ mg

0.000 988 M KMnO4 21.08 mL 10.0 mL Ca^2+ mg

 

 

Calcium levels in blood can be determined

by adding oxalate ion to precipitate calcium oxalate, CaC2O4,

followed by dissolving the precipitate in aqueous acid

and titrating the resulting oxalic acid (H2C2O4) with KMnO4:

5H2C2O4(aq) + 2MnO4^-(aq) + 6H^+(aq)

→ 10CO2(g) + 2Mn^2+(aq) + 8H2O(l)

 

How many milligrams of Ca^2+ are present in 10.0 mL of blood

if 21.08 mL of 0.000 988 M KMnO4 solution is needed for the titration?

 

 

 

0.000988 M KMnO4 21.08 mL에 들어있는

KMnO4의 몰수

= (0.000988 mol/L) (21.08/1000 L)

= 2.0827×10^(-5) mol KMnO4

( 참고 https://ywpop.tistory.com/7787 )

 

 

 

5H2C2O4(aq) + 2MnO4^-(aq) + 6H^+(aq)

→ 10CO2(g) + 2Mn^2+(aq) + 8H2O(l)

 

H2C2O4 : MnO4^- = 5 : 2 = ? mol : 2.0827×10^(-5) mol

 

? = 5 × (2.0827×10^(-5)) / 2

= 5.20675×10^(-5) mol H2C2O4

= 5.20675×10^(-5) mol C2O4^2-

= 5.20675×10^(-5) mol Ca^2+

 

 

 

Ca의 몰질량 = 40.08 g/mol 이므로,

(5.20675×10^(-5) mol) × (40.08 g/mol)

= 0.002087 g Ca^2+

= 2.087 mg Ca^2+

 

 

 

답: 2.09 mg

 

 

 

 

[참고] 혈중 칼슘 농도(ppm)를 계산해보면,

2.087 mg / (10.0/1000 L)

= 208.7 mg/L

= 208.7 ppm

 

 

 

 

[키워드] 혈중 칼슘 농도 기준