Question

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Make separate (50ml) of .05M chromium (III) nitrate and a 0.20M Cobalt (II) nitrate in distilled water.

After making the stock solution make five standards in which the absorbance falls from 0.1 A.U to 1AU

Answer 1

a) To prepare 0.5M chromium (III) nitrate in distilled water.

moecular weight of Cr(NO₃)₃ : 238.11 gm/ mole

To prepare 1 M Cr(NO₃)₃ solution disolve 238.11 gm Cr(NO₃)₃ solid in distilled water and dilute it upto 1 lit.

if we want to prepare a 0.5M Cr(NO₃)₃ solution then disolve 119.05 gm Cr(NO₃)₃ solid in distilled water and dilute it upto 1 lit.

Simillarly for 50 ml solution we can calculate as,

weight of solid = 50 ml x 119.05/ 1000 = 5.9525gm solid to be disolve in distill water and dilute to 50ml it will be 0.5M Solution.

b) To prepare 0.20M Cobalt (II) nitrate in distilled water.

moecular weight of Co(NO₃)₂ : 182.94 gm/ mole

To prepare 1 M Co(NO₃)₂ solution disolve 182.94 gm Co(NO₃)₂ solid in distilled water and dilute it upto 1 lit.

if we want to prepare a 0.2M Co(NO₃)₂ solution then disolve 36.588 gm Co(NO₃)₂ solid in distilled water and dilute it upto 1 lit.

For 50 ml solution we can calculate as ,

weight of solid = 50 ml x 36.588/ 1000 = 1.82gm solid to be disolve in distill water and dilute to 50ml it will be 0.2M Solution.

Once you prepare these stack solutions then check the absorbence for each solution based on the absorbence you can easily calculate the concentration Vs absorbence relation and prepare (Dilute) a standard solutions with distill water to get 1 AU to 0.1 AU absorbence.