Go on the internet and find the MSDS (Material Safety Data Sheet) for hydrogen s

Question

Go on the internet and find the MSDS (Material Safety Data Sheet) for hydrogen sulfide H_2 S Print it out and attach to your prelab. Are there any safety issues related to H_2 S? You are given an unknown solution that contains only one of the Group II cations and no other metallic cations. Develop the simplest procedure you can think of determine which cation is present. Draw a flow chart showing the procedure and the observations to be expected at each step with each of the possible cations. Write balanced equations for the following chemical reactions. State the color the products for each reaction. Cd^+2 _(aq) + S^-2 _(aq) rightarrow SnS_2(S) + OH^- _(aq) rightarrow Cu^+2 _(aq) + NH_3(aq) rightarrow

Explanation / Answer

Q1-

H2S is a hazardous material, it forms lots of fumes which are toxi (odor is similar to rotten eggs) Also, it can irritate eyes and skin,

In solution, this is an acid, so pH is low, it is reactive, so this must be away from bases and other reacitve material.

Q2.

Group 2 cations:

Hg2+, Bi3+ , Cu2+ , Cd2

Typically, we add H2S in acidic solution so they will preicpitate as Sulfide metals

Then we add HNO3, since Nitrates are soluble, mostly

HgS is not soluble, so you can filter this already

Then, we add NH3 in basic media in order to favour Hydroxide precipitation

Bi(OH)3, Cu(OH). Cd(OH)2 form

Then, much more NH3 is added in order to form complexes:

Cu(NH3)4(NO3)2 and Cd(NH3)4(OH)2

Now, Bi will not form complex, so filter this and you get Bismuth alone

the new complexes:

Cu(NH3)4(NO3)2 + 10KCN + H2O ---> 2K3[Cu(CN)4] + 4KNO3 + NH4CN + NH4CNO + 6NH3

There is copper Cyanide complex formation

Cd(NH3)4(OH)2 + 4 KCN K2[Cd(CN)4] + 4 NH3 + 2 KOH

Then Addition of H2S once again will give

CdS precipitate only, so you have compelted the separation of species

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