By means of what single reagent could you distinguish between the following? (Tell what happens to each substance.)
Solutions:
AgNO3 and Zn(NO3)2
H2SO4 and HNO3
Ag(NH3)2Cl and AgNO3
Solids:
AgCl and ZnCl2
AgCl and Hg2Cl2
PbCrO4 and K2CrO4
To distinguish between the given solutions and solids, we can use various reagents that will cause unique chemical reactions or visual changes for each substance. Let's go through each case:
1. Solutions:
a. AgNO3 and Zn(NO3)2:
- Add Sodium Hydroxide (NaOH) solution to each test tube containing the solutions separately.
- AgNO3 will form a brown precipitate of AgOH.
- Zn(NO3)2 will not show any visible change because zinc hydroxide is amphoteric and dissolves in excess NaOH.
b. H2SO4 and HNO3:
- Add a piece of sugar (sucrose) to each test tube containing the solutions separately.
- H2SO4 will rapidly dehydrate the sugar, resulting in the production of black carbon and releasing sulfur dioxide gas (SO2).
- HNO3 will oxidize the sugar, forming brown nitrogen oxide fumes and leaving a black residue.
c. Ag(NH3)2Cl and AgNO3:
- Add Ammonia (NH3) solution to each test tube containing the solutions separately.
- AgNO3 will not show any visible change.
- Ag(NH3)2Cl will form a white precipitate of AgCl due to the replacement of NH3 with Cl-.
2. Solids:
a. AgCl and ZnCl2:
- Add Ammonia (NH3) solution to each solid separately.
- AgCl will dissolve in NH3 forming a colorless solution.
- ZnCl2 will not show any visible change.
b. AgCl and Hg2Cl2:
- Add Concentrated Ammonia (NH3) solution to each solid separately.
- AgCl will dissolve in NH3 forming a colorless solution.
- Hg2Cl2 will not show any visible change.
c. PbCrO4 and K2CrO4:
- Add Dilute Nitric Acid (HNO3) to each solid separately.
- PbCrO4 will dissolve in HNO3, forming a yellow solution due to the formation of lead (II) nitrate.
- K2CrO4 will not show any visible change.
By performing these tests with the appropriate reagents, you will be able to distinguish between the given substances based on their unique reactions or visual changes.
You're supposed to use your knowledge of chemistry to answer these.
The first one, AgNO3 and Zn(NO3)2.
Add NaCl. The AgNO3 reacts with NaCl to produce a white insoluble precipitate of AgCl. Zn(NO3)2 and NaCl does nothing. So the secret is to know the solubility tables. Where a ppt will not form, the usual test is something that produces a colored complex ion, or something similar.
For the solids.
Add H2O. AgCl is insoluble. ZnCl2 dissolves easily.
Now you try the others.