Here's how to separate the given mixtures, illustrated with flowcharts:
a) NH₄Cl from SiO₂:
Flowchart:
```
Mixture: NH₄Cl + SiO₂
↓
Heat the mixture | SiO₂ does not sublimate
↓
NH₄Cl sublimates |
↓
Collect the solid | SiO₂ remains as residue
↓
NH₄Cl (sublimed)
```
Explanation:
* Sublimation: Ammonium chloride (NH₄Cl) readily sublimes (changes directly from solid to gas) when heated. Silicon dioxide (SiO₂) does not.
* Separation: By heating the mixture, NH₄Cl vaporizes, leaving behind solid SiO₂. The NH₄Cl vapor is then collected and cooled to solidify again, resulting in pure NH₄Cl.
b) Iodine (I₂) from Sand:
Flowchart:
```
Mixture: I₂ + Sand
↓
Heat the mixture | Sand does not sublimate
↓
I₂ sublimates |
↓
Collect the solid | Sand remains as residue
↓
I₂ (sublimed)
```
Explanation:
* Sublimation: Iodine (I₂) sublimes when heated, changing from solid to gas. Sand (SiO₂) does not.
* Separation: By heating the mixture, I₂ vaporizes, leaving behind solid sand. The I₂ vapor is then collected and cooled to solidify again, resulting in pure I₂.
Important Note: Both methods require careful control of the heating process to avoid any unwanted reactions or decomposition.
