Question

In lab we tested for unknown compounds. I identified my unknown compound was CaCl2. Post lab question is asking what additional tests could I have done to further help identify my unknown compound (CaCl2)

Answer 1

If you already knew that your unknown sample is CaCl₂. Then you simply perform the confirmatory tests for Calcium and Chloride separately and confirm their presence in your solution.

Tests for Calcium:

1. Simple test is the flame test. Alkali metals and alkali earth metals show different colors when they are exposed to flame. so when you expose your calcium salt into bunsen burner. It will show you brick red color which is also green in color when seen through blue glass. It is the confirmatory flame test for calcium.

2. Ca²⁺is the member of group V. You can precipitate any group V ions into their carbonates. When (NH₄)₂CO₃ is added to the solution of your calcium chloride containing NH₄Cl and NH₄OH. You will see Calcium carbonate white ppt.

CaCl₂ + (NH4)₂CO₃ = CaCO₃ + 2NH₄Cl

Tests for chlorine:

1. The simple test for chloride confirmation is precipitation test. if you add little amount of silver nitrate solution to your calcium chloride solution, you will see curdy white ppt. of AgCl.

2AgNO₃ + CaCl₂ = 2AgCl + Ca(NO₃)₂

2. You can also perform chloride conformation as dry chloride. Mix your solid CaCl₂ with an equal weight of manganese dioxide then moisten with sulfuric acid, and gently heat the mixture. Chlorine gas will evolve from the mixture which can be confirmed by moistened starch iodine paper. if you keep an moisten starch iodine paper in the way of chlorine gas, you will see a production of blue color in your starch paper. It is the confirmatory test for chloride.