Question

U U DEU Methyl violet to be in an acidic solution? tretet qellow at color do you expect methyl violet to be in a basic solution? Orange Blue POST-LAB QUESTIONS PART A 1. Why did the color change when you added the concentrated HCl to the CoCl2-6 H2O2 e 2. Why did the color change when you diluted the solution? 3. Is Reaction 1 endothermic or exothermic? Explain your choice. PART B 4. Explain why the reagent you used in Step 6 caused the solution to change color. 5. Explain why the reagent you used in Step 7 caused the solution to change color. PART C

Answer 1

PART A

Q1:-

The main species involved in the reaction is cobalt (II) chloride, or CoCl2, which usually comes in the form of a hexahydrate, CoCl2⋅6H2O. When dissolved in water, both CoCl2, and CoCl2⋅6H2O will produce the complex ion [Co(H2O)6]2+.and when we add HCl it will react in following manner

[Co(H2O)6]2+ +4Cl-⇌ CoCl24-+6H2O

The [Co(H2O)6]2+ ion is pink, while the CoCl24- ion is blue.

Q2:-

When we dilute the solution its pH will change and hence the color will change.Further, the equilibrium will shift to the left and the color will be pink. If you add HCl, which will increase the concentration of Cl− ions, the equilibrium will shift to the right and the color will be blue.

Q3:-

The forward reaction is endothermic, which means the equilibrium could be written as

[Co(H2O)6]2+ +4Cl- + Heat⇌ CoCl24-+6H2O

We can say that heat is a reactant in this equilibrium. This means that when heat is added, i.e. the solution is being heated, the equilibrium will shift in the direction of the products. This shift in the equilibrium will turn the solution blue, the color of the CoCl24- ion.