Equilibrium position -- a + b = c -- effect of dilution
iodine is sparingly soluble in pure water. however, it does `dissolve' in solutions containing excess iodide ion because of the following reaction: i-(aq) + i2(aq)= i3-(aq) k = 710. for each of the following cases calculate the equilibrium ratio of [i3-] to [i2]. 6.00×10-2 mol of i2 is added to 1.00 l of 6.00×10-1 m ki solution.
the solution above is diluted to

299

Explanation:

The initial concentrations are:

[I₂] = 6.00 × 10⁻² mol / 1.00 L = 6.00 × 10⁻² M

[KI] = [I⁻] = 6.00 × 10⁻¹ M

We can find the concentrations at equilbrium using an ICE chart.

       I⁻(aq)          +           I₂(aq)           ⇄           I₃⁻(aq)

I    6.00 × 10⁻¹            6.00 × 10⁻²                    0

C       -x                             -x                             x

E  6.00 × 10⁻¹-x         6.00 × 10⁻²-x                   x

The equilibrium constant (K) is:

Solving the quadratic equation, we get the feasible x = 0.0598

The ratio [I₃⁻] to [I₂] is 0.0598 / 2.00 × 10⁻⁴ = 299.

If we diluted the initial mixture to, for instance, 10.0 L (dilution 1:10),

The initial concentrations are:

[I₂] = 6.00 × 10⁻³ M

[KI] = [I⁻] = 6.00 × 10⁻² M

We can find the concetrations at equilbrium using an ICE chart.

       I⁻(aq)          +           I₂(aq)           ⇄           I₃⁻(aq)

I    6.00 × 10⁻²            6.00 × 10⁻³                    0

C       -x                             -x                             x

E  6.00 × 10⁻²-x         6.00 × 10⁻³-x                   x

The equilibrium constant (K) is:

Solving the quadratic equation, we get the feasible x = 0.00585

The ratio [I₃⁻] to [I₂] is 0.00585 / 1.50 × 10⁻⁴ = 39. The solubility of I₂ decreases.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

plasma - state of matter made up of electrically charged particles