Achemist obtains 500.0 ml of a solution containing an unknown concentration of calcium iodide, cai2. he pipets 15 ml of this solution into a 100 ml volumetric flask and dilutes to the mark. he then pipettes 10 ml of this diluted solution into a 25 ml volumetric flask and dilutes to the mark. he analyzes some of the solution from the final volumetric flask and finds that the iodide ion concentration is 0.41 m. (note: in solution, calcium iodide breaks apart into one ca2+ ion for every two i- ions, so a solution that is 1.0 m in cai2 is 2.0 m in determine the molar concentration of calcium iodide in the original solution. latex: cai _{2} (s)→ ca^{ 2+}(aq)+2 i^{-}(aq)

3.41735M

Explanation:

Step1: Balance the equation

CaI2 (s) → Ca2+ (aq ) + 2I- (aq)

We have 15 mL of the original sample and pipet it in a 100mL solution.

100/15 = 6.67 ⇒ this is a 1:6.67 dilution

We take 10mL of this dilution into a 25 mL flask ⇒this is a 1:2.5 dilution

6.67 * 2.5 = 16.675

⇒the total dilution is 1:16.675  

Let's imagine the conc of CaI2 [CaI2] = 1M

⇒ 15mL of this 1M conc in a 100mL = 0.15M

⇒10mL of this 0.15 M in 25mL = 0.06M

1M original conc/ O.O6M final concentration = 16.67

⇒this means the dilution is 16.67 (1:16.67)

After analyzes we found that the iodide ion concentration = 0.41 M

⇒original conc / 0.41 M  = 16.67

original conc I- = 16.67 * 0.41M = 6.8347 M

Since we have one Ca2+ ion for every 2 I- ions, we have to divide this concentration by 2 to find  the [Ca2+]

6.8347 / 2 = 3.41735 M  =[Ca2+] = [CaI2]

The concentration calcium iodide = 3.41735M

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.

3 1/4 %

explanation: