Achemist prepares a solution of iron chloride by measuring out of into a volumetric flask and filling to the mark with distilled water. calculate the molarity of anions in the chemist's solution.

Complete Question:

A chemist prepares a solution of iron chloride by measuring out 0.10 g of FeCl2 into a 50. mL volumetric flask and filling to the mark with distilled water. Calculate the molarity of anions in the chemist's solution.

[Fe+] = 0.0156 M

[Cl-] = 0.0316 M

Explanation:

The molar mass of iron chloride is 126.75 g/mol, thus, the number of moles presented in 0.10 g of it is:

n = mass/molar mass

n = 0.10/126.75

n = 7.89x10⁻⁴ mol

In a solution, it will dissociate to form:

FeCl2 -> Fe+  + 2Cl-

So, the stoichiometry is 1:1:2, and the number of moles of the ions formed are:

nFe+ = 7.89x10⁻⁴ mol

nCl- = 2*7.89x10⁻⁴  = 1.58x10⁻³ mol

The molarity is the number of moles divided by the solution volume, in L (50.0 mL = 0.05 L):

[Fe+] = 7.89x10⁻⁴/0.05 = 0.0156 M

[Cl-] = 1.58x10⁻³/0.05 = 0.0316 M

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.

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