Question

Find the molarity of iodide ions in a solution obtained by dissolving 1.97 g of ZnI2(s) and enough water to form 34.2 mL of solution. Assume complete dissociation of ZnI2(aq) into ions. The molar mass of ZnI2 is 319.22 g/mol. Give the answer in mol/L with 3 or more significant figures.

Answer 1

Answer: The molarity of iodide ions in given solution is 0.181 M.

Step-by-step explanation:

Given: Mass = 1.97 g

Volume = 34.2 mL (1 mL = 0.001 L) = 0.0342 L

Molar mass of
`ZnI_(2)` = 319.22 g/mol

Moles is the mass of substance divided by its molar mass. Hence, moles of
`ZnI_(2)` are calculated as follows.

`Moles = (mass)/(molar mass)\\= (1.97 g)/(319.22 g/mol)\\= 0.0062 mol`

Molarity is the number of moles of a substance present in liter of a solution.

So, molarity of given solution is calculated as follows.

`Molarity = (moles)/(Volume (in L))\\= (0.0062 mol)/(0.0342 L)\\= 0.181 M`

Thus, we can conclude that molarity of iodide ions in given solution is 0.181 M.