A student finds that 24.52 mL of 0.7170 M silver nitrate is needed to precipitate all of the bromide ion in a 50.00-mL sample of an unknown. What is the molarity of the bromide ion in the student's unknown?

Respuesta :

Answer: The molarity of bromide ions is 0.348 M.

Explanation:

To calculate the moles of cadmium nitrate, we use the equation:

[tex]\text{Molarity of the solution}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}[/tex]       .....(1)

Molarity of silver nitrate = 0.7170 M

Volume of silver nitrate = 24.52 mL = 0.02452 L   (Conversion factor: 1 L = 1000 mL)

Putting values in equation 1, we get:

[tex]0.7170mol/L=\frac{\text{Moles of silver nitrate}}{0.02425L}\\\\\text{Moles of silver nitrate}=0.0174mol[/tex]

The chemical equation for the reaction of silver nitrate and bromide ions follows:

[tex]AgNO_3(aq.)+Br^-(aq.)\rightarrow AgBr(s)+NO_3^-(aq.)[/tex]

By Stoichiometry of the reaction:

1 mole of silver nitrate reacts with 1 mole of bromide ions.

So, 0.0174 moles of silver nitrate will react with = [tex]\frac{1}{1}\times 0.0174=0.0174mol[/tex] of bromide ions.

Now, calculating the molarity of bromide ions by using equation 1, we get:

Moles of bromide ions = 0.0174 moles

Volume of solution = 50 mL = 0.05 L

Putting values in equation 1, we get:

[tex]\text{Molarity of bromide ions}=\frac{0.0174mol}{0.05L}=0.348M[/tex]

Hence, the molarity of bromide ions is 0.348 M.