80.0 grams of KBr is mixed with sufficient water to prepare 1865 mL of solution. This solution is then mixed with 46.3 mL of 0.425 M KCl solution. 12 mL of this mixture is subsequently added to 61.0 mL of distilled water. Calculate the molarity of K+ ions in the final mixture? KBr and KCl dissolve in water according to the following processes.
KCl(s)+H2O(l) yields K+(aq)+Cl-(aq)
KBr(s)+H2O(l) yields K+(aq)+Br-(aq)
80g KBr/molar mass = moles KBr in 1865 mL.
Add moles KCl = M x L = 0.0463*0.425=??
Add mols KBr + moles KCl for total moles.
Add volume 1.865L + 0.0463L = total volume
Next step is to find how much is pulled from the solution. We took 12 mL; therefore, we took
moles in 12 mL = total moles x 12/total volume.
Then M = final mols/final volume in L.
To calculate the molarity of K+ ions in the final mixture, let's break down the problem step by step.
Step 1: Calculate the number of moles of KBr.
Given that you have 80.0 grams of KBr, we need to convert this mass to moles. The molar mass of KBr is 119 g/mol (potassium's atomic mass is 39 g/mol, and bromine's atomic mass is 80 g/mol), so the calculation is:
moles of KBr = mass of KBr / molar mass of KBr
moles of KBr = 80.0 g / 119 g/mol = 0.672 moles
Step 2: Calculate the concentration (molarity) of KBr solution.
The solution volume is given as 1865 mL. To convert this to liters, divide by 1000:
volume of KBr solution = 1865 mL / 1000 = 1.865 L
Molarity of KBr = moles of KBr / volume of KBr solution
Molarity of KBr = 0.672 moles / 1.865 L = 0.360 M
Step 3: Calculate the moles of K+ ions in the KBr solution.
Since KBr dissociates completely, each mole of KBr produces one mole of K+ ions.
moles of K+ ions = moles of KBr = 0.672 moles
Step 4: Calculate the number of moles of K+ ions added from the KCl solution.
The volume of the KCl solution added is given as 46.3 mL, which is 0.0463 L. The molarity of KCl solution is 0.425 M.
moles of K+ ions added = volume of KCl solution * molarity of KCl solution
moles of K+ ions added = 0.0463 L * 0.425 M = 0.01965 moles
Step 5: Calculate the moles of K+ ions in the final mixture.
The moles of K+ ions in the final mixture are the sum of the moles from the KBr solution and the moles added from the KCl solution.
moles of K+ ions in final mixture = moles of K+ ions from KBr solution + moles of K+ ions added from KCl solution
moles of K+ ions in final mixture = 0.672 moles + 0.01965 moles = 0.69165 moles
Step 6: Calculate the final volume of the mixture.
The final volume is the sum of the volumes of the diluted mixture and the added water.
final volume = 12 mL + 61.0 mL = 73.0 mL = 0.073 L
Step 7: Calculate the molarity of K+ ions in the final mixture.
Molarity of K+ ions = moles of K+ ions in final mixture / final volume
Molarity of K+ ions = 0.69165 moles / 0.073 L = 9.490 M