A solution is prepared by dissolving 10.00g of a monobasic salt in a total volume of 1.00litres. Th pH of this solution was measured at 13.07 and a conductivity experiment determined that this salt was completely ionized in solution. What is the molecular weight of this monobasic salt?
To find the molecular weight of the monobasic salt, we need to use the data given - the mass of the salt and the volume of the solution - along with the fact that the salt is completely ionized in solution.
Since the salt is monobasic, it will dissociate into one ion of its constituent elements in solution. In this case, let's assume it dissociates into a monovalent cation and a monovalent anion.
Given that the solution has a volume of 1.00 liter, we can convert this volume to grams using the density of water, which is 1 gram per milliliter, or 1000 grams per liter.
1 liter of water = 1000 grams
Next, we need to find the number of moles of the salt dissolved in the solution. To do this, we divide the mass (in grams) of the salt by its molar mass (in grams/mole).
Using the formula:
moles of solute = mass of solute / molar mass of solute
we can rearrange to solve for the molar mass:
molar mass of solute = mass of solute / moles of solute
In this case, we know the mass of the solute (10.00 grams) and we need to find the moles of the solute.
Given that the salt is completely ionized in solution, the number of moles of the solute will be equal to double the concentration of ions in solution.
To find the concentration of ions in solution, we can use pH. The pH scale is a measure of the hydrogen ion concentration in a solution. A pH of 13.07 indicates a strongly basic solution, which means a high concentration of hydroxide ions (OH-) in solution.
To convert the pH to a concentration of hydroxide ions, we can use the formula:
[H+] = 10^(-pH)
In this case, we need to find the concentration of hydroxide ions ([OH-]), which is equal to the concentration of the anion of the salt.
Given that the salt is monobasic, we assume it dissociates into a monovalent anion. Therefore, the concentration of the anion will be equal to the concentration of hydroxide ions.
Now, we can use the concentration of the anion to find the moles of the solute.
moles of solute = concentration of anion x volume of solution
Substituting the values we have:
moles of solute = [OH-] x volume of solution
Since we know the volume of the solution is 1.00 liter and we don't have a specific concentration value, we can simplify the equation to:
moles of solute = [OH-]
Now, we can substitute this value into the formula for molar mass:
molar mass of solute = mass of solute / moles of solute
molar mass of solute = 10.00 grams / [OH-]
Finally, we can calculate the molar mass of the monobasic salt using the given pH of 13.07, which corresponds to the concentration of hydroxide ions.
Therefore, to find the molecular weight of this monobasic salt, we need to calculate the concentration of hydroxide ions from the pH and use it in the formula to find the molar mass.