Answer:
The molarity of K+ ions is 2.67 M, the molarity of PO43- ions is 0.89 M, and the molarity of K3PO4 is 0.89 M.
Step-by-step explanation:
The first step in solving this problem is to determine the number of moles of potassium phosphate in 18.9 g. We can do this by dividing the mass by the molar mass:
molar mass of K3PO4 = (3 x atomic mass of K) + atomic mass of P + (4 x atomic mass of O)
= (3 x 39.10 g/mol) + 30.97 g/mol + (4 x 16.00 g/mol)
= 212.27 g/mol
moles of K3PO4 = 18.9 g / 212.27 g/mol
= 0.089 mol
Next, we need to determine the molarity of each species in the solution. K3PO4 dissociates in water to form three K+ ions and one PO43- ion. Therefore, the molarity of K+ ions, PO43- ions, and K3PO4 in the solution are:
Molarity of K+ ions = (3 x moles of K3PO4) / volume of solution
= (3 x 0.089 mol) / 0.100 L
= 2.67 M
Molarity of PO43- ions = (1 x moles of K3PO4) / volume of solution
= (1 x 0.089 mol) / 0.100 L
= 0.89 M
Molarity of K3PO4 = moles of K3PO4 / volume of solution
= 0.089 mol / 0.100 L
= 0.89 M
Therefore, the molarity of K+ ions is 2.67 M, the molarity of PO43- ions is 0.89 M, and the molarity of K3PO4 is 0.89 M.
For more help:
Here's a general outline:
Determine the number of moles of solute in the solution. This requires you to know the mass of the solute and its molar mass, which can be found on the periodic table.
Convert the volume of the solution to liters. This is important because molarity is defined as the number of moles of solute per liter of solution.
Calculate the molarity of the solution using the formula:
Molarity = moles of solute / liters of solution
Be sure to use the correct number of moles of solute and volume of solution in the formula.
If the solute dissociates in water to form ions, determine the molarity of each ion. This requires you to know the stoichiometry of the dissociation reaction, which can be found in chemical formulas or equations.
If the problem asks for the concentration of a specific ion or species, use the appropriate formula to calculate its molarity based on the molarity of the solute or dissociated ions.
Here's an example problem to illustrate these steps:
What is the molarity of a solution made by dissolving 10.0 g of sodium chloride, NaCl, in enough water to make 500.0 mL of solution?
Step 1: Determine the number of moles of NaCl in the solution.
The molar mass of NaCl is the sum of the atomic masses of sodium and chlorine:
molar mass of NaCl = 22.99 g/mol + 35.45 g/mol = 58.44 g/mol
The number of moles of NaCl can be calculated using the formula:
moles of NaCl = mass of NaCl / molar mass of NaCl
moles of NaCl = 10.0 g / 58.44 g/mol = 0.171 mol
Step 2: Convert the volume of the solution to liters.
500.0 mL = 0.5000 L
Step 3: Calculate the molarity of the solution.
Molarity = moles of solute / liters of solution
Molarity = 0.171 mol / 0.5000 L = 0.342 M
The molarity of the NaCl solution is 0.342 M.
Step 4: Determine the molarity of each ion.
NaCl dissociates in water to form one Na+ ion and one Cl- ion, so the molarity of each ion is:
Molarity of Na+ = 0.171 mol / 0.5000 L = 0.342 M
Molarity of Cl- = 0.171 mol / 0.5000 L = 0.342 M
Step 5: Calculate the molarity of a specific ion or species if required.
For example, if the problem asks for the molarity of Cl- ions only, you can use the molarity of NaCl and the stoichiometry of the dissociation reaction to calculate it:
Molarity of Cl- = Molarity of NaCl = 0.342 M
Hope any of this helps! If not, I'm sorry. If you need more help, ask me! :]