You have three ammonium sulfate solutions on a lab table in front of you. All of the solutions came from a 500.0-mL volumetric flask containing 3.00 M ammonium sulfate. Solution 1 contains 127.2 mL of the 3.00 M solution.
Solution 2 contains 68.7 mL of the 3.00 M solution.
Solution 3 contains 32.4 mL of the 3.00 M solution.
How many moles of ions does Solution 2 contain?
A) 0.206 mol
B) 1.44 mol
C) 0.618 mol
D) 0.412 mol
E) 0.309 mol

Question

Quizplus · Accepted Answer

First, we need to calculate the number of moles in each solution. We can do this using the formula:

moles = concentration x volume (in liters)

For Solution 1:
moles = 3.00 M x 0.1272 L = 0.3816 mol

For Solution 2:
moles = 3.00 M x 0.0687 L = 0.2061 mol

For Solution 3:
moles = 3.00 M x 0.0324 L = 0.0972 mol

Next, we need to calculate the number of moles of ions in Solution 2. Ammonium sulfate dissociates into two ions when it is dissolved in water: ammonium ions (NH4+) and sulfate ions (SO42-). Therefore, the number of moles of ions in Solution 2 is:

moles of NH4+ ions + moles of SO42- ions

We can calculate the number of moles of each ion using the formula:

moles of ions = moles of solute x number of ions produced by solute

For ammonium ions (NH4+):
moles of NH4+ ions = 0.2061 mol x 1 = 0.2061 mol

For sulfate ions (SO42-):
moles of SO42- ions = 0.2061 mol x 1 = 0.2061 mol

Therefore, the total number of moles of ions in Solution 2 is:
moles of NH4+ ions + moles of SO42- ions = 0.2061 mol + 0.2061 mol = 0.4122 mol

However, we need to remember that we are looking for the number of moles of ions, not the total number of moles. This means that we need to divide by 2, since each mole of ammonium sulfate produces two moles of ions. Therefore, the final answer is:

0.4122 mol / 2 = 0.2061 mol

So the answer is (C) 0.618 mol.

You Have Three Ammonium Sulfate Solutions on a Lab Table