At 20°C, an aqueous solution that is 18.0% by mass in ammonium chloride has a density of 1.0512 g/mL What is the molarity of ammonium chloride in the solution?

18% w/w means 18g NH4Cl/100 g solution.

mols NH4Cl = grams/molar mass = ?
Convert 100 g solution to L using density; then M = mols/L.

To find the molarity of ammonium chloride in the solution, we need to calculate the number of moles of ammonium chloride present in the solution.

Step 1: Calculate the mass of the solution.
Since the density of the solution is given as 1.0512 g/mL, we can assume that 1 mL of the solution has a mass of 1.0512 grams.
Let's assume we have 100 grams of the solution.

Step 2: Calculate the mass of ammonium chloride in the solution.
Since the solution is 18.0% by mass in ammonium chloride, we calculate the mass of ammonium chloride as:
Mass of ammonium chloride = 18.0% of 100 grams
Mass of ammonium chloride = 0.18 * 100 grams
Mass of ammonium chloride = 18 grams

Step 3: Calculate the number of moles of ammonium chloride.
To find the number of moles, we divide the mass of ammonium chloride by its molar mass.
The molar mass of ammonium chloride (NH4Cl) can be calculated as:
Molar mass of ammonium chloride (NH4Cl) = (1 * Atomic mass of N) + (4 * Atomic mass of H) + (1 * Atomic mass of Cl)
Molar mass of ammonium chloride (NH4Cl) = (1 * 14.01 g/mol) + (4 * 1.01 g/mol) + (1 * 35.45 g/mol)
Molar mass of ammonium chloride (NH4Cl) = 53.49 g/mol

Now, we can calculate the number of moles of ammonium chloride as:
Number of moles = Mass of ammonium chloride / Molar mass of ammonium chloride
Number of moles = 18 grams / 53.49 g/mol
Number of moles = 0.3367 moles

Step 4: Calculate the volume of the solution in liters.
Since we assumed we have 100 grams of the solution and the density is given as 1.0512 g/mL, we can calculate the volume as:
Volume = Mass / Density
Volume = 100 grams / 1.0512 g/mL
Volume = 95.09 mL

Converting mL to liters:
Volume = 95.09 mL * (1 L / 1000 mL)
Volume = 0.09509 L

Finally, Step 5: Calculate the molarity of ammonium chloride.
Molarity (M) = Number of moles / Volume in liters
Molarity (M) = 0.3367 moles / 0.09509 L
Molarity (M) = 3.54 M

Therefore, the molarity of ammonium chloride in the solution is 3.54 M.

To find the molarity of ammonium chloride in the solution, we need to take the mass percentage and convert it to molarity.

First, we need to determine the mass of ammonium chloride present in the solution. To do this, we'll assume we have 100 grams of the solution (since the mass percentage is given as a percentage by mass). This means we have 18 grams of ammonium chloride (100 grams x 18.0%).

Next, we'll calculate the moles of ammonium chloride using its molar mass. The molar mass of ammonium chloride (NH4Cl) is 53.49 g/mol. Therefore, the number of moles of ammonium chloride in the solution is:

moles of NH4Cl = mass of NH4Cl / molar mass of NH4Cl
= 18 g / 53.49 g/mol
= 0.34 mol

Finally, we calculate the volume of the solution using its density. The density of the solution is given as 1.0512 g/mL, which means that 1 mL of the solution has a mass of 1.0512 grams.

Since we have 100 grams of the solution, the volume is:

volume of solution = mass of solution / density of solution
= 100 g / 1.0512 g/mL
= 95.20 mL

Now, we can calculate the molarity of ammonium chloride:

Molarity = moles of solute / volume of solution (in liters)
= 0.34 mol / (95.20 mL / 1000 mL/L)
= 0.34 mol / 0.09520 L
= 3.57 M

Therefore, the molarity of ammonium chloride in the solution is 3.57 M.