Calculate the molarity of a solution made by adding 28.2 mL of concentrated ammonia (28.0 % by mass, density 0.880 g/mL) to some water in a volumetric flask, then adding water to the mark to make exactly 500 mL of solution. (It is important to add concentrated acid or base to water, rather than the other way, to minimize splashing and maximize safety.)
First we get the mass of NH3 (ammonia) in the concentrated NH3 solution, by using the relationship between density, mass and volume:
d = m/V
0.88 = m/28.2
m = 24.816 g
Since ammonia is only 28% of this mass,
m,NH3 = 24.816 * 0.28
m,NH3 = 6.9485 g NH3
Then we change this to moles. To change this to moles, we divide this mass by the molar mass of NH3. To get the molar mass, just get a periodic table and add the individual masses of the elements in the chemical formula:
Molar Mass of NH3: 1*14 + 3*1 = 17 g/mol
n,NH3 (moles of NH3) = 6.9485 / 17
n,NH3 = 0.4087 mol NH3
Finally, recall that molarity is just moles of solute per liter of solution,
M = n/V
Therefore, (500 mL = 0.5 L)
M = 0.4087 mol NH3 / 0.5 L
M = 0.817 M
Hope this helps~ :3
To calculate the molarity of the solution, we first need to determine the number of moles of ammonia in the 28.2 mL sample. Here's how we can do that:
Step 1: Calculate the mass of the ammonia in the 28.2 mL sample.
Given:
- Concentration of ammonia = 28.0% by mass
- Density of ammonia solution = 0.880 g/mL
- Volume of ammonia solution = 28.2 mL
First, let's calculate the mass of the ammonia in the solution:
Mass of ammonia = volume x density
Mass of ammonia = 28.2 mL x 0.880 g/mL
Step 2: Convert the mass of ammonia to moles.
To convert the mass of ammonia to moles, we need to know the molar mass of ammonia (NH3).
Molar mass of NH3 = 14.01 g/mol (nitrogen) + 1.01 g/mol (hydrogen) x 3
Molar mass of NH3 = 17.03 g/mol
Now we can calculate the moles of ammonia:
Moles of ammonia = mass of ammonia / molar mass of NH3
Step 3: Calculate the molarity of the solution.
To calculate the molarity (M) of the solution, we divide the moles of ammonia by the volume of the solution in liters.
Molarity = moles of ammonia / volume of solution (in liters)
Molarity = moles of ammonia / 0.500 L
Now let's put it all together:
1. Calculate the mass of ammonia:
Mass of ammonia = 28.2 mL x 0.880 g/mL
2. Convert the mass of ammonia to moles:
Moles of ammonia = Mass of ammonia / molar mass of NH3
3. Calculate the molarity of the solution:
Molarity = Moles of ammonia / 0.500 L
To calculate the molarity of the ammonia solution, we need to first determine the number of moles of ammonia present in the solution. Then, we can divide this by the volume of the solution in liters to find the molarity.
Here's how we can calculate it step by step:
Step 1: Calculate the number of moles of ammonia.
To do this, we need to find the mass of ammonia present in 28.2 mL of the concentrated solution.
Given:
- Concentration of ammonia: 28.0% by mass
- Density of ammonia solution: 0.880 g/mL
- Volume of ammonia solution added: 28.2 mL
Using the density and volume, we can calculate the mass of the ammonia solution added:
Mass = density x volume = 0.880 g/mL x 28.2 mL
Step 2: Calculate the mass of ammonia.
Since the concentration of ammonia is given as a percentage by mass, we need to find the mass of ammonia in the solution.
Mass of ammonia = (28.0/100) x mass of ammonia solution added
Step 3: Convert the mass of ammonia to moles.
To convert the mass of ammonia to moles, we need the molar mass of ammonia (NH₃).
Molar mass of NH₃ = 14.01 g/mol (N) + 3 * 1.01 g/mol (H)
Step 4: Calculate the number of moles of ammonia.
Number of moles of ammonia = Mass of ammonia / Molar mass of ammonia
Step 5: Calculate the molarity of the ammonia solution.
Finally, we can calculate the molarity by dividing the number of moles of ammonia by the volume of the solution in liters.
Molarity = Number of moles of ammonia / Volume of solution in liters (convert 500 mL to liters)
Now, you can follow these steps using the given values to find the molarity of the ammonia solution.