Calculate the molality of a solution prepared by dissolving 225.5 g KNO3 in 825mL of water. Show your work

molality m=moles solute/kg of solvent

= 225.5/(101.1*.825)

note: 825ml water has a mass of .825kg

To calculate the molality of a solution, we need to know the mass of the solute (in this case, potassium nitrate, KNO3) and the mass of the solvent (in this case, water). We also need to convert the volume of the solvent from milliliters (mL) to kilograms (kg). Here's how you can calculate the molality:

Step 1: Convert the volume of water from mL to kg.
To do this, we need to remember that 1 mL of water has a mass of 1 gram. Since the density of water is approximately 1 g/mL, we can assume that 825 mL of water has a mass of 825 grams. To convert grams to kilograms, we divide by 1000:
825 grams ÷ 1000 = 0.825 kg

Step 2: Calculate the molality.
Molality (m) is defined as the moles of solute (n) divided by the mass of the solvent in kg (m):
m = n / m

To find the moles of solute, we need to know the molar mass of KNO3. The molar mass of KNO3 is calculated by summing the atomic masses of the elements in the compound:
- The atomic mass of K (potassium) is 39.10 g/mol.
- The atomic mass of N (nitrogen) is 14.01 g/mol.
- The atomic mass of O (oxygen, which appears three times in KNO3) is 16.00 g/mol.

Molar mass of KNO3: (1 x 39.10 g/mol) + (1 x 14.01 g/mol) + (3 x 16.00 g/mol) = 101.10 g/mol

Next, we calculate the moles of solute:
moles of KNO3 = mass of KNO3 / molar mass of KNO3
moles of KNO3 = 225.5 g / 101.10 g/mol

Step 3: Plug the values into the formula.
m = (moles of KNO3) / (mass of water in kg)
m = moles of KNO3 / 0.825 kg

Now, you can calculate the molality.
Remember to round off the answer to an appropriate number of significant figures.