Calculate molarity of KNO3 solution if 69 g of salt are dissolved into 250 mL of solution
M=69/formulamassKNO3 /.250
To calculate the molarity of a solution, you need to know the amount of solute (in moles) and the volume of the solution (in liters). Let's calculate the molarity of the KNO₃ solution using the given information.
Step 1: Convert the mass of KNO₃ to moles.
To do this, you need the molar mass of KNO₃, which can be found by adding up the atomic masses of the elements:
- 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) is 16.00 g/mol.
Molar mass of KNO₃ = (1 × atomic mass of K) + (1 × atomic mass of N) + (3 × atomic mass of O)
= (1 × 39.10 g/mol) + (1 × 14.01 g/mol) + (3 × 16.00 g/mol)
= 39.10 g/mol + 14.01 g/mol + 48.00 g/mol
= 101.11 g/mol
Using the given mass of KNO₃ (69 g), you can calculate the number of moles:
Number of moles = mass / molar mass
= 69 g / 101.11 g/mol
≈ 0.682 mol
Step 2: Convert the volume of the solution from mL to L.
Given volume = 250 mL, which can be converted to liters by dividing by 1000:
Volume of solution = 250 mL / 1000 mL/L
= 0.250 L
Step 3: Calculate molarity.
Molarity (M) is defined as moles of solute divided by volume of solution in liters:
Molarity = moles of solute / volume of solution
= 0.682 mol / 0.250 L
≈ 2.73 M
Therefore, the molarity of the KNO₃ solution is approximately 2.73 M.