what mass(g) of NH3 must be dissolved in 475g of methanol to make a 0.25m solution
Is that m as in molal.
m = mols solute/kg solvent
Substitute and solve for mol solute.
Then mols solute = grams solute/molar mass solute. Substitute and solve for grams solute (NH3)
To calculate the mass of NH3 needed to make a 0.25 M solution in 475 g of methanol, we need to consider the equation:
Molarity (M) = moles of solute / liters of solution
First, let's calculate the moles of NH3 needed for a 0.25 M solution:
0.25 M = moles of NH3 / liters of solution
Since we are not given the volume of the solution in liters, we need to assume that it is 1 liter for convenience:
0.25 M = moles of NH3 / 1 L
Now, let's calculate the moles of NH3:
moles of NH3 = 0.25 M × 1 L
Next, we need to convert the moles of NH3 to mass using the molar mass of NH3:
Molar mass of NH3 = 14.01 g/mol + (3 × 1.01 g/mol) = 17.03 g/mol
Now, let's calculate the mass of NH3:
mass of NH3 = moles of NH3 × molar mass of NH3
Finally, we substitute the values into the equation:
mass of NH3 = 0.25 M × 1 L × 17.03 g/mol
mass of NH3 = 0.25 × 1 × 17.03 g
mass of NH3 = 4.2575 g
Therefore, approximately 4.26 g of NH3 must be dissolved in 475 g of methanol to make a 0.25 M solution.
To find out the mass of NH3 that needs to be dissolved in methanol to make a 0.25 m (molar) solution, you'll need to use the formula:
moles of solute = molarity × volume of solution (in liters)
First, let's calculate the volume of the solution:
Given:
Mass of methanol (solvent) = 475 g
Density of methanol = 0.7918 g/mL (at room temperature)
Volume of methanol = mass / density = 475 g / 0.7918 g/mL ≈ 600.58 mL
Next, calculate the moles of NH3 required using the molarity and volume of the solution:
Given:
Molarity (molar concentration) = 0.25 mol/L (0.25 M)
Volume of methanol = 600.58 mL
Convert the volume of methanol to liters:
Volume of methanol = 600.58 mL / 1000 mL/L = 0.60058 L
Now, substitute the values into the formula:
moles of solute = (0.25 mol/L) × (0.60058 L) ≈ 0.1501 mol
Finally, determine the mass of NH3 by using its molar mass:
Molar mass of NH3 = 17.03 g/mol
Mass of NH3 = moles of NH3 × molar mass = 0.1501 mol × 17.03 g/mol ≈ 2.554 g
Therefore, approximately 2.554 grams of NH3 must be dissolved in 475 grams of methanol to make a 0.25 m solution.