To calculate the molar mass of the unknown substance, we need to use the formula:
Molar mass = (mass of solute) / (number of moles of solute)
First, let's calculate the number of moles of solute in the solution:
Number of moles = (concentration) x (volume in liters)
We know that the concentration of the solution is 0.45 M, and the volume of the solution is 425 mL, which is equivalent to 0.425 L. Substituting these values into the formula, we get:
Number of moles = 0.45 M x 0.425 L
Number of moles = 0.19125 moles
Next, we can calculate the mass of the solute (the unknown substance) by using the formula:
mass = number of moles x molar mass
Rearranging the formula, we get:
molar mass = mass / number of moles
We know that the mass of the solute is 12 grams, and we have already calculated the number of moles as 0.19125 moles. Substituting these values into the formula, we get:
molar mass = 12 g / 0.19125 moles
molar mass = 62.8 g/mol
Therefore, the molar mass of the unknown substance is 62.8 g/mol.