A solution is made by mixing 20.0 mL of C6H5CH3, d=.867g/mL, with 140.0mL of C6H6, d=.874g/mL. assuming that the volumes add upon mixing, what is the molarity? what is the molality?
i know that molarity= moles/L and molality= moles sol/kg solvent... but im not sure which numbers to use... help please
Using the density of each calculate the mass of each material used.
From the mass of each calculate the number of moles of each.
Add the two volumes to get the total volume, and you can now calculate the molarity of each.
Add the two masses and you can now calculate the molality of each.
A tip...don't forget leading zeros
e.g. d=0.867g/mL is clearer than d=.867g/mL
To calculate the molarity and molality of the solution, follow these steps:
1. Calculate the mass of C6H5CH3 (toluene):
mass = volume x density = 20.0 mL x 0.867 g/mL = 17.34 g
2. Calculate the mass of C6H6 (benzene):
mass = volume x density = 140.0 mL x 0.874 g/mL = 122.36 g
3. Calculate the number of moles of C6H5CH3:
moles = mass / molar mass = 17.34 g / molar mass of C6H5CH3
4. Calculate the number of moles of C6H6:
moles = mass / molar mass = 122.36 g / molar mass of C6H6
5. Add the volumes of C6H5CH3 and C6H6 to get the total volume of the solution. In this case, it is 160.0 mL.
6. Calculate the molarity (moles per liter) of each component:
molarity of C6H5CH3 = moles of C6H5CH3 / total volume in L
molarity of C6H6 = moles of C6H6 / total volume in L
7. Calculate the molality (moles per kilogram) of each component:
molality of C6H5CH3 = moles of C6H5CH3 / mass of C6H5CH3 in kg
molality of C6H6 = moles of C6H6 / mass of C6H6 in kg
Remember to convert the mass to kilograms before calculating molality.
Note: To calculate the molar masses of C6H5CH3 and C6H6, you can refer to the periodic table and add up the atomic weights of the elements involved.