I had posted a while back and still couldn't solve this is there anyway you could show me the steps on how u did this? thank you very much
A solution is made by mixing 20.0 mL of toluene C6H5CH3d=0.867gmL with 150.0 mL of benzene C6H6d=0.874gmL.
Assuming that the volumes add upon mixing, what are the molarity (M) and molality (m) of the toluene
Dora--I scrolled back yesterday and noticed you had added some material but I also noticed a math error. I posted a correction but I don't know if you saw it or not. Here is the way you do the problem. Check my arithmetic very carefully.
mass 20.0 mL toluene = 20.0 x 0.867 = 17.34 grams (I think you had 17.9 something).
mols toluene = 17.34/92.14 = 0.188 mols toluene.
mass benzene = 150.0 mL x 0.874 = 131.1 grams = 0.1311 kg.
molality toluene = 0.188 mol/0.1311 kg solvent = 1.4355 m which I would round to 1.44 m to three s.f.
molarity toluene in benzene = mols toluene/total L of solution = 0.188 mols toluene/0.170 L solution (that's 150.0 mL + 20.0 mL = 170 mL) = 1.10588 which rounds to 1.11 to three s.f.
Check my thinking. Check my work.
thank you very much Dr. Bob
Certainly! To find the molarity (M) and molality (m) of the toluene in the solution, we will need to calculate the moles of toluene first.
The molarity (M) is defined as the number of moles of solute (in this case, toluene) per liter of solution. The formula for calculating molarity is:
Molarity (M) = moles of solute / volume of solution in liters
Step 1: Calculate the moles of toluene.
We can calculate the moles of toluene by using its density. The formula to calculate moles is:
moles = density (g/mL) x volume (mL) / molar mass (g/mol)
The molar mass of toluene (C7H8) is 92.14 g/mol.
moles of toluene = density of toluene x volume of toluene / molar mass of toluene
= 0.867 g/mL x 20.0 mL / 92.14 g/mol
Step 2: Calculate the total volume of the solution.
Since the volumes add upon mixing, we can simply sum the volumes of toluene and benzene.
volume of solution = volume of toluene + volume of benzene
= 20.0 mL + 150.0 mL
Now, we need to convert the total volume from milliliters (mL) to liters (L) in order to calculate the molarity.
Step 3: Convert the volume of the solution from mL to L.
1 L is equal to 1000 mL, so we can divide the volume of the solution by 1000 to get the volume in liters.
volume of solution (in liters) = (20.0 mL + 150.0 mL) / 1000
Step 4: Calculate the molarity.
Finally, we can calculate the molarity using the moles of toluene and the volume of the solution (in liters).
Molarity (M) = moles of toluene / volume of solution (in liters)
Step 5: Calculate the molality (m).
The molality (m) is defined as the number of moles of solute (in this case, toluene) per kilogram of solvent (in this case, benzene). The formula for calculating molality is:
Molality (m) = moles of solute / mass of solvent (in kg)
Since we are given the density of benzene (0.874 g/mL), we can calculate the mass of benzene using its volume (in mL). The formula to calculate mass is:
mass = density (g/mL) x volume (mL)
mass of benzene = density of benzene x volume of benzene
= 0.874 g/mL x 150.0 mL
Finally, we can convert the mass of benzene from grams (g) to kilograms (kg) by dividing by 1000.
mass of solvent (benzene) = 0.874 g/mL x 150.0 mL / 1000
Now, we can calculate the molality using the moles of toluene and the mass of benzene (in kg).
Molality (m) = moles of toluene / mass of solvent (benzene) (in kg)
By following these steps and substituting the given values into the formulas, you will be able to find the molarity (M) and molality (m) of toluene in the solution.