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
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* chemistry - DrBob222, Thursday, April 3, 2008 at 5:10pm
Use density to determine mass toluene, then convert mass to mols toluene.
Use density to determine mass 150.0 mL benzene,
Then molality toluene = #mols/kg solvent.
molarity = mols/L solution.
Post your work if you get stuck.
o chemistry - Dora, Thursday, April 3, 2008 at 6:43pm
i still got it wrong
0.867 g/mol= x/ 20 ml x= 17.94 g
0.874 g/mol= x/ 150 mil x= 131.1 g
toluene 17.904 g x 1 m/ 92.14 g/ mol= .194 m
benzee 131.1 g x 1m/78.1121 g/mol = 1.68 m
.194 m Toluene/ .1311 kg = 1.48
* chemistry - DrBob222, Friday, April 4, 2008 at 7:44pm
0.867 g/mol= x/ 20 ml x= 17.94 gYou made a math error here. I get 17.34 g
0.874 g/mol= x/ 150 mil x= 131.1 gThis is OK.
toluene 17.904 g x 1 m/ 92.14 g/ mol= .194 m This should be 17.34 g toluene. And that divided by 92.14 = 0.188 mols toluene. Then 0.188/kg solvent = 0.188/0.1311 = 1.434 which I would round to 1.43 for molality toluene.
benzee 131.1 g x 1m/78.1121 g/mol = 1.68 m
.194 m Toluene/ .1311 kg = 1.48 see above for correction.
For molarity of toluene, we have 0.188 mols/150 mL or 0.188/0.150 L = 1.25 mols/L = 1.25 M.
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To find the molarity (M) and molality (m) of the toluene in the solution, we can follow these steps:
1. Use the density of toluene, 0.867 g/mL, to determine the mass of toluene:
Mass of toluene = volume of toluene * density of toluene
Mass of toluene = 20.0 mL * 0.867 g/mL
Mass of toluene = 17.34 g (rounding to two decimal places)
2. Convert the mass of toluene to moles of toluene:
Moles of toluene = mass of toluene / molar mass of toluene
Molar mass of toluene = 92.14 g/mol
Moles of toluene = 17.34 g / 92.14 g/mol
Moles of toluene = 0.188 mol (rounding to three decimal places)
3. Use the density of benzene, 0.874 g/mL, to determine the mass of benzene:
Mass of benzene = volume of benzene * density of benzene
Mass of benzene = 150.0 mL * 0.874 g/mL
Mass of benzene = 131.1 g (rounding to one decimal place)
4. Find the molality of toluene:
Molality of toluene = moles of toluene / kg of solvent
Mass of benzene = 131.1 g
Kg of solvent = 131.1 g / 1000 g/kg
Kg of solvent = 0.1311 kg
Molality of toluene = 0.188 mol / 0.1311 kg
Molality of toluene = 1.434 (rounding to three decimal places)
5. Find the molarity of toluene:
Molarity of toluene = moles of toluene / volume of solution
Volume of solution = volume of toluene + volume of benzene
Volume of solution = 20.0 mL + 150.0 mL
Volume of solution = 170.0 mL = 0.170 L (converting mL to L)
Molarity of toluene = 0.188 mol / 0.170 L
Molarity of toluene = 1.106 M (rounding to three decimal places)
To find the molarity and molality of toluene in the solution, you need to follow these steps:
1. Determine the mass of toluene:
- The density of toluene (C6H5CH3) is given as 0.867 g/mL.
- The volume of toluene used is 20.0 mL.
- Multiply the volume (20.0 mL) by the density (0.867 g/mL) to find the mass of toluene: 20.0 mL * 0.867 g/mL = 17.34 g.
2. Convert mass to moles of toluene:
- The molar mass of toluene is 92.14 g/mol.
- Divide the mass of toluene (17.34 g) by its molar mass (92.14 g/mol) to get the number of moles of toluene: 17.34 g / 92.14 g/mol = 0.188 mol.
3. Calculate molality of toluene:
- The molality (m) is defined as the number of moles of solute (in this case, toluene) per kilogram of solvent.
- The mass of solvent (benzene) is given as 150.0 mL, which has a density of 0.874 g/mL.
- Convert the mass of solvent to kilograms: 150.0 mL * 0.874 g/mL = 131.1 g.
- Divide the number of moles of toluene (0.188 mol) by the mass of solvent in kg (131.1 g converted to kg, which is 0.1311 kg) to find the molality of toluene: 0.188 mol / 0.1311 kg = 1.434 mol/kg.
4. Calculate molarity of toluene:
- The molarity (M) of a solution is the number of moles of solute per liter of solution.
- Convert the volume of toluene (20.0 mL) to liters: 20.0 mL / 1000 mL/L = 0.0200 L.
- Divide the number of moles of toluene (0.188 mol) by the volume of solution in liters (0.0200 L) to find the molarity of toluene: 0.188 mol / 0.0200 L = 9.40 M.
Therefore, the molality of toluene is approximately 1.43 mol/kg, and the molarity of toluene is approximately 9.40 M.