Multiple Choice
An ethylene glycol solution contains 25.2 g of ethylene glycol (C2H6O2) in 99.5 mL of water. Determine the change in boiling point. Assume a density of 1.00 g/mL for water.
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13. Solutions
Boiling Point Elevation
Multiple Choice
Carbon dioxide is dissolved in 722 mL of benzene with a density of 1.59 g/mL. What mass of carbon dioxide would you add to make the boiling point of the solution 104.7ºC?
A
11 g
B
500 g
C
22.9 g
D
491 g
Verified step by step guidance1
First, determine the mass of benzene using its volume and density. Use the formula: mass = volume × density. Here, the volume is 722 mL and the density is 1.59 g/mL.
Next, calculate the molality of the solution needed to achieve the desired boiling point elevation. Use the formula for boiling point elevation: ΔT = i × K_b × m, where ΔT is the change in boiling point, i is the van't Hoff factor (which is 1 for non-electrolytes like CO₂), K_b is the ebullioscopic constant for benzene, and m is the molality.
Rearrange the boiling point elevation formula to solve for molality (m): m = ΔT / (i × K_b). Substitute the values for ΔT (104.7ºC - 80.1ºC, the normal boiling point of benzene), i, and K_b.
Once you have the molality, calculate the moles of CO₂ needed using the formula: moles = molality × mass of solvent (in kg). Convert the mass of benzene from grams to kilograms before using it in the calculation.
Finally, convert the moles of CO₂ to mass using the molar mass of CO₂ (approximately 44.01 g/mol). Use the formula: mass = moles × molar mass. This will give you the mass of CO₂ needed to achieve the desired boiling point.
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