Volume of cyclohexane (mL) 20.69 mL Mass of cyclohexane (g) ??? g Freezing point
ID: 574873 • Letter: V
Question
Volume of cyclohexane (mL)
20.69 mL
Mass of cyclohexane (g)
???
g
Freezing point of pure cyclohexane (°C)
5.3 °C
Trial 1
Trial 2
Trial 3
Mass of weighing dish and sample (g)
2.8987 g
2.8036 g
2.6543 g
Mass of weighing dish (g)
2.5895 g
2.5994 g
2.5469 g
Mass of sample (g)
?? g
?? g
?? g
Total mass of sample (g)
??g
?? g
?? g
Freezing point of solution (average, °C)
4.1 °C
3.3 °C
2.9 °C
Freezing point depression (°C)
??°C
??°C
?? °C
Molality of solution (m)
?? m
?? m
?? m
Moles of sample in solution (moles)
?? moles
?? moles
?? moles
Molecular weight of sample (g/mol)
???x 10^??g/mol
??? x 10^??g/mol
??? x 10^??g/mol
Average molecular weight of sample (g/mol)
???x 10^?? g/mol
I AM HAVING EXTREME DIFFICULTY ANDYBIDY WHO CAN HELP I WOULD GREATLY APPRECIATE IT i NEED HELP AND IN THE LAST ONES, I NEED THE AVERAGE MOLECULAR WEIGHT OF SAMPLE IN A FORMAT LIKE THIS (8.0*10^5 G/MOL) SOMETHING LIKE THAT. I NEED HELP WITH THE CALCULATIONS IF YOU CAN SHOW WORK FOR EVEN ONE OF THE TRIALS i WILL GREATLY APPRECIATE IT
Volume of cyclohexane (mL)
20.69 mL
Mass of cyclohexane (g)
???
g
Freezing point of pure cyclohexane (°C)
5.3 °C
Trial 1
Trial 2
Trial 3
Mass of weighing dish and sample (g)
2.8987 g
2.8036 g
2.6543 g
Mass of weighing dish (g)
2.5895 g
2.5994 g
2.5469 g
Mass of sample (g)
?? g
?? g
?? g
Total mass of sample (g)
??g
?? g
?? g
Freezing point of solution (average, °C)
4.1 °C
3.3 °C
2.9 °C
Freezing point depression (°C)
??°C
??°C
?? °C
Molality of solution (m)
?? m
?? m
?? m
Moles of sample in solution (moles)
?? moles
?? moles
?? moles
Molecular weight of sample (g/mol)
???x 10^??g/mol
??? x 10^??g/mol
??? x 10^??g/mol
Average molecular weight of sample (g/mol)
???x 10^?? g/mol
I AM HAVING EXTREME DIFFICULTY ANDYBIDY WHO CAN HELP I WOULD GREATLY APPRECIATE IT i NEED HELP AND IN THE LAST ONES, I NEED THE AVERAGE MOLECULAR WEIGHT OF SAMPLE IN A FORMAT LIKE THIS (8.0*10^5 G/MOL) SOMETHING LIKE THAT. I NEED HELP WITH THE CALCULATIONS IF YOU CAN SHOW WORK FOR EVEN ONE OF THE TRIALS i WILL GREATLY APPRECIATE IT
Explanation / Answer
volume of cyclohexane = 20.69 ml
density of cyclohexane = 0.779 g/ml
Mass of cyclohexane = volume * density = 20.69*0.779 = 16.12 g = 0.01612 kg
For trial 1:
Mass of sample = (mass of weighing dish and sample)-(mass of weighing dish)
mass of sample = 2.8987-2.5895 = 0.3092 g
Total mass of sample = mass of sample+mass of cyclohexane = 0.3092+16.12 = 16.4292 g
Freezing point depression = freezing point of pure cyclohexane - freezing point of solution = 5.3-4.1 = 1.2 oC
molality of solution = freezing point depression/cryoscopic constant of cyclohexane = 1.2/20.0 = 0.06 m
moles of sample in solution:
molality = moles of solute/weight of solvent
moles of sample = molality*weight of solvent = 0.06*0.01612 = 9.67*10-4 mol
molecular weight of sample = mass of sample/moles of sample = 0.3092/9.67*10-4 = 319.69 g/mol = 3.20*102 g/mol
For trial 2:
Mass of sample = (mass of weighing dish and sample)-(mass of weighing dish)
mass of sample = 2.8036-2.5994 = 0.2042 g
Total mass of sample = mass of sample+mass of cyclohexane = 0.2042+16.12 = 16.3242 g
Freezing point depression = freezing point of pure cyclohexane - freezing point of solution = 5.3-3.3 = 2.0 oC
molality of solution = freezing point depression/cryoscopic constant of cyclohexane = 2.0/20.0 = 0.10 m
moles of sample in solution:
molality = moles of solute/weight of solvent
moles of sample = molality*weight of solvent = 0.10*0.01612 = 1.612*10-3 mol
molecular weight of sample = mass of sample/moles of sample = 0.2042/1.612*10-3 = 126.67 g/mol = 1.27*102 g/mol
For trial 3:
Mass of sample = (mass of weighing dish and sample)-(mass of weighing dish)
mass of sample = 2.6543-2.5469 = 0.1074 g
Total mass of sample = mass of sample+mass of cyclohexane = 0.1074+16.12 = 16.2274 g
Freezing point depression = freezing point of pure cyclohexane - freezing point of solution = 5.3-2.9 = 2.4 oC
molality of solution = freezing point depression/cryoscopic constant of cyclohexane = 2.4/20.0 = 0.12 m
moles of sample in solution:
molality = moles of solute/weight of solvent
moles of sample = molality*weight of solvent = 0.12*0.01612 = 1.934*10-3 mol
molecular weight of sample = mass of sample/moles of sample = 0.1074/1.934*10-3 = 55.52 g/mol
Average molecular weight of sample = (trial 1+ trial 2 + trial 3)/3
= (319.69+126.67+55.52)/3 = 167.30 g/mol = 1.67*102 g/mol
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.