QuestionII. Answer the following questions:
1. If the thermometer consistently displays a temperature of lower than the actual temperature throughout the experiment, what effect, (i.e., too high, too low, or no effect) would this have on the calculated molar mass of the unknown? Explain your answer.
Any error is the
2. If the freezing point of the solution had been incorrectly read as lower than its true freezing point and the freezing point of the pure solvent was correctly read, what effect (i.e., too high, too low, or no effect) would this have on the calculated molar mass of the unknown? Explain.
3. Calcium chloride, , is commonly used as road salt. If one mole of is dissolved in 1 kg of water, would the freezing point of the solution be greater than, less than, or the same as a solution prepared by dissolving one mole of table sugar (or sucrose), , in 1 kg of water? Explain.
Studdy Solution
STEP 1
1. The thermometer error affects the temperature readings consistently.
2. The freezing point depression formula is used to calculate molar mass.
3. The van 't Hoff factor (i) is relevant for solutions of electrolytes and non-electrolytes.
STEP 2
1. Analyze the effect of a consistent thermometer error on calculated molar mass.
2. Evaluate the impact of an incorrect freezing point reading on calculated molar mass.
3. Compare the freezing point depression effects of calcium chloride and sucrose solutions.
STEP 3
1.1. Understand the relationship between temperature readings and molar mass calculation: - The molar mass is calculated using the freezing point depression equation: where is the freezing point depression, is the van 't Hoff factor, is the cryoscopic constant, and is the molality. 1.2. Determine the effect of a consistent thermometer error: - If the thermometer reads lower, the measured freezing point depression will be larger than the true value. - This will result in a calculated molar mass that is too low because the apparent is larger.
STEP 4
2.1. Analyze the impact of a error in freezing point reading: - The error affects the calculation, making it larger than it should be. - This leads to a calculated molar mass that is too low, as the apparent is exaggerated.
STEP 5
3.1. Compare the effects of dissolving and sucrose in water:
- dissociates into three ions ( and two ), so .
- Sucrose does not dissociate, so .
- The freezing point depression is greater for because the van 't Hoff factor is larger.
- Therefore, the freezing point of the solution is lower than that of the sucrose solution.
Answers:
1. The calculated molar mass would be too low due to the consistent thermometer error.
2. The calculated molar mass would be too low due to the incorrect freezing point reading.
3. The freezing point of the solution would be less than that of the sucrose solution.
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