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chemistry

In BHT Freezing Point Depression Lab:

The following errors occurred when the above experiment was carried out. How would each affect the calculated molecular mass of the solute (too high, too low, no effect)? Explain your answers.

The thermometer used actually read 1.4°C too high.

Some of the solvent was spilled before the solute was added.

Some of the solute was spilled after it was weighed and before it was added to the solvent.

Some of the solution was spilled after the solute and solvent were mixed but before the freezing point was determined.

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  1. Here are the three equations used to calculate the molar mass and I've labeled them eqn 1, 2 & 3. Remember that making the numerator of a fraction too large makes the result too large and making the numerator too small makes the result too small. Also, making the denominator of a fraction too large makes the result too small and making the denominator too small makes the result too large.
    equation 1. delta T = (Tfinal - Tinitial )= Kb*molality
    equation 2. moles solute = molality x kg solvent
    equation 3. molar mass solute = grams/moles.

    The following errors occurred when the above experiment was carried out. How would each affect the calculated molecular mass of the solute (too high, too low, no effect)? Explain your answers.

    The thermometer used actually read 1.4°C too high.
    See eqn 1. Tfinal will be 1.4 degrees too high and Tinitial will be 1.4 degrees to high but delta T will be the same so the calculated molar mass will be unchanged

    Some of the solvent was spilled before the solute was added.
    See eqn 2 first. You weigh the solvent but spill some before the solute is added; therefore, the weight of the solvent entered into the calculations is too much (too high) which makes moles from eqn 2 too high, which makes molar mass from eqn 3 too small.

    Some of the solute was spilled after it was weighed and before it was added to the solvent.
    I'll leave this one and the next one for you. Go through step by step.
    Some of the solution was spilled after the solute and solvent were mixed but before the freezing point was determined.
    Post your work if you get stuck or if you want someone to check your answers to the last two.

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  2. I made a typo in equation 1. I should have written
    delta T = (Tfinal-Tinital) = Kf*m but that doesn't change any of my answer or the logic.

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