1) If the barometer reading is recorded to be higher than the actual value. What

Question

1) If the barometer reading is recorded to be higher than the actual value. What effect does this error have on the reported value of the molar mass of the compound? Briefly explain (Too High, Too low, Unchanged)

2) If the water bath only reached a temperature of 94.9C but your still used the value of 100C in the calculation what effect would this error have on the reported value for the molar mass of the compound? Briefly explain (Too High, Too low, Unchanged)

3) A 250 mL Erlenmeyer flask has a measured volume of 287mL. The experiment is performed with a this flask but the volume of 250 mL is mistakenly used in the molar mass calculation. What effect does this error have on the reported value? Briefly explain (Too High, Too low, Unchanged)

4) When performing this experiment if your mistakenly added 6 mL of volatile liquid instead of 4 mL at the start. What effect would this have on the calculated value of the molar mass or the compound? Briefly explain (Too High, Too low, Unchanged)

Explanation / Answer

1) If the barometer reading is recorded to be higher than the actual value.
What effect does this error have on the reported value of the molar mass of the compound?
Briefly explain (Too High, Too low, Unchanged)

Actual Molar mass, MW = w/n = w*R*T/(P*V)
MWreported = w*R*T/(Preported*V)
reported pressure, Preported > P
So 1/Preported < 1/P
w*R*T/(Preported*V) < w*R*T/(P*V)
MWreported < MW
Reported molar mass, MWreported will be lower than actual molar mass, MW..

2) If the water bath only reached a temperature of 94.9C but your still used the value of 100C in the calculation
what effect would this error have on the reported value for the molar mass of the compound?
Briefly explain (Too High, Too low, Unchanged)

reported temperature, Treported = 100 C
actual temperature, T = 94.9 C
Treported > T
w*R*Treported/(P*V) > w*R*T/(P*V)
MWreported > MW
Reported molar mass, MWreported will be higher than actual molar mass, MW..

3) A 250 mL Erlenmeyer flask has a measured volume of 287mL. The experiment is performed with a this flask
but the volume of 250 mL is mistakenly used in the molar mass calculation.
What effect does this error have on the reported value? Briefly explain (Too High, Too low, Unchanged)

reported volume, Vreported = 250 ml
actual   volume, V = 287 ml
Vreported < V
1/Vreported > 1/V
w*R*T/(P*Vreported) > w*R*T/(P*V)
MWreported > MW
Reported molar mass, MWreported will be higher than actual molar mass, MW.

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