Question

What would happen to the results in this experiment if the student read the barometric pressure as 713 mm Hg rather than its true value of 743 mm Hg?

a) The moles of the vapor would be too small, thus the calculated molar mass would be too large.

b) The moles of the vapor would be too small, thus the calculated molar mass would be too small.

c) The moles of the vapor would be too large, thus the calculated molar mass would be too large.

3. What will happen to the results in this experiment if the flask was removed from the bath before the vapor had reached the temperature of the boiling water and all the liquids had vaporized?

a) The temperature of the vapor would be too low; observed mass of vapor will be too high; thus the molar mass would be too large.

b) The temperature of the vapor would be too low; observed mass of vapor will be too low; thus the molar mass would be too large.

c) The temperature of the vapor would be too high; observed mass of vapor will be too high; thus the molar mass would be too large.

Answer 1

2. According to ideal gas law, PV = nRT. Hence, if P is lesser than what it is, then n would also be lesser.

n= m/M where M is the molar mass. If n is less, then M would be more than what it should be.

Answer: a) the moles of vapor would be too small, thus the calculated molar mass would be too large.

3. The temperature would be too low. Hence, n would be high. This implies , the observed mass would be high

Answer- a) the temperature of the vapor would be too low; observed mass of vapor would be too high; thus the molar mass would be too large.