[Wuffle]

Hi!

I would like to ask some post lab questions which I have troubles answering.
We did a lab where we put a liquid into a flask, secured foil on the top and got  a hole in the foil so the vapor could push out the air. Then, we heated the flask in boiling water until all the liquid had evaporated. We then let the flask cool and recorded the mass of the condensed vapor. Using this information, we found the molar mass of the liquid.

So , how would the molar mass change if

If the amount of unknown liquid added to the test tube was not enough to completely fill the tube with vapour.

and

If all of the unknown liquid did not evaporate.

For the first one , im guessing the molar mass with decrease as mass of the condensed liquid would be lower?

what about second one? if all of the unknown liquid did not evaporate, then the mass of the liquid would be higher?


we also determined the molar volume of a gas, where we pretty much got mg and hcl to react and we got equipment to measure pressure volume and temperatures when reaction accured and we were asked how would the following conditions change the calculated molar volume of hydrogen gas :

a)all of the magnesium did not react

b)Water vapour from the aqueous hcl was also present in the flask after the reaction

c)the calculated volume of the flask was lower than the actual volume available for the gas.

for  the first one, as there was lesser Mg reacting, the amount of moles of H2 is less, so the molar volume should be higher since molar volume =v/n, since n is lower , molar volume is higher.

for b I have no idea, maybe it didnt affect the molar volume at all?

for c I'm thinking since the molar volume=v/n , im guessing since v is lower, molar volume will become lower as well??


It's kinda difficult for me to explain what we really did in these experiments, I apologize for such bad description of experiments, could you guys help me?

that's what i assume, i'm probably wrong, could you please help me?

[gnahzmx]

I could not understand the experiment set 1 you described.
For the second set, I found a detailed experimental description online.
http://www.ar.cc.mn.us/chemistry/chem1061/Labs/Mg+HCl/Mg+HCl-vm.htm

I agree with for the answer in a and c. For b, I think you can get it using similar logic. what does the water vapor change in the measurement?