Question

thanx

Answer 1

1. Calculate the number of moles of hydrogen gas collected for each trial.
PV=nRT => n=PV/RT
I dont know exactly the conditions of your experiments but I will assume that from the table you can use the volume of H2 collected as your V, (convert to L). Then you barometric pressure as your P (convert to atm) and yout temperature in Kelvin as T.

2. Calculate the number of grams of Aluminum for each trial. Consider the balanced equation in the calculations.
you dont give the balanced equation I will assume that you are doing a reaction of the Al in the can dissolved with HCl acid and producing H2
2Al(s)+ 6HCl(l) -> AlCl3(aq) + 3H2(g)
you will have a 2Al moles /3H2 moles stoichiometric relationship. Whit this you can calculate how many moles of Al have reacted. Then the mass multiply the moles by the atomic mass of Al.

Answer 2

3. Calculate the %purity of aluminum for each trial.
the Al mass calculated in the step 2 divided by the initial mass of the sample in g times 100.

4. Calculate the average value of the purity of the sample.
average of the 3 values calculated in step 3

5. Assuming that thee usual purity value for the aluminum content using this procedure is 95.2% , calculate the relative error(%) of your average.

the average value from step 3 multiply by 100 divided by 95.2

Answer 3

Hi Cuanchi,

For #1, I put:

\[\frac{ (755 atm)(0.02L )}{(0.08206L)(atm)(296.15K)}=0.62 mol H _{2}\]

is this right?

Answer 4

Also for part 2 is this right?

\[0.62 mol H _{2} (\frac{ 2mol Al }{3mol H _{2} } )(\frac{ 26.98g Al }{ 1 mol Al } = 11 g Al\]

Answer 5

no!
For #1, to calculate the number of moles
The pressure that you have to use is the atmospheric pressure minus the H2O pressure. That is your H2 pressure.
Then you have to convert the pressure from mmHg to atmospheres (1atm=760mmHg)

Answer 6

the second part is fine just change the moles of H2