A flask was weighed and filled with C2H6 gas to a fixed temperature and pressure. The mass of ethane in the flask was found to be 1.10 grams. The same flask was flushed and filled with a different and unknown gas, confined under the same conditions. The mass of this gas was found to be 4.70 grams. Calculate the molar mass of the unknown gas to two significant figures. Enter your answer in scientific notation. For example: 3.6E2
need for test review..thnx
2007-03-23 19:20:52 · 3 answers · asked by aks s 1 in Science & Mathematics ➔ Chemistry
Take both gases as idel gases, then
P*V=n*R*T, gives idel gas equation.
Since pressure temperature and volume of both gases are same, no of moles of gas will be same for both gases
Hence n(C2H6)=n(unknown gas)
now n(C2H6)=mass of ethane/molecular mass of ethane
=1.1/(2*12.01+6*1.00794)
=1.1/30.06764
=0.03658 moles
Now n(unknown gas)=0.03658 moles
mass of unknown gas=4.7 gms
there fore molecular mass of unknown gas
=mass/ no of moles
=4.7/0.03658
=128.49 grams/mole
=1.28E2 gm/mol
2007-03-23 22:14:26 · answer #1 · answered by be_a_wave 2 · 0⤊ 0⤋
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2016-10-20 08:10:29 · answer #2 · answered by ? 4 · 0⤊ 0⤋
molar mass for C2H6 =6*1+2*12=30 gram/mole
the number of moles for C2H6=mass/molar mass=1.1/30=0.03 mole
the number of moles for the unknown gas=number of moles for C2H6*number of moles for the unknown gas=0.03*mass/molar mass=0.03*4.7/4.7=0.03
the answer is 0.03
2007-03-23 19:41:46 · answer #3 · answered by qute boy 1 · 0⤊ 0⤋