[ii] Calculate the mole fraction of methanol if the mass percent of methanol in water is 25%.
Answers
Explanation:
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Explanation:
Volume of methyl alcohol =4.6cm
3
Density of methyl alcohol =0.7952gcm
−3
⇒Density=
Volume
Mass
⇒0.7952=
4.6
Mass
⇒Mass=3.657g
∴ Mass of methyl alcohol =3.657g
(i) % by mass of methyl alcohol =
mass of methyl alcohol+mass of water
mass of methyl alcohol
×100=
3.657+25.2
3.657
×100=12.6%
(ii) Mole fraction of methyl alcohol and water-
Moles of methyl alcohol =
Molecular mass of methyl alcohol
Mass of methyl alcohol
Molecular mass of methyl alcohol (CH
3
OH)=12+4×1+16=32g
∴ Moles of methyl alcohol =
32
3.657
=0.114
Moles of water =
Molecular mass of water
Mass of water
=
18
25.6
=1.42
Total no. of moles = moles of methyl alcohol + moles of water =0.114+1.42=1.534
∴ Mole fraction of methyl alcohol =
total no. of moles
moles of methyl alcohol
=
1.534
0.114
=0.075
Mole fraction of water =
total no. of moles
moles of water
=
1.534
1.42
=0.925