an organic compound contains 32% carbon,4%hydrogen,64%oxygen .Find the molecular empirical formula .Molar mass is 75 .Find the molecular formula.
Answers
Explanation:
Answer: The empirical formula is C_2H_3O_3C
2
H
3
O
3
and molecular formula is C_4H_6O_6C
4
H
6
O
6
.
Solution : Given,
If percentage are given then we are taking total mass is 100 grams.
So, the mass of each element is equal to the percentage given.
Mass of C = 32 g
Mass of H = 4 g
Mass of O = (100-36)= 64 g
Step 1 : convert given masses into moles.
Moles of C =\frac{\text{ given mass of C}}{\text{ molar mass of C}}= \frac{32g}{12g/mole}=2.66moles
molar mass of C
given mass of C
=
12g/mole
32g
=2.66moles
Moles of H = \frac{\text{ given mass of H}}{\text{ molar mass of H}}= \frac{4g}{1g/mole}=4moles[/tex]
Moles of O = \frac{\text{ given mass of O}}{\text{ molar mass of O}}= \frac{64g}{16g/mole}=4mole
molar mass of O
given mass of O
=
16g/mole
64g
=4mole
Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.
For C = \frac{2.66}{2.66}=1
2.66
2.66
=1
For H = \frac{4}{2.66}=1.5
2.66
4
=1.5
For O= \frac{4}{2.66}=1.5
2.66
4
=1.5
The ratio of C : H : O= 1 :1.5 :1.5
Converting them into simple whole number ratio by multiplying by 2.
Hence the empirical formula is C_2H_3O_3C
2
H
3
O
3
The empirical weight of C_2H_3O_3C
2
H
3
O
3
= 2(12) + 3(1) +3(16)= 75g.
Molecular mass=2\times vapor density=2\times 75=150g2×vapordensity=2×75=150g
Now we have to calculate the molecular formula.
n=\frac{\text{Molecular weight of metal}}{\text{Equivalent of metal}}n=
Equivalent of metal
Molecular weight of metal
n=\frac{150g/mole}{75g/eq}=2n=
75g/eq
150g/mole
=2
Molecular formula is C_4H_6O_6C
4
H
6
O
6
hope it's helpful