Question

An unidentified covalent molecular compound contains only carbon, hydrogen, and oxygen. When 7.40 mg of this compound is burned, 17.80 mg of CO2 and 2.08 mg of H2O are produced.
The freezing point of camphor is lowered by 26.4°C when 3.044 g of the compound is dissolved in 18.00 g of camphor (Kf = 40.0°C kg/mol).

What is the molecular formula of the unidentified compound?

Choose appropriate coefficients in the molecular formula below.
C H O

Answer 1

The molecular formular shows all the atoms in the compound. The molecular formula of the compound is C15H10O5.

What is molecular formula?

The molecular formula is the formula of the compound that shows the total number of atoms in a compound.

We know that;

ΔT = K m i

ΔT = 26.4°C

K = 40.0°C kg/mol

m = ?

i = 1

26.4°C = 40.0°C kg/mol * m * 1

m = 26.4°C/40.0°C kg/mol  = 0.66 m

We know that

m = mass/molar mass ÷ mass of solvent(in Kg)

Let the molar mass be MM

m = 3.044 g/MM ÷ (18 * 10^-3 Kg)

0.66 m =  3.044 g/0.018MM

0.66 m  * 0.018MM =  3.044 g

MM = 3.044 g/0.66 m  * 0.018

MM = 256 g/mol

Now;

Mass of C =  17.80 * 10^-3/44 * 12 = 0.00485 g

Moles of C = 0.00485 g/12 g/mol = 0.0004 moles

Mass of H = 2.08 * 10^-3/18  * 2 = 0.0002 g

Moles of H =  0.0002 g/1 g/mol = 0.0002 moles

Mass of O = [7.40 * 10^-3 - (0.00485 + 0.0002)] = 0.00235 g

Moles of O = 0.00235 g/16 g/mol = 0.000147 moles

Divide through by the lowest number of moles;

C - 0.0004/0.000147  H - 0.0002/0.000147  O - 0.000147 /0.000147

C - 3   H  -  2  O -  1

The empirical formula is C3H2O

So;

[3(12) + 2(1) + 1(16)]n = 256

[36 + 2 + 16]n = 256

n = 5

Molecular formula = C15H10O5

Learn more about molecular formula: brainly.com/question/14425592?