Question

2. Combustion of 1.000 g of the compound that has carbon, oxygen and hydrogen yields 1.734 g CO, and 0.803 g H,O. In another experiment, 0.1067 g of the compound was dissolved in 23.6 g of water. This solution had a freezing point of -0.0914°C. What is the molecular formula of the compound?

Answer 1

Solution:-
1.
Mass of CO2 is 1.734 g
We know the molar mass of CO2 is 44g/mole
So we 0.039 moles of CO2.
There is 1mole C in CO2
Mass of C is 0.039x12=0.468 g
2.
We have H2O=0.803 g
Molar mass of water is 18g/mol
So we have 0.0447 moles of H2O.
But there are 2 moles oh hydrogen in 1 mole of H2O that is 0.0894 moles of H
Mass =0.0894 x 1=0.089g
So molar ratio is C:H is
0.039:0.0894
Mass of C+H is
0.557 g
Divide by smallest moles 0.039 will get
Molar ratio C:H
1.000: 2.28
Multiply by 3 to get whole number 3.000:6.84
So molecular formula is C3H7