How would you find the molecular formula for a compound with molar mass 180 amu, that is composed of 40% carbon 6,67% hydrogen 53.3 oxygen?

Question

How would you find the molecular formula for a compound with molar mass 180 amu, that is composed of  40% carbon 6,67% hydrogen 53.3 oxygen?

Wyatt Adkins · Accepted Answer

#C_6H_12O_6#

We consider a compound of 100 g.

Each element's atomic mass divides the elemental composition:

#C: (40*cancelg)/(12.011*cancelg*mol^-1)# #=# #3.33*mol#.

#H: (6.67*cancelg)/(1.00794*cancelg*mol^-1)# #=# #6,62*mol#.

#O: (53.3*cancelg)/(15.99*cancelg*mol^-1)# #=# #3.33*mol#.

So the empirical formula is #CH_2O#, after we divide thru by the lowest quotient.

We can now conclude that the molecular formula is always the empirical formula multiplied by a whole number:

i.e. #(12.011+2xx1.0074+15.99)_n*g*mol^-1# #=# #180*g*mol^-1.#

Thus #n# #=# #6#, and the molecular formula is #C_6H_12O_6#.

Luna Chen · Answer

undefined In order to find the molecular formula for the compound, you must first find the empirical formula. Once the empirical formula has been determined, you can find the molecular formula using the given molar mass. 1. Calculate the number of moles of each element: - Carbon: (40% of 180 amu) / (12.01 g/mol) - Hydrogen: (6.67% of 180 amu) / (1.008 g/mol) - Oxygen: (53.3% of 180 amu) / (16.00 g/mol)
2. Determine the mole ratio of the elements by dividing the number of moles of each element by the smallest number of moles obtained. 3. Round the mole ratios to the nearest whole number to obtain the empirical formula. 4. Calculate the molar mass of the empirical formula. 5. Divide the given molar mass (180 amu) by the molar mass of the empirical formula to find the ratio. 6. Multiply the subscripts in the empirical formula by