a compound is found to be 94.1% o and 5.90% h. its molecular mass is 34.0. what is its molecular formula
A. H3O2
B. OH
C. H2O
D. H2O2
I think D
You didn't show your work so I can't comment on that; however, the answer is right. I note, with some amusement, that D is the ONLY answer with a molar mass of 34. But that isn't the way to work the problem.
To determine the molecular formula of the compound, we need to calculate the empirical formula first. The empirical formula represents the simplest ratio of elements present in the compound.
To find the empirical formula, we first convert the percentages to grams. Let's assume we have 100 grams of the compound:
Oxygen (O) = 94.1 grams
Hydrogen (H) = 5.90 grams
Next, we need to calculate the number of moles for each element. To do this, we divide the mass of each element by its molar mass:
Oxygen (O):
Number of moles = Mass / Molar mass = 94.1 g / 16.00 g/mol = 5.88 moles
Hydrogen (H):
Number of moles = Mass / Molar mass = 5.90 g / 1.01 g/mol = 5.84 moles
Now, we need to find the simplest whole-number ratio of moles between the elements. We divide both mole values by their smallest common value, which is 5.84 in this case:
Oxygen (O):
5.88 moles / 5.84 = 1.005
Hydrogen (H):
5.84 moles / 5.84 = 1
The ratio results in approximately H1O1 or H2O, indicating that for every hydrogen atom, there is one oxygen atom. Therefore, the empirical formula is H2O.
Next, we compare the empirical molar mass of H2O to the given molecular mass of 34.0. If the molecular mass is consistent with the empirical molar mass, then the empirical formula is also the molecular formula. The empirical molar mass of H2O is:
(H = 1.01 g/mol) + (O = 16.00 g/mol) = 17.01 g/mol
Since the empirical molar mass of H2O (17.01 g/mol) does not match the given molecular mass (34.0), we need to multiply the empirical formula by 2 to get the molecular formula.
H2O * 2 = H4O2
So, the correct answer is A. H4O2