3.10 Determining a Chemical Formula from Experimental Data Flashcards
We can determine a chemical formula, but it is an _______ _______(not a molecular formula). To get a _______ _______, we need additional information, such as the molar mass of the compound.
We can determine a chemical formula, but it is an empirical formula (not a molecular formula). To get a molecular formula, we need additional information, such as the molar mass of the compound.
How do we determine an empirical formula from these data? We know that an empirical formula represents a ratio of atoms or a ratio of moles of atoms, not a ratio of ______
How do we determine an empirical formula from these data? We know that an empirical formula represents a ratio of atoms or a ratio of moles of atoms, not a ratio of masses
the first thing we must do is convert our data from mass (in _____) to amount (in ____).
the first thing we must do is convert our data from mass (in grams) to amount (in moles).
How many moles of each element are present in the sample? To convert to moles, we _____ each mass by the _______ _______ of that element
How many moles of each element are present in the sample? To convert to moles, we divide each mass by the molar mass of that element
rom these data, we know there are 0.849 mol H for every 0.429 mol O. We can now write a _______ _______ for water:
rom these data, we know there are 0.849 mol H for every 0.429 mol O. We can now write a pseudo formula for water:
Our empirical formula for water, which also happens to be the _______ _______ , is H2O .
Our empirical formula for water, which also happens to be the molecular formula, is H2O .
We can find the _______ _______ of a compound from the _______ _______ if we also know the molar mass of the compound.
We can find the molecular formula of a compound from the empirical formula if we also know the molar mass of the compound.
that the molecular formula is always a _______-_______ multiple of the _______ _______ :
_______ _______ = _______ _______ * n, where n = 1, 2, 3,…
that the molecular formula is always a whole-number multiple of the empirical formula:
Molecular formula = empirical formula * n, where n = 1, 2, 3,…
Suppose we want to find the molecular formula for fructose (a sugar found in fruit) from its empirical formula, CH2O, and its molar mass, 180.2 g/mol. We know that the molecular formula is a whole-number multiple of CH2O :
Molecular formula = _____ * n = ______
Molecular formula = (CH2O) * n = CnH2nOn
We also know that the molar mass is a whole-number multiple of the empirical formula molar mass , the sum of the masses of all the atoms in the empirical formula.
Molar mass = _______ _______ molar mass * n
We also know that the molar mass is a whole-number multiple of the empirical formula molar mass , the sum of the masses of all the atoms in the empirical formula.
Molar mass = empirical formula molar mass * n
For a particular compound, the value of n in both cases is the same. Therefore, wecan find n by calculating the ____ of the molar mass to the _______ _______ molarmass:
n = _______ _______ / _______ _______ _______ _______
For a particular compound, the value of n in both cases is the same. Therefore, wecan find n by calculating the ratio of the molar mass to the empirical formula molarmass:
n = molar mass/ empirical formula molar mass
Another common (and related) way to obtain empirical formulas for unknown compounds, especially those containing carbon and hydrogen, is _______ _______.
Another common (and related) way to obtain empirical formulas for unknown compounds, especially those containing carbon and hydrogen, is combustion analysis.
In combustion analysis, the unknown compound undergoes combustion (or burning) in the presence of _______ _______,
In combustion analysis, the unknown compound undergoes combustion (or burning) in the presence of pure oxygen,
