What is the empirical formula for a compound that is 1.67g Ce and 4.54g I?
Convert to mols.
mols = grams/molar mass.
Then find the ratio of the mols to each other with the smallest number being 1.00. The easy way to do that is to divide the smaller mols by itself and divide the other number by the same small number. Round to the nearest whole number and that will be the empirical formula.
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To determine the empirical formula of a compound using percent composition or given mass quantities, follow these step-by-step instructions:
Step 1: Convert the given masses of each element to moles.
Given:
Mass of Ce = 1.67 g
Mass of I = 4.54 g
To convert grams to moles, use the molar mass of each element:
Molar mass of Ce = 140.116 g/mol
Molar mass of I = 126.90447 g/mol
Moles of Ce = mass of Ce / molar mass of Ce = 1.67 g / 140.116 g/mol = 0.0119 mol
Moles of I = mass of I / molar mass of I = 4.54 g / 126.90447 g/mol = 0.0357 mol
Step 2: Divide the moles of each element by the smallest number of moles (to get a whole number ratio).
Divide both moles of Ce and I by 0.0119 mol (the smallest number of moles):
Moles of Ce = 0.0119 mol / 0.0119 mol = 1
Moles of I = 0.0357 mol / 0.0119 mol = 3
Step 3: Write the empirical formula using the whole number ratios obtained in the previous step.
The empirical formula will be:
CeI3
Therefore, the empirical formula for the compound is CeI3, indicating that there is one cerium atom and three iodine atoms in each molecule of the compound.
To determine the empirical formula of a compound, you need to find the relative number of atoms of each element in the compound. This can be done by finding the moles of each element and then finding the simplest whole number ratio between them.
To find the moles of each element, you can use the molar mass of the elements. The atomic mass of Ce (cerium) is 140.12 g/mol, and the atomic mass of I (iodine) is 126.90 g/mol.
Moles of Ce = Mass of Ce / Molar mass of Ce
= 1.67 g / 140.12 g/mol
= 0.0119 mol (rounded to 4 decimal places)
Moles of I = Mass of I / Molar mass of I
= 4.54 g / 126.90 g/mol
= 0.0358 mol (rounded to 4 decimal places)
Now, divide the moles of each element by the smallest number of moles to find the mole ratio:
Moles of Ce / Moles of I = 0.0119 mol / 0.0119 mol (smallest number of moles)
= 1
Moles of I / Moles of I = 0.0358 mol / 0.0119 mol (smallest number of moles)
= 3
The mole ratio of Ce to I is 1:3. Therefore, the empirical formula for the compound is CeI3.