Flashcards in FINAL EXAM- The Mole Deck (14):
Atomic mass unit
A unit of mass that describes the mass of an atom or molecule; it is exactly 1/12 of the mass of a carbon-12 atom.
a particle of an ionic compound.
a particle of a covalent compound.
a particle of an element.
The SI base unit used to measure the amount of a substance whose nuber of particles is the same as the number of atoms of carbon in exactly 12 grams of carbon-12.
6.02 X 1023, the number of atoms or molecules in 1 mol.
The mass in grams of 1 mol of a substance (found on periodic table).
a chemical formula that shows the composition of a compound in terms of the relative numbers and kinds of atoms in the simplest ratio (simplest whole number ratio of atoms in a compound).
gives the actual number of atoms of each element in the compound
The percentage by mass of each element in a compound.
list and add
Determine empirical formulas
- How to recognize: will ask for the empirical formula
- How to solve:
- For each element, write the mass of the element/1 and multiply by 1 mol element/atomic mass and label them g element
- Take those numbers, divide each one by the smallest one out of all of them
- If numbers are in whole number ratios, use that as the subscripts in your formula, if not, multiply them to get the smallest whole number ratio and use that
- Problems like 13 and 15 give the percent compositions of each element but not the mass. In this case, use percent composition (percent, divide by 100, multiply by total mass of compound/denominator) to find the masses, then use those as you normally would
Determine molecular formulas
- How to recognize: will ask for molecular formula
- How to Solve:
- Follow the exact same steps from H to determine the empirical formula
- Use the empirical formula to find the mass of the empirical formula and see if it matches the mass of the compound
- To do this, take the mass of the compound and divide it by the mass you got
- Multiply the subscripts of each of the elements by that number to get the molecular formula
- If this number is one, you already have the molecular formula (empirical and molecular are the same in this case)