Chapter 6 Flashcards
What is a mole?
It is a way to count atoms or molecules.
How many atoms or molecules in a mole?
6.022 X 1023
What is Avogadro’s number?
6.022 X 1023
What is Avogadro’s number used to do?
convert between number ot atoms, molecules, or formula units.
What is the molar mass of an element?
It is the mass of one mole of atoms of the element.
What can the molar mass be used to do?
Used to convert the mass of an element to the number of moles.
How is the mass of an element converted to the number of atoms.
Example: 24.02 g of carbon with 12.01 amu
24.02 g of C x ( 6.022 x 1023 atoms of C / 12.01 g of C) = 2 moles or 2.0 x 6.022x 1023 molecules
What is molar mass equivalent to?
Formula mass in atomic mass units. For example for carbon: 12.01 amu = 12.01 grams/mole
What is the molar mass of nitrogen dioxide (NO2) if N = 14.01 amu and O = 16.00 amu?
1 x 14.01 amu + 2 x 16.00 amu = 46.01 amu = 46.01 grams or NO2 per mole
If there is 92.02 grams of NO2, how many moles are there is N = 14.01 amu and O = 16.00 amu?
For NO2, molecular mass is 1 x 14.01 amu + 2 x 16.00 amu = 46.01 amu = 46.01 grams/mole.
So (92.02 grams) / (46.01 grams/mole) = 2 moles
If there is 6.005 g of carbon (C = 12.01 amu), how many molecules are there?
- 005 grams / (12.01 grams/mole) = 0.5 moles
- 5 moles * (6.022 x 1023 molecules/mole) = 3.011 x 1023 molecules
What is the empirical formula?
Smallest whole number ratio of each type of atom in molcule.
What is the molecular formula?
The actual number of each atom in a molecule.
What is the molar mass?
It is a conversion factor between the mass (in grams) and the moles. For example, carbon is 12.01 grams/mole.
What is the mass percent?
It is the element’s percent of the total mass of the compound.
True or False: mass percent can be used to determine the empirical formula if the elements are known
True. With elements’ molar mass, number of moles can be determined. Once moles are known then empirical formula is just lowest whole number ratio.
How many atoms are there in 0.5 moles?
0.5 x 6.022 x 1023
If carbon is 12.01 grams/mole, how many moles are there in 24.02 grams
24.02 grams / (12.01 grams/mole) = 2 moles
If helium is 4.00 grams/mole, how much does 6.022 x 1024 atoms weigh?
6.022 x 1024 atoms / (6.022 x 1023 atoms/mole) x 4.00 grams/mole = 400 grams
What is mole mass of bicarbonate (HCO3) if H = 1.01 g/mole, C = 12.01 g/mole, O = 16.00 g/mole
1 x 1.01 g/mole + 1 x 12.01 g/mole + 3 x 16.00 g/mole = 61.02 g/mole
What is the empirical formula of the compound which contains 2.02 g of hydrogen, 48.04 g of carbon, and 32.00 g of oxygen. H = 1.01 g/mole, C = 12.01 g/mole, O = 16.00 g/mole.
H: 2.02 g / 1.01 g/mole = 2 moles
C: 48.04 g / 12.01 g/mole = 4 moles
O: 32.00 g / 16.00 g/mole = 2moles
Formula: H2C4O2
Empirical Formula: HC2O
What is mass percent of oxygen in acetic acid (C2H4O2) if H = 1.01 g/mole, C = 12.01 g/mole, O = 16.00 g/mole
Molar mass of C2H4O2 is 60.06 g/mole and O2 is 32.00 g/mole. Mass percent of O2 is 32.00/60.06 = 0.5328 = 53.28%