Chemistry chapter 3

24 terms by joestang22 

Create a new folder

Advertisement Upgrade to remove ads

molecular mass

sum of the masses of the atoms making up the molecule (units amu) (molecular compounds only!)

Molecular mass H₂O

2+15.9994= 18

Molecular mass C₂H₄O₂

122+4+162= 24+4+32=60

formula mass

is the sum of atomic masses of all atoms in a formula unit of any compound, molecular or ionic (units amu)

Formula Mass NaCl




Define mole

substance is the quantity of a given substance that contains as many molecules or formula units as the number of atoms in exactly 12g of C-12.
Like 12 eggs in a dozen

Avogadro's Number

6.022 x 1023 molecules) is the numerical value assigned to the unit, 1 mole

Calculate mass with moles

Formula mass/6.02 x 10²³

How many Li₂SO₄ units are in 3 moles of Li₂SO₄?

7+32+16*4= 103
3moles x 6.02 x 10²³ x 1/1= 1.81 x 10²⁴

How many Li atoms are in 3 moles of Li₂SO₄?

3 moles x 6.02 x 10²³ x 2/1= 3.61 x 10²⁴

How many S atoms in 3 moles of Li₂SO₄?

3 moles x 6.02 x 10²³ x 1/1= 1.81 x 10²⁴

How many O atoms in 3 moles of Li₂SO₄?

3 moles x 6.02 x 10²³ x 4/1= 7.22 x 10²⁴

Molar Mass

mass of one mole of that substance
mass/avogadros #

What is mass in grams of Ca?

40.1 g/mol CA divided by /6.02 x 10²³= 6.66 x 10⁻²³

moles to grams


Mole calculations: consider ethanol with a molar mass of 46.1g/mol. Prepare acetic acid from 10.0 g of ethanol

10.0g x 1/ 46.1 = .217g/mol
grams divided by mass
grams to moles

Analysis of a solution shows it contains 0.909 mol of H2O2 in 1.00L of solution. What is the mass of hydrogen peroxide in this volume of solution?
molar mass of H2O2 is 34.02 g/mol

.909 mol * 34.02 g H₂O₂/1 ml H₂O₂= 30.92g
mole multiplied by mass
moles to grams

HCN is a volatile colorless liquid. The compound is highly poisonous . How many molecules are there in 56mg HCN, the average toxic does?

56mg -->grams x 1000 56000
multiply by avogardo
56000/27.02 * 6.022 x 10²³
1.2 x 10²³

Percent Composition

Mass % A = mass A in the whole X 100%
whole mass

The molecular mass of NH4NO3 = 80.05; its molar mass = 80.05g/mol.

N= 28.02/ total
28.02/80.05= .35 x 100%= 35%

How many grams of nitrogen are there in a fertilizer containing 48.5g of NH4NO3?

NH4NO3 is 35.0% N
(Fraction N = 0.350
48.5 x .35= 16.975= 17.0 g

Empirical Formula

Determined from data about percent composition, tells only the smallest whole number ratio of atoms in a compound.

Molecular Formula

n= molecular mass/empirical formula mass
C₂H₄O= 44amu
divide by actual mass, 44 amu = 1

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again


Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set