# Like this study set? Create a free account to save it.

### molecular mass

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

### formula mass

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

### 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

### 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

### 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?

Convert

56mg -->grams x 1000 56000

56000/mass-->56000/27.02

multiply by avogardo

56000/27.02 * 6.022 x 10²³

1.2 x 10²³

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

Hence

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.