DOC

# CHEMISTRY-CP

By Leonard Henderson,2014-01-28 23:55
9 views 0
CHEMISTRY-CPCP

CHEMISTRY-CP

CHAPTER 10: THE MOLE

TEXTBOOK PAGES 310-345

OBJECTIVES:

Define mole and describe its importance

Define atomic mass, formula mass and molar mass

Calculate formula mass and molar mass

Convert among the number of particles, mole and mass of a substance

Define molar volume

Convert between molar volume and moles

Do multistep conversion problems

Define and calculate percent composition

Define and calculate molecular formulas

MOLES

× 22.4 L ? 22.4 L × molar mass

?molar mass

23? (6.02 x 10) 23× (6.02 x 10)

Atoms, Mass (grams) Volume (Liters)

Molecules or

Formula Units

Chemistry-CP The “mole” is a Chapter 10-The Mole counting unit just like a 10-1 Chemical Measurements “dozen” is a

counting unit Mole:

for 12.

o Establishes a relationship between:

o Sometimes referred to as:

Because:

When the substance is an element

1 mole =

When the substance is a molecular compound or diatomic element

1 mole =

When the substance is an ionic compound

1 mole =

Review of atomic mass The mass in grams of 1 mole of an element is numerically equal to the 1) The mass of an atom ___________________________ of that element. relative to the mass assigned to carbon-12 Formula Mass: 2) Found on the periodic table Units = 3) Expressed in amustandard unit used to describe the mass of an atom Molar Mass: 4) Round to 2 decimals Units =

Molar Mass =

Examples:

a) Find the formula mass of water.

b) Find the formula mass of acetic acid, HCHO. 232

c) Find the formula mass of baking soda, NaHCO. 3

d) What is the molar mass of glucose, CHO? 6126

e) Find the molar mass of carbon monoxide.

f) Find the molar mass of magnesium hydroxide.

g) Find the molar mass of hydrochloric acid.

10-2 Molar Conversions

Mole ; Mass

o 1 mole = ___________________________________________

The conversion factors are:

Moles ; Particles

o 1 mole = ___________________________________________

The conversion factors are:

Moles ; Volume (for gases)

o Molar Volume:

Standard Temperature and Pressure (STP):

1 mole = ___________________________________________

o The conversion factors are:

Review: To Convert Between Units

1. Write down the measurement given in the question (number and unit)

2. Times a line.

3. Insert the correct conversion factor so that

a) units cancel

b) the unit you are converting to is on the top of the conversion factor

4. Check your answer to make sure the final unit is the desired unit. If not, continue with

the conversions by…

a) times a line again, and insert the appropriate conversion factor

Molar Conversion Factors: 23 atoms, molecules or formula units 1 mole = 6.02 × 10 1 mole = molar mass (grams) 31 mole = 22.4 L (dm)

Review of sig figs: Examples (1-step conversions) The answer to a a) How many molecules are in 2 moles of water? multiplication/division

problem should contain the same # of sig figs as the measurement with the lowest # of sig figs.

b) You have an 11.2 g sample of table salt. How many moles of salt do you have?

c) A student fills a 5.0 L flask with carbon dioxide gas at standard temperature and pressure.

How many moles of gas are in the flask?

d) How many moles is equivalent to 16.3 grams of lithium bromide?

23e) A piece of marble contains 8.74 × 10 formula units of calcium carbonate. How many

moles of calcium carbonate is that?

Molar Conversion Factors: 23 atoms, molecules or formula units 1 mole = 6.02 × 10 1 mole = molar mass (grams) 31 mole = 22.4 L (dm)

More Examples (1-step conversions)

f) How many grams are present in a 2.50 mole sample of sodium carbonate?

g) Determine the number of atoms in 0.36 mol of aluminum.

h) How many liters of gas are present in 7.2 moles of chlorine gas?

Examples (Multi-step conversions) 22a) How many grams of calcium are present in 7.2 × 10 atoms of calcium?

b) You need 250 grams of table sugar, or sucrose (CHO), to bake a cake. How many 122211

sucrose molecules will be in the cake?

c) How many formula units of magnesium chloride are in 1.8 grams of magnesium chloride?

24d) If you burned 4.0 × 10 molecules of natural gas, or methane (CH), during a laboratory 4

experiment at STP, how many liters of methane did you burn?

10-3 Empirical and Molecular Formulas

Percent Composition:

o Purpose of Calculating Percent Composition:

o To Calculate Percent Composition:

; Experimental Data:

; Non-Experimental Data

Examples:

a) What is the percent composition of water?

b) A sample of unknown compound with a mass of 0.2370 g is extracted from the

roots of a plant. Decomposition of the sample produces 0.09480 g of carbon,

0.1264 g of oxygen and 0.0158 g of hydrogen. What is the percent

composition of the compound?

c) Find the percent composition of a compound that contains 2.30 g of sodium,

1.60 g of oxygen and 0.100 g of hydrogen in a 4.00 g sample of the compound.

Empirical Formula:

The empirical formula can be determined using:

To Determine an empirical formula:

Examples:

a) A compound was analyzed and found to contain 15.5 g Ca, 10.8 g O and

0.675 g H. What is the empirical formula of the compound?

b) Determine the empirical formula for a compound containing 2.128 g Cl

and 1.203 g Ca.

c) Determine the empirical formula for a compound containing 7.30 g Na,

5.08 g S and 7.62 g O.

Molecular Formula:

o The molecular formula is always:

o To Determine the Molecular Formula:

Examples:

a) Ribose is an important sugar that is found in DNA and RNA. Ribose has a molar

mass of 150 g/mol and a chemical composition of 40.0% carbon, 6.67% hydrogen

and 53.3% oxygen. What is the molecular formula for ribose?

b) Find the molecular formula for a compound that contains 4.90 g N and 11.2 g O. The

molar mass of the compound is 92.0 g/mol.

c) Beta-carotene, a compound found in carrots, can be broken down to form Vitamin A.

the empirical formula for beta-carotene is CH. The molar mass of beta-carotene is 57

536 g/mol. What is the molecular formula?

Report this document

For any questions or suggestions please email
cust-service@docsford.com