Chemical Quantities– What's the matter?

– Matter is made up of either elements or compounds.

– Elements are pure substances made of one kind of atom. They cannot be broken down into simpler chemical substances.

– Compounds are two or more elements chemically combined into an unchangeable proportion. They can be broken down into simpler substances.

Demonstration: Sugar(C12H22O11) & Sulfuric Acid( H2SO4)(draw in your notes)

– Sugar is made from carbon, hydrogen and oxygen. The reaction causes bonds to break(absorb energy) and form new ones(release energy) into carbon and water(H2O)

Everything!

Elements & CompoundsReview:•Chemical symbols indicate the element.•Chemical formulas indicate how many atoms of each element.

• Formulas are ratios

•Example: A molecule of sucrose, chemical formula - C12H22O11

• 12 atoms of carbon• 22 atoms of hydrogen• 11 atoms of oxygen

•How much of the sugar molecule is made from carbon? Or hydrogen? Or oxygen?

• Some elements are smaller in mass than others• Example: hydrogen has 22 atoms in sucrose

nearly twice as that of oxygen or carbonOnly makes up 6.49% of the sucrose molecule

Elements & Compounds• Atomic Mass: The weighted average of the masses of all the

isotopes of an element.• Found on the Periodic Table• Measured in amu (atomic mass units)

• Example: Atomic mass of carbonhydrogenoxygen

• Formula Mass: the sum of the atomic masses of all the atoms in a chemical formula.

• Example: C12H22O11 carbon: 12.01amu x 12 atoms =hydrogen: 1.01amu x 22 atoms =oxygen: 16.00amu x 11 atoms =

= 16.00 amu

144.12amu 22.22amu+ 176.00amu 342.34amu

Find the formula masses for:•Na2SO4

•CH2O• Fe2O3

• C6H12O6

= 12.01 amu= 1.01 amu

Percent Composition Percent composition: percent by mass of a element that is

contained in a compound total mass of the element divided by the total mass of the

compound, multiplied by 100.

Example: What percent does hydrogen make up in Sucrose, C12H22O11?

Carbon: 12 atoms x 12.01amu =Hydrogen: 22 atoms x 1.01amu =Oxygen: 11 atoms x 16.00amu =

+144.12amu + 22.22amu+176.00amu 342.34amu

% comp = 22.22amu 342.34amu

x100

% comp = 6.49%

Percent Composition % composition by mass Formula works with just mass in gramsExample: 200.grams of sugar was decomposed into

84.5grams of carbon. What percent is carbon in the sucrose?

84.5g carbon 200.g sucrose% mass of carbon = x 100

% mass of carbon = 42.25%

Percent Composition• Hydrate – a substance that has a specific number of water

molecules bonded to each of its formula units.• Often a salt• Example: sodium carbonate decahydrate: Na2CO3∙10H2O

• The dot represents a loose bond between Na2CO3 and H2O• Coefficient shows how many water molecules are in the

formula

• How much water is in the hydrate Na2CO3∙10H2O ?• Use % composition formula

Density●Review:●Mass – the amount of matter in a given object

●Measured in grams & kilograms●Volume – the amount of space an object takes up

●Measured in liters or cm3(cubic centimeters)● Mass and volume are extensive properties- properties that depend on how much of it one has

●Density- the amount of mass per unit volume of a substance.●how much stuff is in a particular substance●intensive property- physical properties that do not rely on the

amount●for pure substances, density does not change whether one has 1

gram of a substance for 1,000,000 grams.●Densities of several substances are found on the R.T.

●Formula:

Unit is either g/mL or g/cm3

Density = mass

volume

Density● What is the density of 100.0 grams of water that is contained in a 100.0mL graduated cylinder?

What is the volume in milliliters of 75 grams of corn oil that has a density of 1.15 g/mL?

What would the volume be for 200. grams of aluminum(Aluminum density is listed on Pg.1 of NC R.T.) ?

Empirical Formula

● Molecular formula tells us the precise number of atoms in a compound● Empirical formula – the simplest ratio of atoms in a compound

●Ex. glucose: C6H

12O

6●ratio is 6:12:6, which can be reduced to 1:2:1●therefore, the empirical formula for glucose is CH

2O

●Ex: N2H

4→

C3H

6→

Na2CO

3→

NH2

CH2

Na2CO

3

Empirical FormulaMolecular Formula from Empirical Formula

· Determine the molecular formula for hydrazine if the empirical formula is NH2 and the formula mass is 32.06amu.

Step 1: Find the empirical formula mass.nitrogen: 1 atom x 14.01amu =hydrogen: 2 atoms x 1.01amu =

Step 2: Divide the formula mass given by the empirical formula mass.

Step 3: Take the result and multiply it the number of atoms in the empirical formula

14.01amu+2.02amu16.03amu

formula mass: 32.06amuempirical formula mass: 16.03amu

= 2

N(1x2)H(2x2) = N2H4