Grade 11 Pre-AP Chemistry - Unit 2 Review

Word Equation

an equation in which the reactants and products in a chemical reaction are represented by words

Skeleton Equation

a chemical equation that has unbalanced reactants and products

Balanced Equation

a chemical equation that has balanced reactants and products

What do you do if you have an odd number of an element on one side and an even number on the other (and everything else is balanced)?

put the odd number as a coefficient on the side with the even number, and double all other coefficients

Synthesis

2 or more elements/molecules join to form a larger compound

A + B → AB

Decomposition

a large compound breaks down into 2 or more elements/molecules

AB → A + B

Single Displacement

an element replaces part of a compound

A + BC → AC + B

Double Displacement

2 compounds react and switch partners

AB + CD → AD + BC

MIN

molecular, ionic & net ionic equations

molecular: formulas of each chemical + their state

ionic: each compound listen as (aq) is split up into its ions

net ionic: shows the remaining ions + compounds that actually undergo a chemical reaction

Combustion

fuel (typically a hydrocarbon CxHy) burns in oxygen

2 types: complete and incomplete

complete: enough oxygen for fuel to burn properly

CxHy + O₂ → CO₂ + H₂O

incomplete: not enough oxygen for fuel to burn properly

CxHy + O₂ → C + CO + CO₂ + H₂O

Signs of Complete Combustion

blue flame

no smoke

no ash

no soot

Sign of Incomplete Combustion

red/orange flame

smoke

ash

soot

Tips to Remember

→assume complete combustion unless hinted otherwise

→carbonates decompose into oxide of whatever element and CO₂

→chlorates decompose into chloride of whatever element and O₂

→if 2 compounds share an element, they are undergoing synthesis

→assume most common charge of multi-valent ions unless hinted otherwise

Redox Reaction

electrochemical reaction, exchange of e⁻'s

reduction + oxidation

reduction: gain of electrons

oxidation: loss of electrons

Why does oxidation and reduction occur at the same time?

so an exchange of e⁻'s can occur

What types of reactions can be redox reactions?

synthesis, decomposition, single displacement, and combustion

Oxidizing Agent

the substance that takes the electrons in to allow the oxidation to occur

Reducing Agent

the substance that gives the electrons to allow the reduction to occur

Rule 1 of Oxidation #'s

the oxidation number of a lone element is 0

group 1 metals +1, group 2 metals +2

Rule 2 of Oxidation #'s

the oxidation number of a monatomic ion is equal to the charge of the ion

Rule 3 of Oxidation #'s

the oxidation number of oxygen is -2, except in H₂O₂ and other peroxides where it is -1

Rule 4 of Oxidation #'s

the oxidation number of hydrogen is +1, except in binary compounds with metals where it is -1 (e.g. CaH₂)

Rule 5 of Oxidation #'s

the oxidation number of fluorine is -1

all other halogens (Cl, Br, I) have an oxidation number of -1 in binary compounds, except when the other element is another halogen above it in the PT, or the other element is oxygen

Rule 6 of Oxidation #'s

the sum of the oxidation number of the atoms in a compound is 0

the sum of the oxidation number of the atoms in a polyatomic ion equals the charge of the ion

How do you Balance Redox Reactions?

(if in acidic solution):

1. write a 1/2 reaction for each process (oxidation & reduction)

2. balance each 1/2 reaction for all elements except H and O

3. balance the O atoms in each 1/2 reaction by adding H₂O molecules as needed

4. balance the H atoms in each 1/2 reaction by adding H⁺ ions as needed

5. balance the charges in each 1/2 reaction by adding e⁻'s as needed

6. multiply each 1/2 reaction by a coefficient to ensure the same # of e⁻'s is being lost and gained

7. add the 1/2 reactions together + cancel if possible

(if in basic solution):

8. add OH⁻ ions to balance any H⁺ ions on either side

9. if H⁺ and OH⁻ appear on the same side, combine them to make H₂O + cancel if possible

Radioisotope

atoms that undergo changes to their nucleus

will undergo radioactive decay, emitting energy + radiation from their nucleus as they form a new element

2 Main Factors that Determine an Atoms Stability

neutron to proton ratio

total # of nucleons (p+n) inside the nucleus

n:p ratio for Smaller Atoms that Results in a Stable Nucleus

1:1

n:p ratio for Atoms with Z (# of protons) > 20

1.5:1

Transmutation

nuclear decay resulting in a new element(s) forming

Artificial Transmutation

if the nuclear change is induced

Types of Nuclear Reactions

1. Alpha Decay

2. Beta Decay

3. Gamma Decay

4. Positron Emission

5. e⁻ Capture

6. Fission

7. Fusion

Alpha Decay

an alpha particle is emitted from the nucleus, leaving a smaller nucleus behind

4 He

2

(an alpha particle is a helium atom that has lost its e⁻'s)

(large particle, can be blocked by a piece of paper)

Beta Decay

e⁻ emitted from the nucleus when a neutron breaks down

0 e

-1

(smaller particle, requires thicker + denser materials to block it, like Al foil)

Gamma Decay

pure E

gamma rays don't change the nucleus, but decreases the total E it has

(upside down fish with 2 circles on left side)

(have very high E, require several feet of metal/lead to absorb)

(use either a * or m beside the mass to show the high E isotope, then without it after the E is released)

Positron Emission

a positive version of an electron/beta particle

0 e

+1

e⁻ Capture

the e⁻ is a reactant

Fission

larger nuclei break down into 2 or more smaller nuclei

Fusion

2 or more smaller nuclei combine to make 1 larger nuclei

What do you do if you are missing mass but the charges balance?

neutrons are being emitted

1 n

0