Name:
Date:
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Chemistry B
BENCHMARK 3 STUDY GUIDE
STANDARDS ADDRESSED
UNIT 7: ACIDS & BASES
5a Students know the observable properties of acids, bases, and salt solutions.
5b Students know acids are hydrogen-ion donating and bases are hydrogen-ion accepting substances.
5c Students know strong acids and bases fully dissociate and weak acids and bases partially dissociate.
5d Students know how to use the pH scale to characterize acid and base solutions.
UNIT 8: THERMOCHEMISTRY
7a Students know how to describe temperature and heat flow in terms of the motion of molecules (or atoms).
7b Students know chemical processes can either release (exothermic) or absorb (endothermic) thermal energy.
7c Students know energy is released when a material condenses or freezes and is absorbed when a material evaporates or melts.
7d Students know how to solve problems involving heat flow and temperature changes, using known values of specific heat and latent heat of phase change.
UNIT 9: REACTION RATES & EQUILIBRIUM
8a Students know the rate of reaction is the decrease in concentration of reactants or the increase in concentration of products with time.
8b Students know how reaction rates depend on such factors as concentration, temperature, and pressure.
8c Students know the role a catalyst plays in increasing the reaction rate.
9a Students know how to use Le Châtelier’s principle to predict the effect of changes in concentration, temperature, and pressure.
9b Students know equilibrium is established when forward and reverse reaction rates are equal.
UNIT 10: BIOCHEMISTRY
10a Students know large molecules (polymers), such as proteins, nucleic acids, and starch, are formed by repetitive combinations of simple subunits.
10b Students know the bonding characteristics of carbon that result in the formation of a large variety of structures ranging from simple hydrocarbons to complex polymers and biological molecules.
10c Students know that amino acids are the building blocks of proteins.
UNIT 11: NUCLEAR CHEMISTRY
11a Students know protons and neutrons in the nucleus are held together by nuclear forces that overcome the electromagnetic repulsion between the protons.
11c Students know some naturally occurring isotopes of elements are radioactive, as are isotopes formed in nuclear reactions.
11d Students know the three most common forms of radioactive decay (alpha, beta, and gamma) and know how the nucleus changes in each type of decay.
11e Students know alpha, beta, and gamma radiation produce different amounts and kinds of damage in matter and have different penetrations.
UNIT 7: ACIDS & BASES
KEY VOCAB
Acid Dissociation
Base Strong vs. weak
H+ / OH- Neutralization
Arrhenius pH
Bronsted-Lowry electrolyte
KEY POINTS
· Acids are characterized by a sour taste, turning litmus paper red, and reacting with metals to form H2 gas.
· Bases are characterized by a bitter taste, slippery feel, and turning litmus paper blue
· Both acids and bases are electrolytes, meaning they can conduct electricity
ACID / BASEARRHENIUS / Produces/donates H+ / Produces/donates OH-
BRONSTED-LOWRY / Produces/donates H+ / Takes or accepts H+
Examples
Arrhenius base: NaOH (donates its OH-)
Bronsted-Lowry base: NH3 (takes H+ from H2O in the following equation to become NH4+)
NH3 + H2O à NH4+ + OH-
· Dissociation occurs when acids, bases, or salts break apart into ions; these ions are able to conduct electricity
o Acids dissociate to produce H+ + an anion (negative ion) (Ex: HCl à H+ + Cl-)
o Bases dissociate to produce a cation (positive ion) + OH- (Ex: NaOH à Na+ + OH-)
o Salts dissociate to produce a metal cation and a nonmetal anion (Ex: NaCl à Na+ + Cl-)
· A strong acid or base dissociates completely (100%)
o Examples: hydrochloric acid (HCl), sodium hydroxide (NaOH)
· A weak acid or base dissociates partially (from 0 to 99.9%)
o Examples: acetic acid (CH3COOH), ammonia (NH3)
· Neutralization occurs when you react an acid and a base; they produce salt and water
o Example: HCl + NaOH à NaCl + H2O
o The pH becomes 7 (neutral)
· pH is a scale from 0-14 that measure how strong an acid or base is
o anything less than 7 is an acid; more than 7 is a base
o closer to 0 = stronger acid, closer to 14 = stronger base
o each number on the pH scale is 10x stronger or weaker than the next number
PRACTICE PROBLEMS
1. Why does a solution with table salt (NaCl) conduct electricity when a sugar solution (C6H12O6) doesn’t?
2. Identify each acid and base in the reactions and classify as Arrhenius or Bronsted-Lowry:
a. H2SO4 + Ca(OH)2 à H2O + Ca(HSO4)2
b. H3PO4 + NH3 à H2PO4- + NH4+
c. NH3 + H2O à NH4+ + OH-
3. Classify as acid, base, or neutral
a. Pure water d. tastes sour
b. pH = 2 e. common household cleaners
c. pH = 8 f. turns litmus paper red
4. How do the following dissociate or neutralize?
HBr à ______+ ______HBr + NaOH à ______+ ______
CsOH à ______+ ______H2SO4 + Ca(OH)2 à ______+ ______
NaBr à ______+ ______
H2SO4 à ______+ ______
5. Which of the following solutions shows a strong acid? Weak acid? How do you know?
UNIT 8: THERMOCHEMISTRY
KEY VOCAB
Heat Specific heat
Temperature Latent heat
Exothermic Heating curve
Endothermic Phase change
Enthalpy
KEY POINTS
· Temperature is a measure of how hot or cold something is based on how fast the molecules are moving, also known as kinetic energy
o Temperature is measured in Celsius (°C) or Kelvin (K)
· Gases have the highest temperature/kinetic energy, solids have the lowest temperature/kinetic energy
· Heat is the transfer of energy between two objects due to a difference in temperature
o Heat is measured in Joules (J) or kilojoules (kJ)
· An exothermic reaction releases heat as a product (on the right of an equation)
o Reactants à Products + Heat/Energy
o Usually, when an object gets colder (it freezes/condenses), it undergoes an exothermic process
o Ex: liquid water freezes into solid
· An endothermic reaction absorbs heat as a reactant (on the left of an equation)
o Reactants + Heat/Energy à Products
o Usually, when an object gets hotter (it melts/evaporates), it undergoes an endothermic process
o Ex: a pot of water boils into gas
· Specific heat is the energy required to raise the temperature of 1 gram of a substance by 1 degree Celsius
· Latent heat is the energy absorbed or released as a substance changes phases
· To calculate the heat required for a substance to change temperature (specific heat) or change phase (latent heat), you need the equations below:
o Specific heat: q = m x Cp x ΔT
§ m = mass, Cp = specific heat, ΔT = change in temperature
o Latent heat: q = m x ΔH
§ m = mass, ΔH = heat of fusion/vaporization/etc. (ΔH is usually given)
· Heating curve graphs the temperature and phase changes of a substance over time as heat is added
PRACTICE PROBLEMS
1. Draw the molecules in a gas, liquid, and solid, and describe how they act differently. How are they different in terms of molecular motion? Kinetic energy? Temperature?
2. Identify the following as endothermic or exothermic:
a. The ice melts in a glass of water ______
b. The water freezes into ice cubes ______
c. A nuclear bomb explodes and releases energy ______
d. A car engine combusts, producing exhaust heat ______
e. An ice pack absorbs energy from your body ______
f. 8H2 + S8 à 8H2S + 1026 J ______
g. 2POCl3(g) + energy à 2PCl3(g) + O2(g) ______
h. N2(g) + O2(g) + heat à 2NO(g) ______
3. The specific heat (Cp) of copper is 0.4 J/oC. How much heat is needed to change the temperature of a 40 g sample of copper from 20.0 oC to 50.0 oC?
4. What would the specific heat (Cp) of a substance be if it took 400J to increase the temperature of a 20 g sample by 8 oC ?
5. Calculate the energy to melt 2 kg ice at 0 oC to water at 0 oC. (ΔHfusion of ice = 334 J/g)
6. On the heating curve above (under the key points), indicate which sections involve a substance changing temperature and which sections involve a phase change (where temperature doesn’t change). Which of these sections would you use the specific heat equation? Which of these sections would you use the latent heat equation?
UNIT 9: REACTION RATES & EQUILIBRIUM
KEY VOCAB
Reaction rate
Collision theory
Reaction coordinate
Catalyst
Activation energy
Equilibrium
Le Chatelier’s Principle
KEY POINTS
· Reaction rate is defined as:
o the decrease in concentration of reactants over time
o the increase in concentration of products over time
· Reactions occur when molecules collide (collision theory)
· A reaction coordinate graphs the energy associated with a reaction
· Activation energy is the amount of energy required for a reaction to go to completion
· A catalyst speeds up the reaction rate by lowering the activation energy:
· Equilibrium is established when the rate of forward reaction equals the rate of reverse reaction
· The concentration of reactants and products do not change during equilibrium
· Equilibrium is dynamic (reactions keep on going & do not stop)
· Le Chatelier’s Principle: if a system is at equilibrium is disturbed by a change in concentration, temperature, or pressure, the system will shift to counter this change.
o Concentration
§ the equilibrium shifts away from the side you add to and towards the side you remove from
o Temperature
§ if you increase temperature, the equilibrium shifts away from the side with heat
§ if you decrease temperature, the equilibrium shifts towards the side with heat
o Pressure
§ If you increase the pressure, the equilibrium shifts towards the side with fewer molecules
§ If you decrease the pressure, the equilibrium shifts towards the side with more molecules
PRACTICE PROBLEMS
1. As you decrease temperature, the rate of reaction ______.
2. As you increase concentration of reactants, the rate of reaction ______.
3. As you decrease pressure, the rate of reaction ______.
4. What is a catalyst? How does it affect the activation energy? Draw the effect of a catalyst on the reaction coordinate for #5 using a dotted or dashed line.
5. Draw a reaction coordinate below and label: reactants, products, and activation energy
6. Use the following reaction for the next 5 questions. You can answer shift left, shift right, or no effect.
C3H8 + 5O2 ⇌ 3CO2 + 4H2O + heat
a. If I decrease the temperature, then the reaction will ______
b. If the pressure is increased, then the reaction will ______
c. If more CO2 is added to the system, then the reaction will ______
d. If C3H8 is removed, then the reaction will ______
e. If H2O is added, then the reaction will ______
7. Predict the effect of decreasing the volume of the container for each equilibrium below:
(a) 2H2O(g) + N2(g) ↔ 2H2(g) + 2NO(g)
(b) SiO2(s) + 4HF(g) ↔ SiF4(g) + 2H2O(g)
(c) CO(g) + H2(g) ↔ C(s) + H2O(g)
8. Predict the effect of decreasing the temperature on the position of the following equilibria.
(a) H2(g) + Cl2(g) ↔ 2HCl(g) + 49.7 kJ
(b) 2NH3(g) + 37.2 kJ ↔ N2(g) + 3H2(g)
(c) CO(g) + H2O(g) ↔ CO2(g) + H2(g) + 27.2 kJ
UNIT 10: BIOCHEMISTRY
KEY VOCAB
Polymer Monomer/Subunit
Protein Amino acid
Nucleic acid Nucleotide
Starch Glucose
KEY POINTS
· A polymer is a chemical compound consisting of repeating units called monomers (or subunits)
· Proteins are polymers made out of monomers called amino acids
· Nucleic acids are polymers made out of monomers called nucleotides
· Starch is a polymer made out of monomers called glucose
· The element carbon likes to bond with a lot of atoms because it has 4 valence electrons
· Carbon can make single, double, & triple bonds
· Most organic life is made out of carbon-containing compounds
PRACTICE PROBLEMS
1. Which of the above are subunits of protein? ______
2. Which of the above are monomers of starch? ______
3. Which of the above are subunits of nucleic acids? ______
4. Which of the above is a hydrocarbon? ______
UNIT 11: NUCLEAR CHEMISTRY
KEY VOCAB
Force E=mc2
Gravity Isotope
Electromagnetic Average atomic mass
Strong nuclear force Radioactive decay
Weak nuclear force Alpha decay
Nuclear fusion Beta decay
Nuclear fission Gamma decay
KEY POINTS
· A force is a push or a pull
· Gravity is the pull or attraction between any two objects based on their mass
· Electromagnetic force is the attraction between opposite charges or the repulsion between like charges
· The strong nuclear force holds the nucleus of an atom together
o It is stronger than the electromagnetic repulsion between the protons that wants to pull the nucleus apart
· The weak nuclear force that makes certain elements radioactive
· Nuclear fusion is when two atomic nuclei combine to form one new atom
· Nuclear fission is when a heavy nucleus splits into smaller, more stable nuclei
· Einstein’s equation E=mc2 describes how a small loss in mass (m) of a nucleus is converted into large amounts of energy (E)
· Isotopes are atoms of the same element with different number of neutrons
o Isotopes therefore have different atomic masses
o Radioactive isotopes have unstable nuclei that break apart over time
· Radioactive decay is the spontaneous breakdown of a nucleus into a smaller nucleus and radiation
· The 3 forms of radioactive decay are alpha (α), beta (β), & gamma (γ) decay
· Alpha (α) decay releases an alpha particle (42He) as radiation
o Travels a few centimeters through the air