Final Exam Review Guide with Practice Questions Unit 6 Stoichiometry Standard: Solving for quantities in a chemical equation I can describe the units: mole, gram, Liter, formula units What is the difference between all the units mentioned? Mole: measure of the amount of a substance Gram: measure of the mass of a substance Liter: measure of the volume of a substance Formula Units: Measure of the number of the smallest indivisible part of a substance i.e atoms or molecules I can convert between units of mole, gram, Liter and formula units How many liters are present in 13.95mol? (19.95 mol)(22.4L) = 446.88 L How many atoms are in 2.3 mol of N2 gas? (2.3 mol)(6.022X1023 molecules) = 1.38X1024 molecules X 2 atoms per molecule = 2.77 X 1014 How many moles are in 32 grams of CH4? 32 g/ 16 g per mol = 2 mol I can explain what a chemical equation means with regard to how many reactants used and products formed What do the coefficients actually mean in: 2H2O O2 + 2H2 Coeffients in an equation represent how many moles and/or molecules are required for each reactant to produce each product. Very similar to how a recipe works in a cookbook. I can determine a mole ratio using a chemical equation SiO2 + 4HF SiF4 + 2H2O How many moles of water are made for every hydrogen fluoride? 1 mol Hf X (2 H2O/4 HF) = 0.5 mole of water I can convert between reactants and products using mole ratios 4NH3 + 5O2 4NO + 6H2O If you have 6 moles of ammonia, how much water can you make in moles? 6 mol NH3 X (6 H2O/4 NH3) = 9 mol of water I can convert moles, grams, Liters and formula units of reactants/products into units of moles, grams, Liters and formula units of another reactant/product using mole ratios 4NH3 + 5O2 4NO + 6H2O. How many atoms of O2 oxygen are produced from required to form 199.4grams of NO? (199.4 g NO/ 30 g per mole) X (5 O2/ 4NO) X (6.022X1023) X (2 atoms per molecule) = 1.0X1023 atoms of oxygen Standard: Solving for Limiting Reagent/Excess Reagent I can explain limiting and excess reactants What is the difference between the two? A limiting reactant will run out of its designated quantity first. This means the reaction will be limited by how much of that particular reactant you have. An excess reactant means you have more than enough of the particular reactant. I can determine the limiting and excess reactant using mole ratios SiO2 + 4HF SiF4 + 2H2O. If 4.6mol HF is reacted with 3.9mol SiO2 which is the limiting reactant? 4.6 mol HF/4 = 1.15 reactions (Limiting Reactant) 3.9 mol SiO2/ 1 = 3.8 reactions I can determine the limiting and excess reactant by converting from grams, Liters or formula units and then using the mole ratio of the reactants SiO2 + 4HF SiF4 + 2H2O. If 50 grams HF is reacted with 30 grams SiO2 which is the limiting reactant? (50 grams HF/20 g per mol)/ 4 = 0.625 reactions (30 grams SiO2/ 1 g per mol)/ 1 = 0.499 reactions (Limiting Reactant) I can determine how much product is made by using the limiting reactant SiO2 + 4HF SiF4 + 2H2O. If 120 grams HF is reacted with 3.9mol SiO2, how much water is produced? (120 grams HF/20 g per mol)/ 4 = 1.5 reactions (limiting reactant) (3.9 mol SiO2/ 1 mol) = 3.9 reactions 6 mol of HF from above X (2 H2O/4 HF) = 3 mol of water produced Standard: Calculating Percent Yield I can determine how much product should be made using stoichiometry *See above practice problems I can identify the difference between how much product should be produced compared to what was actually produced in an experiment A scientist calculated he will collect 123 grams of water in a decomposition reaction. When he massed the amount of water from his experiment, he collected 120 grams. Which is the theoretical and which is the experimental? 123 grams = theoretical 120 grams = experimental I can determine the percent of product collected from an experiment based on how much should have formed You calculate a reaction to produce 15.62grams but it actually produced 11.08grams. What is the % yield? (11.08g/15.62g) X 100 = 70.93% Unit 7: Gas Laws Standard 1: Combined Gas Laws I can explain all three gas laws and how the variables affect one another Describe each variable in the combined gas law equation. Pressure: The amount of collisions the gas is exerting on itself and the container Volume: The measure of space the gas occupies Temperature: Always in Kelvin is the average kinetic energy of all the atoms of gas. Explain how the other variables are affected if T increases. What is V decreases? What is P increases? If temperature increases, particles are moving faster and colliding more often which increases pressure and would therefore increase the volume of the container. *Be careful with this though because we usually talk about only two variables at a time due to the fact that the three will interact in different ways. For example, when pressure increases the container would increase in volume, but once the container has more space you have less collisions and the pressure returns to the original value. So, try explaining only two variables at a time and assume the other one is constant like in a rigid container that cannot change volume. If volume were to decrease the pressure would increase because the gas would collide more in tight space. If pressure were constant, then the temperature were increase instead. If pressure increased on the container the volume would decrease. If volume were constant then the temperature would increase. I can solve for unknown variables in the combined gas law equation Calculate the pressure of a gas with volume= 126mL, n=4.53, and T= 35C. PV=nRT (P)(.126 L)=(4.53 mol)(0.0821 atm*L/mol*K)(308K) P = 909.1 atm I can convert units of pressure, temperature and volume to fit into a gas law problem correctly How many kPa are in 1.56 atm? 1.56 atm X (101.3 kPa/1atm) = 158.028 kPa Standard 2: Ideal Gas Law I can explain what the ideal gas law is and how each variable will impact the others What happens to pressure and temperature when the numbers of moles increases in a container? When the amount of gas is increase there are more particles colliding and more energy so the temperature and pressure would increase. I can explain the assumptions behind what an ideal gas even is and how it acts At the atomic level, describe an atom of gas and how it collides and the volume according to ideal gas law. We assume each formula unit occupies zero space and that all particles have zero attractive forces to eachother allowing for the PV=nRT math model to work correctly. However, real gases would have to account for some size of particles and slight attraction. (There is an equation for that ) I can solve for unknown variables in the ideal gas law equation Calculate the number of grams of H2O(g) with a vol= 250mL, P=2.06atm. and Temp= 416K. (2.05atm)(.25L)=n(0.0821 atm*L/mol*K)(416K) n= 0.015 mol of water X (18 g per mol) = 0.27 grams of H2O I can apply stoichiometry to help solve and explain ideal gas law problems A teacher wants to produce hydrogen gas by adding magnesium metal to hydrochloric acid, according to the balanced equation below. Mg + 2HCl MgCl2 + H2 If the teacher wants to produce 11.78 Liters of gas at room conditions of 25 °C and 1.35 atm, what mass of magnesium is required? (1.35atm)(11.78 L)=n(0.0821 atm*L/mol*K)(298K) n = 0.65 mol of H2 0.65 mol H2 X (1Mg/1H2) = 0.65 mol of Mg X (24.3 g per mol) = 15.8 g Mg I can apply the ideal gas law to determine densities of gases What is the density of Cl2 gas at STP? 1 mol of Cl2 gas = 70.9 g 70.9g/ 22.4 L = 3.17 g/L Standard 3: Graham’s Law I can explain Graham’s law What is the rate of diffusion/effusion of gases based on? How fast a gas travels is based on how much mass each particle has. The smaller the mass the faster is can diffuse or travel through holes. I can identify the rate of effusion of various gases compared to one another Which gas effuses faster: Methane or Oxygen? Methane has a molar mass of 16 g/mol while oxygen gas (O2) has a molar mass of 32 g/mol, so methane would effuse faster. I can determine the rate of effusion of gases using molar mass and the equation What would be the rate of effusion of Hydrogen Sulfide (33 g/mol) compared to Xenon? RHS/RXe = √(131.3 g/mol)/(33 g/mol) 1.99 = how fast HS is compared to xenon (This means HS effuses twice as fast) Unit 8: IMFs Standard: Phase Changes and Heating Curves I can describe all types of phase changes List every phase change and what phase of matter is the starting point and which is the end point Deposition – From a gas to a solid, exothermic/releases energy…Why? Going from a high energy state to low energy state would require a loss of energy Sublimation – From solid to gas, endothermic/requires energy…Why? Melting – From solid to liquid, endothermic/requires energy…Why? Freezing- from liquid to solid, exothermic/releases energy---Why? Boiling – From liquid to gas, endothermic/ requires energy…Why? Condensation- gas to liquid, exothermic/releases energy…Why? I can interpret a phase change diagram and create one from data Label the phases, normal boiling and freezing points, and triple point on the diagram. Show an arrow for each phase change and label it. Liquid Solid Gas Triple Point I can interpret a heating curve and create one from data Label all the phase changes and phases on the heating curve. (Be able to read the graph too.) 90 E 80 T E M P (oC) 70 D 60 50 40 C 30 20 10 B 0 -10 A 10 20 30 40 50 60 70 80 90 100 110 120 TIME (min) A = Solid B = Melting C = Liquid D = Boiling E= Gas I can explain why phase changes happen in terms of IMFs and energy Why does temperature remain constant during a phase change? All the energy, which temperature measures, is either being absorbed to break IMFs or bond, or the energy is being released to the environment when forming the bonds, and the overall substance is not gaining or losing energy. Why do liquids boil? (Involve both variables in your explanation) A liquid will boiling when the kinetic energy of the molecules is enough to escape the attractive forces holding them together. When the particles escape they exert a vapor pressure on the air around them, and if the vapor pressure exceeds the atmospheric pressure surrounding them, then the liquid will boil. Essentially, once the pressure exerted by the liquid exceeds the pressure from the air around it, then the liquid boils. You can either lower the atmospheric pressure (Vacuum) or increase the temperature of the liquid so more particles escape and the vapor pressure increases enough. Standard: Properties and Phases of Matter I can describe the properties of a solid, liquid and gas 1. Describe the properties of the following phases gas liquid solid assumes the shape and volume of its container particles can move past one another assumes the shape of the part of the container which it occupies particles can move/slide past one another retains a fixed volume and shape rigid - particles locked into place compressible lots of free space between particles not easily compressible little free space between particles not easily compressible little free space between particles flows easily particles can move past one another flows easily particles can move/slide past one another does not flow easily rigid - particles cannot move/slide past one another I can explain the kinetic molecular theory and how it relates to each phase Use the kinetic molecular theory to describe the particles energy and movement in each phase of matter. a. Solid: Low energy, strong attractive forces, fixed positions, vibrate, little space inbetween. b. Liquid: Medium energy, attractive forces (IMFs), particles can move freely, but are held down by attractive forces, some space in-between, but not much c. Gas: High energy, few if any attractive forces, particles are free to move randomly, lots of space in between particles I can diagram what each phase would look like at the atomic level Draw a diagram of the particles in each phase of matter to represent your descriptions above. Standard: Intermolecular Forces I can describe each type of IMF List the IMFs and explain the requirement for a molecule to have each type and what it is. Van der Waals/London Dispersion – Nonpolar particles have a dipole moment when electrons are unevenly distributed causing a slightly positive and negative end (poles) causing particles to have a weak attraction with one another Dipole-Dipole : Polar molecules have a permanent uneven distribution of electrons causing the molecule to have a positive and negative end like a magnet. This allows the molecules to have an attraction with each other that is stronger than London dispersion Hydrogen bonds : Polar molecules that have H bonded with O,N or F will form hydrogen bonds which are basically the strongest dipole-dipole attractions I can explain the strength of each IMF List the IMFs in order of increasing strength AND explain why each IMF exhibits that strength. London Dispersion only slight + and – ends, Dipole-Dipole larger + and – ends for stronger attraction, Hydrogen bonds with the largest + and – ends due to O, N and F having large electronegativities I can determine what IMF an atom or molecule would exhibit based on its structure or formula What is the IMF of each of the following: H2O H-Bond CH4 CH2O2 C3H8 CO2 HBr HF Dispersion H-Bond Dispersion Dispersion Dipole H-bonds Standard: Specific Heat I can explain what specific heat capacity is What does heat capacity represent? The amount of energy required to change the temperature of a substance OR how easily substances can transfer energy. I can identify which materials have higher or lower specific heats Why does water take so long to warm up, but sandy beaches are always hot during the day in summer? Water does not transfer/absorb energy easily so its specific heat is high meaning it requires a lot of energy to heat up. Sand is the opposite I can calculate all variables involved with specific heat A 25.75-g piece of iron absorbs 1200.75 joules of heat energy, and its temperature changes from 25ºC to 110ºC. Calculate the heat capacity of iron. Q=mcΔT 1200.75 J = 25.75 g * C * (110-25) C = 0.5486 J/g*Celsius How many joules of heat are needed to raise the temperature of 15.0 g of aluminum from 22ºC to 44ºC, if the specific heat of aluminum is 0.95 J/gºC? Q=15g*0.95*(44-22) Q = 313.5 J To what temperature will a 150.0 g piece of glass raise if it absorbs 10,275 joules of heat and its heat capacity is 0.50 J/gºC? The initial temperature of the glass is 20.0ºC. 10,275 J = 150 g * 0.5 * (Tf – 20) 137 = Tf – 20 157 degrees C= Tf Unit 9: Solutions and Colligative Properties Standard: Solubility and Properties of Solutions I can describe the parts to a solution Describe solute and solvent. Solute gets mixed in with a solution and is dissolved Ex: Sugar, salt, ingredients Solvent is the base of the solution and makes up the majority. Also does the dissolving. Ex: Water I can explain “like dissolves like” What does this phrase mean? Polar molecules dissolve Polar molecules Nonpolar molecules dissolve nonpolar molecules I can predict solubility based on solute and solvent polarity What types of molecules dissolve in water? Will solid carbon dioxide dissolve in oil? Other polar molecules. Yes I can identify electrolytes NaCl or Sugar? NaCl I can explain properties of electrolytes in solution What happens to electrolytes in a solution? What can they do? They dissociate into the ions that make them up. These free moving ions can conduct electricity since that is what electricity is…. I can determine if a solution is saturated, unsaturated or supersaturated How do you know when a solution is one of these terms? Unsaturated solutions can dissolve more solute Saturated solutions have the maximum solute dissolved in the solution Supersaturated solutions have more than the maximum solute dissolved in solution Standard: Net Ionic Equations I can identify whether a molecule/compound will become ions in a solution or not Can you use the solubility rules correctly? See reference I can explain what happens when two reactants dissolve into a solution Draw NaCl and Ca(NO3)2 as they would exist in a solution. I can write a complete ionic equation What is the ionic equation for: K2CO3 + Ca(NO3)2 K2CO3 + Ca(NO3)2 2KNO3 + CaCO3 2K+1 + CO32- + Ca2+ + 2 NO31- 2K+1 + 2 NO31- + CaCO3(s) I can write a complete net ionic equation What is the net ionic for the problem above? CO32- + Ca2+ CaCO3(s) Standard: Molarity I can explain concentration What does concentration mean? Concentration is a measure of how many solute particles there are in a given volume. In short, how much stuff is packed into a specific area. I can interpret pictures and diagrams based on their concentration What would a diagram of a highly concentrated solution look like at the atomic level? What about a dilute solution? I can determine the concentration of a solution using an equation Calculate the molarity of a solution made with 3.44moles in 16L of water. Standard: Colligative Properties I can describe what colligative properties are What are they? The properties of solutions that change based on how much solute is in the solution. Vapor pressure, freezing point and boiling point I can explain how colligative properties affect a solution What happens to a solution when you add solute? (3 properties change…) When solute is added: 1. The solvent particles have trouble forming IMFs and bonds to become solid. So, the freezing point is depressed 2. The solvent particles have a harder time escaping their IMFs to become gas, so the vapor pressure is decreased 3. Because the solvent particles are vaporizing less, the boiling point is elevated I can determine how much a solution will be affected by colligative properties based on number of ions added to the solvent Which molecule would change the colligative properties the most: Salt, Sugar or aluminum nitrate? How do you know? Salt = 2 ions Sugar = 1 particle Aluminum nitrate = 4 ions which would have the largest effect on colligative particles Unit 10: Acids and Bases Standard: Properties I can define acids and bases What is an Arrhenius acid and base? What about Bronsted-Lowry? Arrhenius acids and bases add H+ and OH- to solution Bronsted-Lowry acids and bases donate and accept protons I can name acids and bases What is the formula of lithium hydroxide and hydroiodic acid? LiOH and HI Name the following: HCl Sr(OH)2 H3PO4 Hydrochloric acid strontium hydroxide Phosphoric acid I can identify different types of acids and bases according to their formula Label the compounds above as Arrhenius and Bronsted-Lowry acid and bases. They are all both I can describe the properties of acids and bases What are the properties of an acid and base? Acid: • • • • • Tastes sour Reacts with bases to produce water and salt Reacts with metals to produce hydrogen gas Changes colors with indicators Conducts electricity • • • • • Feel slippery Taste bitter Change colors with indicators Conduct electricity React with acids to form water and salt Base: I can identify products we use as acids and bases What types of everyday items tend to be acidic? Basic? Can you give specific examples? Food items are acidic and cleaning items are basic. Lemons and citric juices vs. Bleach and detergents Standard: Reactions I can write equations showing how certain compounds form acidic and basic compounds What is the equation for water to react with itself and form acidic and basic ions? H2O + H2O H3O+ + OHWhat is the equation for potassium hydroxide mixing with water? What about hydrobromic acid with water? KOH + H2O K+ + OH- + H2O (Remember bases are electrolytes and become ions) HBr + H2O Br- + H3O+ (Same as the above, but the proton will exist as hydronium, H3O+ in solution) I can predict the products of an acid base reaction or a neutralization reaction Finish the equations: LiOH + HI H2O + LiI Base Acid C.A C.B. NaOH + HNO3 H2O + NaNO3 Base Acid C.A. C.B NH3 + H2O NH4+ + OH- Base Acid C.A. C.B. I can explain societal effects of acids and bases like acid rain and limestone lakes How does acid rain form? What are the effects on the environment? Why do limestone lakes not become acidic due to acid rain? Acid rain is rainwater with a lower pH. It forms when gaseous pollutants like carbon diocide and nitrous oxide react with water vapor in the air to form acidic compounds like nitric acid or carbonic acid. This rainwater can corrode metal and lower the pH of lakes and rivers which arms ecosystems. I can identify different types of acids and bases in a reaction (Bronsted, Lewis, Arrhenius) Label the three reactions you predicted the products for above. Standard: pH I can identify various testing methods to classify acids and bases List all the indicators we used in class to identify acids and bases. pH paper, red cabbage, Phenolphthalein I can describe how various testing methods work to classify acids and bases work How exactly does an indicator work? Indicators react to form new compounds which absorb and reflect different wavelengths of light, thus giving us the different colors we see when acids and bases are present I can classify acids and bases according to pH value Draw the pH scale and label the areas that are acidic, basic and neutral. Alkaline means basic I can rank acids and bases in order of strength bases on their concentrations and pH values Rank the following solutions from most acidic to least: pH=2 Most 2 5 8 12 Least Which solution is the most acidic: [H+] = 2 X 10-11 pH=12 pH=5 pH= 8 [OH-] = 2.4 X10-3 HCl with 0.035 M I can identify equations used for pH of substances HCl = .035 M What are the equation(s) used for the ionization of water? Kw = [OH-][H+] What are the equation(s) used to determine pH? pH = -log[H+] I can calculate pH based on solution concentrations or concentrations based on pH Solve the following problems: pH of a 1.2 M acid? -log [ 1.2] = -0.792 [H+] of a solution that has a pH of 4.76? 10-4.76 = 0.0000174 M pH of a solution that contains .0046 NaOH? 1X10-14 = [.0046][H+] [H+] = 2.174 X 10-12 M -log[2.174 X 10-12 M ] = pH = 11.66 I can use stoichiometry to determine mass of acid and base needed or used to make specific concentrations What mass of HNO3 would be required to make a solution that is 2M and 1.3L? 2M = mol/1.3L Mol of HNO3 = 2.6 X (63 g per mol HNO3) = 163.8 grams If you massed out 12.67 grams of HI and put it into 200mL of water, what pH would the solution be? 12.67 g HI/(128 g per mol of HI) = 0.099 mol of HI/ 0.2L = 0.495 M -log [ 0.495] = 0.3054 = pH What mass of HCl would be required to make a .45L solution have a pH of 3? 10-pH = 10-3 = [H+] = 0.001 M = mol of HCl/ 0.45 L Mol of HCl = 0.00045 X (36.45 g per mol of HCl) = 0.0164 grams of HCl Standard: Titrations I can describe an acid-base titration and the method used What is a titration? The technique used to determine the unknown concentration of an acid or base using a standard known concentration of the opposite type of solution I can explain why a titration works to determine a concentration What does the neutralization point mean? Equal number of particles of base and acid are present Describe what is happening in the solution when the indicator changes colors during a titration. See above statement on how indicators work I can determine concentrations and pH of solutions based on titration data Here are some buret readings from titrating 25mL of an unknown acid with a 0.3 M standard solution of NaOH 0.3 M NaOH initial reading: 48.7 mL final reading: 32.4 mL What is the molarity of the acid? What is the pH of the acid? What is the pH of the base? MaVa=MbVb Ma(25mL) = (0.3 M)(48.7mL) Ma = 0.5844 -log [0.5844] = pH of acid = 0.233 pH of base (which is an entirely separate solution): Kw=[0.3][H+] [H+] = 3.33X10-14 -log[3.33X10-14] = 13.48 = pH of base Unit 11: Organic Chemistry Standard: Naming and Drawing I can name and draw simple alkane hydrocarbons What are the ten alkanes? What do they look like? Methane 1C Ethane 2C Propane 3C Butane 4C Pentane 5C Hexane 6C Heptane 7C Octane 8C Nonane 9C Decane 10C I can name and draw hydrocarbons with branches Draw 2,3-methylhexane 2,3-dimethylhexane and 4-ethyl-5-propyloctane Name: 3,7,-diethyl-6-propyl-decane (the 3 carbon is actually a different name, but we will call it propyl because it is 3 carbons) I can name and draw hydrocarbons with double and triple bonds Draw ethane and 2-methyl-5-hexyne (The triple bond is on the 3 carbon, obviously it should be on the fifth) I can name and draw hydrocarbons with functional groups 1,5-dipentanol I can name and draw hydrocarbons with halogens Name both: 2-bromo-propane 1-bromo-propane Standard: Concepts and Patterns of Organic Compounds I can explain (in general) why certain compounds exhibit different characteristics like smell What role do functional groups serve on organic compounds? Why is a benzene ring referred to as an aromatic ring? (relate your explanation to its structure) Functional groups are called such because each group has a particular function due to their structure on an organic molecule. Benzene is called an aromatic rings because of its characteristic smell when present in molecules. I can explain hydrocarbons What is a hydrocarbon? A carbon chain with hydrogens surrounding them. Very stable molecules that have a lot of potential energy stored between all their bonds I can explain the difference between saturated and unsaturated fats/hydrocarbons What is the difference? Draw two saturated fats and two unsaturated fats. Saturated fats are hydrocarbons that have the maximum number of hydrogens bonded onto the carbons. This is a very stable molecule that requires immense amount of energy to break apart. Unsaturated fats have less than the maximum number of carbons and are slightly easier to break down because they are less stable and not as uniform in structure.