Chemistry
Star Test Review Notes
Solutions- TO KNOW: Solute- the matter being dissolved (salt in water, the salt is the solute)
Solvent- the matter doing the dissolving (salt in water, the water is the solvent)
Solution- combination of solute and solvent (Homogeneous material- uniform throughout) Will go through filter paper (glass of tea)
Heterogeneous- matter that is not uniform throughout- what makes it up is not evenly distributed- one part looks different from another- the particles will settle after a period of time (paint)
Homogeneous- matter that is uniform throughout- what makes it up is evenly distributed throughout (salt water)- all parts look exactly the same even under a microscope- will not settle out over a period of time
Electrolytes- solutions that will conduct a current (most ionic compounds dissolved in water are electrolytes- salt water)
Nonelectrolyte- solutions that will not conduct a current (covalent compounds dissolved in water- sugar)
Concentration of solutions- a. Molarity (M) 12M concentrated- 1.0M dilute Molarity is the number of moles of solute in a liter of solution. M= n/L b. PPM parts per million also is an expression of concentration
Likes will dissolve in likes- thus polar will dissolve in polar, fats will dissolve in fats, but fats will NOT dissolve in water (water is polar and fats are nonpolar)
Saturated solutions- a solution that does not have any more room for more solute to dissolve. (solute will fall to the bottom of the beaker)
Unsaturated- a solution that still has room for more solute to dissolve
Increasing the rate of dissolving: a. agitating (stirring)- brings more water molecules into contact w/ the solute to help pull it apart b. heating the solvent- will increase the KE of the water molecules c. crushing solutes (increasing surface area)
Molarity (measures concentration) M = n/L Find moles and change to grams by molar mass.
TYPE OF QUESTIONS: 1. A student reacts two substances in water solution at 3 C and then at 25 C. This change in temperature will have the most effect on the a. rate of the chemical reaction b. chemical nrg of the products c. level of activation energy d. molecular volume of the products
2. A 2.5 liter solution has a molarity of 0.8. How many moles of solute does this solution contain (Solution 0.8 = x/2.5 x = 2.0 n)
3. Which of the following substances is the best example of a solution a. glass of tea b. salad dressing c. table salt d. cereal in milk
4. Sugar dissolves more quickly in water at higher temperatures because a. water pressure decreases, reducing the pressure on the sugar b. water volume increases, pulling apart the sugar molecules c. water molecules speed up, increasing collisions with sugar molecules d. water molecules break apart, weakening intermolecular bonds w/ sugar
5. How many moles are needed to prepare 5.0 liters of a 2.0 M solution a. 2.5 b. 5 c. 10 d 20 2.0 = x/5.0 x = 10
Acids & Bases TO KNOW: Acids are hydrogen donators (Have H in them and lose the hydrogen), HCl) Taste sour (lemons-apples-etc) React w/ metals to produce H2 gas- Turn indicator (litmus) paper RED- pH range 1-6, w/ 1 being the most acidic Bases are OH (hydroxide) producers (Have OH in them, NaOH) (Are hydrogen acceptors) Taste bitter (soap) and feel slippery- Turn indicator paper (litmus) BLUE- pH range 8-14 w/ 14 being most basic- phenolphthalein turns PINK in a bases
Strong acids and bases are strong electrolytes (conduct electricity)
Neutralization reactions- (acid + base = salt + water)
Hydronium ion (H3O+)
TYPES OF QUESTIONS: 1. If it turns blue litmus paper red and red litmus paper red and conducts electricity and reacts w/ metal and in phenolphthalein stays clear, what is it? ACID
2. When the amino acid acts like an acid, it will donate? H
3. Which statement describes a strong acid like HCl a. it partially dissociates in solution b. it increases the pH c. it increases the OH concentration d. it completely dissociates (completely losses it H ions)
4. A sample liquid solution turns blue litmus RED. Which of the following could be the solution a. HCl b. Na c. NaCl d. C6H12O6
5. Which would be the best tool to test between acids and bases a. pH paper b. balance c. graduated cylinder d. periodic table
6. The solution with the highest acidity has a pH of a. 11 b. 7 c. 5 d. 3
Equilibrium (A + B ↔ C + D) TO KNOW:Le Chatelier’s Principle- if a system is in equilibrium and you do something to it (like adding more A, the equilibrium will shift in the direction to relieve what you did and re-establish equilibrium (It wants to stay like it was). Equilibrium: forward rate = reverse rate
Effects on equilibrium a. Concentration A + B = C + D, if you add more A the equilibrium shifts to the right to use it up, if you remove B, the equilibrium shifts to the left to make more B (wants to stay like it was) b. Temperature A + B + Heat = C + D if you increase the temperature, the equilibrium will shift to the right away from the heat, if you cool it down, it will shift to the left to produce more heat (wants to stay like it was) c. Pressure increase/ decrease pressure only affects gasses 2Ag + 3Bg = 2Cg + D if you increase pressure it will shift in the direction w/ the fewest gas molecules, thus to the right because it has 3 moles as opposed to 5 moles on the left, if you decrease the pressure it will shift to the left toward the more gas molecules
TYPES OF QUESTIONS: 1. Look at the equation showing the reaction of nitrogen w/ hydrogen N2 + 3H2 = 2NH3 + 22kcal (HEAT) What will happen to the concentration of the reactants if the temperature is decreased a. N2 decreases and H2 increases b. N2 increases and H2 decreases c.both reactants decrease d. both reactants increases (it will shift toward the right making more heat)
2. In the following reaction N2 + 3H2 = 2NH3 + 22kcal (HEAT), which change will most likely cause the forward rate to increase a. raising the temperature b. decreasing pressure c. reducing the reactants concentration d. increasing the product concentration
3. In the reaction 2H2 + CO = CH3OH + heat, which would cause a shift to the left a. increase H2 b. adding heat c. adding CO d. decreasing CH3OH
4. Consider the chemical reaction X + Y = Z + W, what change is needed to shift the equilibrium toward the reactants a. remove W b. remove X c. remove Z d. add Y
5. In the chemical reaction X + Y = Z, the equilibrium is established when the rate of formation of a. Z is greater than the formation of X b. Z is less than the formation of Y c. Z is equal to the loss of X and Y d. Z is equal to the rate of formation of X and Y
Reaction Rates TO KNOW: See PE Diagram on board (Energy vs Progress of Reaction) Activation energy is the minimum amount of energy needed to start a chemical reaction (it’s the kick in the butt to get you going) Catalysts lowers the activation nrg so the reaction can speed up. Endothermic reactions the products have more nrg than the reactants (absorb nrg thus the reaction is cooling down) Exothermic reactions the products have less nrg than the reactants (nrg is released thus the reaction heats up).
TYPES OF QUESTIONS: 1. What is the purpose of a catalyst a. reactants start at lower nrg b. it lowers the nrg barriers for the reaction to occur c. it has a strong attraction for anions and cations d. it reacts independently of temperature and pressure
2. In which type of reaction does the heat of a system flow from the surroundings into the system a. exergonic b. endothermic(absorb nrg) c. exothermic d. static
States of Matter TO KNOW: See Phase Diagram on board (solid- heat of fusion- liquid- heat of vaporization- gas) Joules (heat nrg) = m(change in temperature) Specific heat value J=m(ΔT)Cp 1 calorie = 4.18 joules) Calories = m(ΔT) Cp use 1.0 as Cp of liquid water. Diffusion- random movement of molecules from an area of high concentration to area of low concentration.
TYPES OF QUESTIONS: 1. What is the final temperature when 10.0 g of water at 25 C absorbs 50 calories of heat a. 20. 0 C b. 23.8 C c. 30.0 C d. 500 C Heat = m(ΔT)Cp 50= 10(x-25)1.0 = 30.0
2. Average KE of molecular motion is defined as a. molarity b. pressure c. temperature d. volume
3. How much heat is released as 80 g of water cools from 70 C to 55 C a. 0.19 cal b. 5.3 cal c. 1200 cal d. 5600 cal Heat = m(ΔT)Cp x = 80(15)1.0 x = 1200
Nuclear TO KNOW: Particle identification- Alpha 42He, Beta 0-1e, Positron 0+1e, Proton 11H, Neutron 10 n ,Gamma(nrg) (most damaging to human tissue) Types of decay – alpha 42He is on the product side- beta decay 0-1e is on the product side- Electron capture, 0-1e is not the reactant side
Balance nuclear equations 137N = 0+1e + ______136C 23392U = 22990Th + ____ 42He
Nuclear force (holds the nucleus together) what is going on in the nucleus P+/P+ repulsion
Stability- for the nucleus to be somewhat stable you want a 1: 1.5 proton to neutron ratio
TYPES OF QUESTIONS: 1. 23892 U = 23490Th + ______a. alpha b. beta c. gamma d. neutron
2. Which of the following naturally occurring isotopes is radioactive a. O-16 b. Ne-20 c. N-14 d. C-14
Review other material TO KNOW:
BONDS Covalent (between nonmetals) vs Ionic bonds CsC l (cations + w/ anions -) (metal w/ nonmetal) vs Metallic (holds metals together) (nitrogen- carbon are known to form triple bonds) (Lewis Structures)
BALANCING EQUATIONS-
PERIODIC TABLE (family names- valance electrons- metals/metalloids/nonmetals) (group 1 lose electrons easiest, group 17 gain electrons easiest and group 18 do not react) (atoms get bigger moving down a group and bigger moving left across a period) (X with 5 electrons around it would be in what group- group 15)
GAS PRESSURE (PV/T = PV/T, PV=nRT, barometer measure atmospheric pressure) (STP = 1.0 atm or 760 mmHG or 101.325 kPa and 0 C or 273K)(diffusion- random scattering of gas molecules) (absolute zero 0K when all molecules stop moving)(Pressure and temperature are directly related and pressure and volume are inversely related) Convert C to K by adding 273
BIOCHEMISTRY ( amino acids are protein)(Glucose is sugar and sugars combine to make starch)
MOLES & MOLAR MASS grams to moles (molar mass) , moles to molecules (6.023 x1023), grams to molecules
STOICHIOMETRY – use a balanced equation to help solve (1 mole of gas at STP will occupy 22.4 liters) mass to moles to mole ratio to mass, volume to volume (volume to mole ratio)
% yield = actual (experimental)/theoretical (calculated) If over 100% usually means water is still in the compound
THERMOCHEMISTRY- Exothermic (releases heat nrg- hotter) Endothermic (absorbs heat nrg-colder) Heat will flow from the hotter item into the colder item.
GRAPHS- Pay close attention to what the lines are labeled to help answer the question.
TYPES OF QUESTIONS: 1. Two moles of Carbon 12 have the same mass as a. one mole of Cr metal b. one mole of water c. one mole of Mg d. one mole of Li2O (know that one mole = molar mass, thus 2n of Carbon = 2(12)= 24g, thus Mg has a molar mass of 24
2. Which of the following contains 10 moles of particles a. 6.022 x1023 Cu atoms b. 790.0 g of Au c. 20.2 g of H2 molecules d. 6.022 x1022 CO2 molecules (10n(2.0g/n)= 20.2)
3. Compared to one mole of water, one mole of carbon dioxide has the same a. atomic number b. bond strength c. molecular mass d. number of molecules (1 mole = 6.022 x1023 particles)
4. The reason salt crystals, such as KCl, hold together so well is because the cations are strongly attracted to a. neighboring cations b. the protons in the neighboring nucleus c. free electrons in the crystals d. neighboring anions
5. Fire extinguishers spray solid carbon dioxide on fire. This method works because carbon dioxide a. displaces the oxygen b. renders the fire’s fuel non flammable c. forms water vapor d. blows the fire out with strong wind current
6. In order to advanve to the level of a theory, a hypothesis should be a. obviously accepted by most people b. a fully functional experiment c. in alignment with past theories d. repeatedly confirmed by experimentation
7. Which element has four electrons available to form four covalent bonds a. B b. P c. Se d. Si