Chemistry Final Exam Review

Transcription

1 Chemistry Final Exam Review THE MOLE Define a mole and describe what it tells about a substance. Be able to determine the molar mass of a substance 1. Define a mole. What does it tell us about a substance? 2. Determine the molar mass for calcium acetate Ca(C 2 H 3 O 2 ) 2. Be able to determine the percent composition by mass of elements in compound. Be able to convert between units using the following conversion factors: 3. For sodium sulfate (Na 2 SO 4 ), calculate the percent composition of sodium. 1 mole = molar mass in grams = 22.4 L of a gas at STP Be able to define empirical and molecular formulas. 4. How many moles are in 30g of NaCl? 5. How many grams are in 3.00 moles of KCl? 6. Define empirical formula. 7. Define molecular formula. 8. How do you determine the empirical formula from the molecular formula? 9. Determine the empirical formula of the following molecular formulas: C 6 H 12 O 6 C 25 H 50 O 5 C 6 H How much would 100 L of water vapor weigh in grams at STP?

2 1. Balance the following equations: NaCl + Ca CaCl 2 + Na Sn(CO 3 ) 2 + K K 2 (CO 3 ) + Sn NaOH + AlPO 4 Na 3 PO 4 + Al(OH) 3 FeO + Al Al 2 O 3 + Fe Al 2 O 3 + Mg MgO + Al C 2 H 4 + O 2 CO 2 + H 2 O Na + Cl 2 NaCl 2. State the Law of Conservation of Mass. CHEMICAL REACTIONS Know what indicates that a chemical reaction has taken place: temperature change, color change, formation of a gas (bubbles), and formation of a precipitant (solid is formed when two liquids react) Know that the reactants are on the left and the products are on the right. Know how to balance the equation by adding coefficients until the numbers of atoms are equal on each side. Know how to properly use subscripts to count elements. For example, Al 2 (SO 4 ) 3 means there are 2 Al s, 3 S s and 12 O s. Know how to properly use coefficients to count elements. For example, 3Al 2 (SO 4 ) 3 means there are 6 Al s, 9 S s and 36 O s. Know that a balanced equation is a confirmation of the law of conservation of mass 3. What does the law of conservation of mass mean for us in chemistry? STOICHIOMETRY Know the steps for solving all stoichiometry problems. a. Balanced equation. Know that the coefficients for each compound represent the ratio of moles in the equation. b. Set up your proportion with the known and unknown on top, stack like units with the conversion factors. Know how to calculate the molar mass of a compound. Add up the molar mass for each element. Multiply by a coefficient. 1. Given the following reaction: H 2 O 2 H 2 + O 2, how many moles of H 2 will you make if you begin with 2.51 moles of H 2 O 2? 2. Given the following reaction: 2 ZnS + 3 O 2 2 ZnO + 2 SO 2, how many moles of ZnO will you make if you begin with 6.82 grams of O 2? Know how to calculate a reaction s percent yield. % yield = actual yield/theoretical yield Be able to define limiting reactant, excess reactant, actual yield, theoretical yield

3 3. Given the following reaction: 2 ZnS + 3 O 2 2 ZnO + 2 SO 2, how many moles of ZnO will you make if you begin with grams of O 2? 4. In the following reaction: H 2 CO 3 (aq) + 2 Na (s) Na 2 CO 3 (aq) + H 2 (g), how many grams of Na are need to make 5.0 grams of H 2? 5. From the problem above, what is the percent yield of Na if only 105 grams are made? 6. Define the following terms: a. stoichiometry b. limiting reactant c. excess reactant d. actual yield e. theoretical yield Describe the differences between the particles in a solid, liquid, and gas. 2. What does temperature tell us about a substance? 3. Describe the relationship between the following variables: a) Pressure and number of collisions b) Temperature and pressure c) Volume and pressure d) Temperature and volume

4 4. If the pressure of a gas changes from 4.5 atm to 3.75 atm, what was the original volume if the final volume was 7.55 L? GAS LAWS Know how to use the Gas Laws. The Gas Laws will be given to you. Know how inverse relationships work. (If one part is increased 5 times, the other part will decrease to 1/5.) Ex. Pressure vs. volume 5. A gas at 30 o C and 3.4 atm pressure is put under a pressure of 3.0 atm. What is the new temperature? 6. Two gases with the pressure of 1.5 atm each are placed into a gas tank. What is the total pressure in the tank? Know how direct relationships work. (If one part is increased 5 times, the other part will increase 5 times.) Ex. Pressure vs. Temp and Volume vs. Temp Know that STP is standard temperature and pressure. Standard temperature is 0 C and standard pressure is 1 atmosphere. Know Avogadro s principle conceptually and mathematically. Know how to convert moles of a gas to liters or liters to moles using 22.4 L/1 mole. Be able to solve gas stoichiometry problems at STP. 7. A gas at STP occupies 2.5 L. What volume will it occupy if the temperature is changed to 300 K and the pressure changes to 1.25 atm? Know that pressure is caused by the number of particles hitting the sides of a container. Know what can change the pressure within a container. Know how to convert o C to K or K to o C. Know that all gas law problems are solved using the Kelvin temperature scale. Be able to define diffusion vs. effusion Know the postulates of the kinetic molecular theory 8. Given the following reaction: 2 ZnS + 3 O 2 2 ZnO + 2 SO 2, how many liters of O 2 are needed at STP to form 7.5 L of SO 2? Be able to compare the properties and particle behaviors of solids, liquids, and gases. 9. In the following reaction: H 2 CO 3 (aq) + 2 Na (s) Na 2 CO 3 (aq) + H 2 (g), how many liters of hyrdrogen gas are produced at STP if you make moles of Na 2 CO 3?

5 SOLUTIONS Know that solutions are made up of two parts the solvent and the solute. The solvent is usually water and it makes up the majority of the solution. The solute is what is being dissolved and it makes up the smaller portion of the solution. Be able to describe the trends in solubility as temperature increases for a solid in water and a gas in water. Know how to interpret a Solubility Graph and determine if a solution is supersaturated, unsaturated, or saturated. Define and describe the differences between a saturated, unsaturated, and supersaturated solution. Know how to speed up the dissolving of a solute. Know what it means to dilute a solution and how to calculate it. Grams of Solute Dissolved Solubility (grams of solute/100 g of water) KNO 3 NaNO 3 LiCl KCl Temperature ( o C) SOLUTIONS (cont.) Know that like dissolves like which means polar substances will dissolve polar substances and nonpolar substances will dissolve non-polar substances. They will not dissolve each other. Know that we measure a solution s concentration by measuring the number of moles dissolved in 1 L. (molarity) Know how to determine molarity when given moles and volume or when given grams and volume Use the graph above to answer # How many grams are needed to make a saturated solution of KNO 3 at 50 o C? 2. At 60 o C, what type of solution will you have if 70 grams of KCl are dissolved in 100 g of water? Know how to determine volume when given moles and molarity. Know how to determine moles when given volume and molarity. Be able to define an electrolyte 3. If 100 grams of NaNO3 are dissolved in 100 grams of water, what must the temperature be to make it a saturated solution? 4. Calculate the molarity of a solution of sodium carbonate if 2.35 moles are dissolved in enough water to make 1.2 L of solution. 5. How many moles are needed to prepare L of a 0.3M solution of aluminum oxide?

6 6. What does it mean to dilute a solution? How would you dilute it? 7. If I have 340 ml of a 0.5 M NaBr solution, what will the concentration be if I add 560 ml more water to it? 8. If you wanted to dissolve sugar into water, what steps could you take to make it go faster? 9. Which of the following would most likely dissolve in water? Justify your answer. Carbon tetrafluoride (nonpolar) or ammonia (polar). 10. Which of the following would most likely conduct electricity in solution? Justify your answer. CCl 4 or NaHCO Determine the ph of a 0.2M solution of hydrochloric Acids and Bases acid? Be able to define strong acids/bases. Know how to calculate the ph. Be able to determine if a substance is acidic or basic based on ph. Be able to describe the properties of acids and bases: how they affect litmus paper, their taste, ph range, ions present. 2. Determine the ph of a 4.37 x 10-6 M solution of nitric acid? Define a neutralization reaction and determine the products in these reactions 3. What makes an acid/base strong versus weak? 4. What are the properties of acids? 5. What are the properties of bases? 6. What is formed when you mix an acid and base?

7 1. Define an endothermic reaction. Give an example. 2. Define an exothermic reaction. Give an example. Thermochemistry Be able to describe the difference between an exothermic and endothermic process by definition. Be able to calculate specific heat of substances Be able to define specific heat of a substance Be able to sketch and label a heating curve. 3. Define specific heat. 4. What would be the difference between heating a substance with a low specific heat and a high specific heat? 5. What is the specific heat of a substance that absorbs 25J of heat and has a change in temperature from 20C to 26C? 6. Sketch and label the states of matter and phase changes in the heating curve of converting ice to steam.