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CHEMISTRY CP FINAL EXAM REVIEW Name: 1. For each reaction below: identify the reaction type, predict the products and write the complete balanced reaction: Synthesis Decomposition Double Replacement Single Replacement Combustion a. iron (III) hydroxide → iron (III) oxide and water _ Decomposition __ ________2Fe(OH)3 → Fe2O3 + 3 H2O ___________________________ b. ethylene (C2H4) burns in pure oxygen → _ Combustion______ ________ C2H4 + 3O2 2CO2 + 2H20___________________________ __ Synthesis ________ c. magnesium + nitrogen → _________3Mg + N2 Mg3N2_________________________________ 2. Complete and balance the reactions below in the space provided. __2___KOH _____ Cl2 + _____ Pb(NO3)2 + __2___NaBr _____ Pb(OH)2 + __2___ KNO3 _2_NaCl + Br2 3. Sodium reacts with calcium chloride to produce sodium chloride and calcium metal. a. Balance __2__Na + ____CaCl2 ____Ca + __2__NaCl b. If 43.0g of calcium chloride reacts, how many grams of sodium chloride will be produced? (ans: 45.3g NaCl) 43 g CaCl2 x 1 mol CaCl2 x 2 mol NaCl x 58.5 g NaCl = 45.3 g NaCl 111.1 g CaCl2 1 mol CaCl2 1 mol NaCl c. The reaction above is performed in lab, and 40.0g of sodium chloride are collected. Determine the percent error and the percent yield. (ans: 88.3% yield, 11.7% error) % yield = 40g x 100 = 88.3% yield 45.3g % error = 100- 88.3 = 11.7 % 4. Sodium sulfate reacts with aluminum bromide. a. Balance: ___3__ Na2SO4 + ___2_ AlBr3 ___6__NaBr + _____Al2(SO4)3 b. Predict the mass of aluminum sulfate that will form if 25.0g of sodium sulfate react with 60.0g of aluminum bromide. (ans: 20.1g Al2(SO4)3) 25g Na2SO4 60g AlBr3 1mol Na2SO4 142 g 1mol AlBr3 266.7 g 1mol Al2(SO4)3 3mol Na2SO4 1mol Al2(SO4)3 2mol AlBr3 342g 1mol Al2(SO4)3 342g = 1mol Al2(SO4)3 = 20.1 g Al2(SO4)3 38.5 g Al2(SO4)3 c. The limiting reactant is: _________ Na2SO4_________________________. 5. Hydrogen reacts with nitrogen to produce ammonia (NH3). If 4.4 liters of ammonia are produced at STP, how many grams of hydrogen reacted? (ans: 0.59g H2) N2(g) 4.4 L NH3 1 mol NH3 22.4 L NH3 + 3H2 → 2 NH3(g) 3 mol H2 2 mol NH3 2g H2 1 mol H2 = 0.59g H2 6. Use collision theory to explain the effect of each factor below on the rate of a chemical reaction: a. temperature: An increase in temperature results in an increase in average kinetic energy of reactants. This means there will be an increase in the number of successful collisions between reactants and an increase in the rate of reaction. b. surface area: an increase in surface area means more reactant molecules are exposed to collisions which increases the number of successful collisions, increasing the rate of reaction. c. stirring: means there is an increase in the probability that reactants will collide successfully more frequently, increasing the rate of reaction. d. adding a catalyst: Activation energy, which is the minimum amount of energy reactant particles require for successful collisions, is decreased by the addition of a catalyst. Catalysts decrease the activation energy by orienting reactant molecules for successful reactions. This leads to an increase in the rate of reaction. 7. What are the three components to the kinetic theory (for gases)? 1. The particles in a gas are assumed to be small, hard spheres with an insignificant volume. 2. The motion of particles in a gas is rapid and random. 3. All collisions between gas particles and the walls of the container they are in are perfectly elastic. 8. Use the phase diagram below to identify: a) the triple point b) the normal boiling point c) the state of the substance at 0.5atm and 25°C and d) the change that occurs as the substance is heated from 25°C to 100ºC at 0.5atm. a) b) c) d) 1 atm At point A ~100°C Solid sublimation A 0.5atm 25 50 75 ºCelsius 100 9. List 2 ways water could be made to boil at 105°C: a. ____add solute particles to the water (colligavtive properties)____________________ b. ___increase atmospheric pressure____________________________________________ 10. Pressure and volume of a gas at constant temperature are inversely proportional. If the volume of a gas triples, its pressure will decrease by one third 11. Volume and temperature of a gas at constant pressure are directly proportional. If the volume of a gas triples, its temperature will triple 12. Pressure and temperature of a gas at constant volume are directly proportional. If the temperature of a gas triples, the pressure will triple 13. If two containers are at the same temperature and pressure and their volumes are equal, they must contain the same number of particles 14. Molecules of oxygen gas and nitrogen gas are at the same temperature in equal sized flasks. Which molecules are moving faster? Nitrogen since one N2 molecule is lighter than one O2 molecule (N2 has a molar mass of 28g/mol and O2 has a molar mass of 32 g/mol) 15. If the oxygen gas molecules and nitrogen gas molecules in the scenario above are all at the same temperature, which gas has the greatest average kinetic energy? Neither - temperature is a measure of average kinetic energy, and the temperature for both substances is the same 16. A balloon is filled with 3.0 L of helium at 1 atm. What is the volume of the balloon when the pressure is only 0.25 atm? (ans: 12L) Hint: Formula: P1 V1= P2V2 (1 atm)(3.0L)= (0.25atm)(x) x= 12L 17. The gas left in a used aerosol can is at a pressure of 3.4 atm at 27.0C. If this can is thrown into a fire, what is the pressure of the gas when its temperature reaches 500.0C? (ans: 8.8 atm) Hint: Formula: P1 = P2 T1 T2 3.4 atm = P2 300 K 773 K = 8.8ATM 18. 5.2 L of a gas is at STP. Find the new volume when the temperature rises to 38C and the pressure drops to 600.0 mmHg. (ans: 7.5L) Hint: Formula: P1V1 = P2V2 T1 T2 (760mmHg)(5.2L) = (600mmHg)(V2) 273K 311K 19. Find the volume occupied by 14.0g of carbon dioxide at 25ºC and 0.880atm. Hint: Formula: PV = nRT 14.0g CO2 1 mol CO2 = 0.32 mol CO2 44g CO2 0.88atm (V) = 0.32mol(0.0821)(298K) V = 8.84 L = 7.5L (ans: 8.84L) 20. Find the molar mass of a gas if 3.0g of the gas occupy 1.7L at 25°C and 780mmHg. Hint: Formula: PV = nRT (ans: 42g/mol) (780mmHg) (1.7L)= n ( 62.4 ) (298K) n= .07mol Molar Mass= 3.0g = 42 g/mol .07mol 21. Find the density of Xenon gas at STP. (ans: 5.9g/L) Hint: Formula: PV=nRT (1atm) (1L) = n (0.0821)(273) n=0.0446 0.0446 moles 131.3g 1 mole = 5.9 g/1L 22. Determine the volume of oxygen gas that required for the complete combustion of 25.0g of methane gas (CH4) at 23°C and 99kPa. (ans: 78L) RXN: ___CH4 + 2 O2 CO2 + 2 H2O _________________________________________________ 25g CH4 1 mol CH4 16g CH4 2 mol O2 1 mol CH4 = 3.125 mol PV = nRT 99 kPa (V) = 3.125mol (8.31) (298 K) V = 78L 23. Complete the table below describing the solubility of each solute. SOLUTE CBr4 KBr CH2O SiO2 Soluble in gasoline? Y N N N Soluble in alcohol? N N Y N Soluble in water? N Y Y N 24. Define hydrogen bonding: A hydrogen bond is the electromagnetic attractive interaction between polar molecules in which hydrogen is bound to a highly electronegative atom, such as nitrogen, oxygen or fluorine 26. Circle each of the molecules below that would exhibit hydrogen bonding: (Hint: you will need to draw structure) a. HF b. CH2O c. NH3 d. CH4 e. H2 26. List four properties of water that are influenced by its strong hydrogen bonds. a. high surface tension: Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force caused by cohesion b. high specific heat capacity (absorbs a lot of heat as it warms up): amount of heat required to change the temperature of an object or body by a given amount c. cohesive forces: tendency of similar or identical particles/surfaces to cling to one another; hydrogen bonds increase cohesiveness of water d. density: solid water (ice) floats on liquid water; as water freezes, it becomes less dense e. strong adhesive forces: water molecules have a strong attraction to other water molecules 27. Use the graph to answer the questions below: a. How many grams of KClO3 need to dissolve in 50 g of water in order to have a saturated solution at 70C? ___15g _________ b. Which substance is the most soluble in water at 0C? ___ NH3__________ c. Which substance is least affected by temperature change? ____ NaCl _________ d. Which substance is the least soluble in water at 0C? ___ KClO3___________ e. Which substance becomes less soluble as the temperature increases? __ HCl, NH3__________ f. How would you describe the level of saturation of a solution of KNO3 at 40C if there are about 60g of KNO3 in 100g of water? ___ unsaturated _________ 28. Define “colligative property”: Colligative properties are properties that depend only on the # of solute particles (concentration of the solute), and not the nature of the solute or solvent. 29. Describe the effect that a solute has on the boiling point, freezing point and vapor pressure of the solvent: boiling point – is elevated, compared to pure solvent freezing point – is lowered, compared to pure solvent vapor pressure – lowers, compared to pure solvent 30. Fill in the blanks of the following paragraph: Word bank: pressure, temperature, concentration, high, low, solvent, solute Molarity, molality, percent by mass and volume express concentration of a solution. In order to dilute a solution more of a solvent can be added. In order to make more concentrated solution more of a solute can be added. Gases are most soluble in liquids under conditions of high pressure and low temperature. 31. Determine the molarity of a solution prepared by dissolving 15.0g of KCl in 525ml of water. Hint: Formula: : M = mol solute L solution M= . 201mol = 0.383M .525 L 15 g KCl 1mol KCl = .201 mol 74.5g (ans: 0.383M) 32. How many grams of KCl are needed to prepare a 0.25 liters of a 3.0 M solution? (ans: 56g KCl) Hint: Rewrite the molarity as: M = mol solute L solution .25L 3 mol 1L 74.6g 1mol = 56g 33. What volume of 4.0M KCl solution is needed to prepare 750.0mL of a 0.33M solution? What volume of water would also be needed? (ans: 62mL KCl solution, 688mL H2O) Hint: Formula: M1V1 = M2V2 4.0M (V) = 0.33M (750.0mL) V = 62mL 750mL-61.9mL = 688 mL H2O 34. What volume of 2.5M hydrochloric acid is needed to react with 32.5g of aluminum? (ans: 1.4L) RXN: _____6 HCl + 2 Al 2 AlCl3 + 3 H2______________________________________________ 32.5g Al 35. 1 mol Al 27.0g Al 6 mol HCl 2 mol Al 1L HCl 2.5 mol HCl = 1.4L What volume of isopropyl alcohol is in 325mL of a 75.0% isopropyl alcohol/water solution? (ans: 244mL) 75 mL iso 100 mL solution = x 325 mL solution X = 244mL 36. Find the mass percent of sodium chloride in a mixture containing 45.0g of sodium chloride in 255g of water. (ans: 15.0%) 45g solute 300g soltuion x 100 = 15.0% 37. Write dissociation equations and determine value of “i” for the following ionic compounds: a. KCl_____ K1+ + Cl1- ___________________________________________ i = ___2___ b. Na2SO4 ____2Na1+ + SO42- _____________________________________ i = __3____ c. the value of “ i” for molecular compounds such as C6H12O6 is ____1________ 38. Determine the boiling point of a solution prepared by dissolving 40.0g of potassium nitrate in 300.0g of water. (kf for water = 1.86°C/m, kb = 0.512°C/m) a. Find the molality of the solution: (ans: 1.32m) molality = moles KNO3 kg H20 40 g KNO3 x 1 mol KNO3 = 0.4 mol KNO3 101.1 g KNO3 b. The value for “i” is_____2______ c. Solve for ΔTb: molality = moles KNO3 = 0.4 mol KNO3 = 1.32m kg H20 0.300 kg ΔTb = kb • m • i = (0.512°C/m)(1.32m)(2) = 1.35 °C d. Find the boiling point: (ans: 101.36°C) 100°C + 1.35 °C = 101.35 °C e. How would the problem be solved if you were looking for the freezing point of the solution? Differences are bolded: ΔTf = kf • m • i = (1.86°C/m) (1.32m)(2) = 4.91 °C, so 0°C – 4.91 °C = -4.91 °C 39. What is the difference (in terms of energy) between water at 100C and steam at 100C? Steam at 100°C and water at 100°C have the same average kinetic energy (they are at the same temperature), but steam has much more potential energy than water at the same temperature. 40. Exothermic reactions release (absorb/ release) heat; endothermic reactions absorb (absorb/ release) heat. 41. A student is heating up sodium carbonate in order to decompose it according to following reaction: Na2CO3 (s) Na2O (s) + CO2 (g) Predict signs of ∆ H and ∆S for this process. ∆ H = __+___ ∆ S = _+____ Under what temperature conditions will this reaction be spontaneous? Only @ high temperature 42. Predict signs of ∆S for each process: a. NaCl (s) Na+(aq) + Cl- (aq). ∆ S = __+___ b. FeCl2(aq) + H2SO4(aq) FeSO4(s) + HCl(aq) ∆ S = _-____ c. ∆ S = __+___ Salt dissolving in water d. Condensation forming on the outside of a cold glass of water ∆ S = _-____ 43. Predict the amount of heat liberated when 25.0g of potassium chlorate decomposes, based on the reaction below: (ans: 9.11kJ) 2 KClO3 2 KCl 25 g KClO3 ∆ H = - 89.4kJ + 3 O2 1mol KClO3 89.4 kJ 122.6 g 2 mol KClO3 = 9.1 kJ 44. The data below refers to substance X. Melting Boiling Heat of Heat of Specific Heat point Point Fusion Vaporization Capacity (solid) Specific Heat Capacity (liquid) Specific Heat Capacity (vapor) 2.0°C 1.6 J/gºC 0.55 J/gºC 52.5C 275 J/g 1240 J/g 0.90 J/gºC a. Draw a heating curve for substance X, going from -10ºC to 70ºC on the axis below. Write in all formulas used to calculate heat. Label the phase present at each stage of your graph. Also label changes in potential and kinetic energy. 70°C Δ P. E. G Δ K. E. H= m Sh ▲T H= m Hv 52.5° C Δ P. E. L H= m Hf Δ K. E. H= m Sh ▲T 2°C S Δ K. E. H= m Sh ▲T -10°C a.. Calculate the amount of heat needed to raise the temperature of 15g of this substance from 54.0°C to 67.3°C. (ans: 109.7J) H =m(sh)(ΔT) H= ( 15g ) (0.55 J/gºC) (13.3°C) = 109.7 J b. What mass of X can be heated from 20.0°C to 35.0°C using 4000J of heat. (ans: 166.7g X) H =m(sh)(ΔT) 4000J = m (1.6 J/gºC) (15°C) m = 166.7 g c. What amount of heat will be given off if 25.5g of X are cooled from 12.0°C to -5.00°C? STEP 1: H =m(sh)(ΔT) H= (25.5g) (1.6 J/g ºC) (2°C -12°C) = -408 J STEP 2: H = mHf H= (25.5g) (275 J/g) = -7010 J STEP 3: H =m(sh)(ΔT) H= (25.5g) (0.90 J/gºC) (-5°C - -2°C)= -161 J TOTAL: -408 J + -7012.5 J + -160.7 J = -7580 J (ans: -7580J) 45. The specific heat of aluminum is 0.910J/gºC. A student heats a sample of aluminum to 123°C and places it in a calorimeter containing 150. g of water at 23.0ºC. The final temperature of the system is 43.0ºC. What was the mass of the aluminum sample? (ans: 172g) Mass specific heat Ti Tf ∆T METAL X 0.91 J/g°C 123 °C 43 °C -80 °C WATER 150 g 4.18 J/g°C 23 °C 43 °C 20 °C m(sh)(ΔT) = m(sh)(ΔT) (X)(0.91 J/g°C)(80 °C) = (150g)(4.18 J/g°C)(20°C) X = 172g 46. Equal mass of each substance below absorbs 1000J of heat, which would become the hottest? Why? Substance Specific Heat Capacity aluminum 0.897 J/g°C iron 0.454 J/g°C lead 0.130 J/g°C Lowest specific heat capacities heat up fastest 47. Given the diagram below, determine the: (include units) a. Enthalpy of the reactants_____100kJ __________ b. Enthalpy of the products_____300kJ __________ c. Heat of the reaction, ΔH. ____300-100 = +200kJ ____________ d. Activation energy of the reaction. ___400- 100= 300kJ __________ e. Exothermic or Endothermic? . ___ Endothermic (energy of product higher than energy of reactant)________________ 48. What is the pH of a solution that has a concentration of [H+] = 1.0 X 10-6M? ___6_____ Is this solution acidic, basic, or neutral? ____ acidic _______________ 49. What is the pH of a solution that has a concentration of [OH-] = 1.0 X 10-13M? ___1______ Is this solution acidic, basic, or neutral? ____ acidic _______________ 50. Complete the following table: Property Definition Taste Acids Produce H+ ions in solution with water, or donate H+ ions Sour Bases Produce OH- ions in solution with water, or accept H+ ions Bitter Touch Not slippery slippery Reaction with metals Produce H2 gas No reaction Electrical conductivity Yes yes Reaction with indicators (Phenolphthalein & litmus) 2 examples of strong Litmus BR Phenolphthalein: clear HCl, H2SO4 Litmus R B Phenolphthalein: pink NaOH, KOH 51. If 25 mL of 1.5 M of HCl is required to completely neutralize 35 mL of NH4OH, what is the concentration of the ammonium hydroxide? (ans: 1.1M) (#H+acid name)(M acid)(Volume acid) = (#OH-base name)(M base)(Volumebase) (1)(1.5M)(25ml) = (1)(X)(35ml) X = (1)(1.5M)(25ml) = 1.1M (1)(35ml) 52. How many mL of 0.5 M NaOH is needed to neutralize 16 mL of a 0.35 M H2SO4? (#H+acid name)(M acid)(Volume acid) = (#OH-base name)(M base)(Volumebase) (2)(0.35M)(16ml) = (1)(0.5M)(X) X = (2)(0.35M)(16ml) = 22.4 mL (1)(0.5M) (ans: 22.4mL) 53. Find the molar mass and percent composition (% of each element) for calcium nitrate. 1 Ca 2N 6O = 1 (40.1) = 2 (14.01) = 6 (16) = 40.1 = 28.02 = 96 164.12 40/164 *100 = 24.39 % 28.02/164 *100 = 17.07 % 96/164 *100 = 58.54 % % Ca _24.4%_____ %N _17.1%_______ % O _58.5%_______ 54. Find the mass of 1.50 moles of dicarbon tetrachloride. 249.0 g C2Cl4 1.50 moles 166 g 1 mole 55. How many molecules are in 14.0 g of dicarbon tetrachloride. 14.0 g 1 mole 166 g 6.02 x 1023 molecules 1 mole 5.08 x 1022 molecules C2Cl4 56. Write the empirical formula for dicarbon tetrachloride.______ CCl2______________ 57. A student does a lab to determine the molar mass of barium chloride. In lab, he determines the mass to be 216.0 g/mol. Find his percent error. 3.70% BaCl2 = (1 x 137.3) + (2 x 35.5) = 208.3 g/mol (actual) Percent error = experimental value - actual value actual value Percent error = 216.0 - 208.3 x 100% = 3.56% 208.3 x 100% = 3.56% 58. Identify and give the use for each piece of lab equipment below: watch glass- to hold solids while being weighed, or as a cover for a beaker or evaporating dish beaker tongs – used to transport a hot beaker iron ring and a ring stand- to support the evaporating dish – used to evaporate liquids laboratory apparatus (ex: while heating solvent) Erlenmeyer flask- are used in chemistry labs for titration ; they are useful in the lab setting for stirring the contents by hand by swirling the flask, as the tapered neck prevents spillage of the contents. Crucible tongs -used to grasp and take a Test tube holders – holds test tubes when heating Test tube clamp – used to clamp equipment to a ring stand hot crucible out of a fire or to move a crucible from one location to another. 59. Read each piece of lab equipment below: buret ____6.63________ mL graduated cylinder Thermometer ____21.5________ mL ______17___________ °C