Chemistry Final Exam Study Guide

Chemistry Final Exam Study Guide Mole Conversions 1 mole = 6.02 x 1023 particles 1 mole = molar mass (in grams) 1 mole = 22.4 L for any gas at STP 1. How many moles are in 9.0𝑥1024 xenon atoms? 𝟗. 𝟎𝒙𝟏𝟎𝟐𝟒 xenon atoms (𝟏𝒎𝒐𝒍/𝟔. 𝟎𝟐𝒙𝟏𝟎𝟐𝟒 atoms) = 15.0 mol 2 How many grams are in 15.5 moles of CO2? 15.5 moles 𝑪𝑶𝟐 (44g 𝑪𝑶𝟐 / 1 mol) = 682 g 3. What is the molar mass of (NH4)2O? 52 g/mol 4. The volume of 1 mole of a substance is 22.4 L for all gases 5. How many carbon atoms are in 5.8 grams of carbon? 5.8 g C (1 mol C/ 12 g)(6.02 x 𝟏𝟎𝟐𝟒 atoms/1 mol) = 2.9 x 𝟏𝟎𝟐𝟑 atoms 6. How many water molecules are there in 2.8 moles of water? 2.8 mol 𝑯𝟐 𝑶 ( 6.02 x 𝟏𝟎𝟐𝟑 molecules/ 1 mol) = 1.7 x 𝟏𝟎𝟐𝟒 molecules 7. How many moles are there in 53 L of oxygen gas? 53 L 𝑶𝟐 (1 mol/22.4 L) = 2.4 mol 0 ℃ and 8. STP for all gases is defined as 1 atm. 9. What is the percent (by mass) of oxygen in glucose (𝐶6 𝐻12 𝑂6 ) % = mass Oxygen/mass of glucose x 100 = 𝟗𝟔𝒈(𝟔𝑶’𝒔)/𝟏𝟖𝟎𝒈(𝑪𝟔 𝑯𝟏𝟐 𝑶𝟔 )𝒙𝟏𝟎𝟎 = 𝟓𝟑. 𝟑% Chemical Equations (chapters 11, 18) Balance these equations 10. NaOH + HCl → 11. Pb(NO3)2 + H2O + K2CrO4 → NaCl (it’s balanced!) PbCrO4 + 2 KNO3 12. C3H8 + 5 O2 → 3 CO2 + 4 H2O 13. In the above equation, O2 is a (product/ reactant/ catalyst) 14. What does this symbol (⇔) represent in a chemical equation? It’s a reversible reaction 15. Chemical equations must be balanced to satisfy which law? Law of Conservation of Mass (16-19) What type of reaction? (single replacement, double replacement, combustion, combination, decomposition) 16. 2 H2 + O2 → 17. Ca 18. 2 C4H10 + + 2 HCl → 2 H2O Combination CaCl2 + H2 Single replacement 13 O2 → 8 CO2 + 10 H2O Combustion Gases and States of Matter (chapters 13, 14) 19. What instrument is used to measure atmospheric pressure? Barometer 20. Collisions between molecules of a gas are (perfectly elastic, inelastic, cause a loss of kinetic energy) 21. What is the SI unit of pressure? Pascal 22. -273 The theoretical temperature at which the motion of all particles stops is ℃ (absolute zero) 0 23. What happens to the average kinetic energy of a substance as its temperature increases? Increases 24. Which particles are the first to evaporate from a liquid? Those at the surface that have enough kinetic energy 25. Which one will evaporate the fastest? Water at (5℃, 25℃, or 55℃) 26. What happens to the temperature of a boiling liquid if energy is added to it? It’s temp does not change 27. How could water be made to boil at 108℃ instead of 100℃? Kelvin or Increase the pressure above the liquid 28. Which one describes the particles in a piece of steel? (none are moving, some are moving, all are moving) Gas Laws Know how changing P/T/V conditions affect each other 𝑃1 𝑉1 = 𝑃2 𝑉2 𝑃1 /𝑇1 = 𝑃2 /𝑇2 𝑉1 /𝑇1 = 𝑉2 /𝑇2 Combined Gas Law = 𝑃1 𝑉1 /𝑇1 = 𝑃2 𝑉2 /𝑇2 29. If the volume of a gas-filled balloon is increased, what happens to its pressure? It decreases 30. If the temperature of a gas in a balloon is decreased, what happens to its volume? It decreases 31. If the temperature of a rigid container of gas is increased, what happens to its pressure? It increases 32. If 2 moles of gas are added to a container that already holds 1 mole of gas, what happens to the pressure? (it decreases, it doubles, it triples, it increases 4 times greater) 33. The volume of a gas increases from 1.5 L to 6.0 L How does the pressure change? It decreases by 4x (the volume increased by 4x) 34. A gas occupies a volume of 6.5 L at 3.3 kPa. What volume will it occupy at 14.7 kPa? 𝑃1 𝑉1 = 𝑃2 𝑉2 (3.3 kPa)(6.5 L) = (14.7 kPa) 𝑉2 35. 𝑉2 = 1.5 L A gas occupies 9 mL at -210 ℃. What volume will it occupy at 30℃? (Use Kelvin temp!) (in Kelvins, 𝑇1 = -210 + 273 = 63K and T2 = 30 + 273 = 303K) 𝑉1 /𝑇1 = 𝑉2 /𝑇2 9 mL/ 63K = 𝑉2 /303K 36. 𝑉2 = 43.3 mL The combined gas law relates which of the gas variables? Pressure, Temp, and Volume Water and Solutions (chapters 15,16) Molarity (M) = moles solute/ liters of solution 37. How does the surface tension of water compare to most other liquids? It is greater 38. What kind of bonds account for the surface tension of water? Hydrogen bonds 39. What kind of bonds hold oxygen to hydrogen atoms in water? (polar) covalent bonds 40. What does the dissolving in a solution? (solute or solvent?) 41. Can the parts of a solution be separated by filtering? No. They are too small 42. Water is a (polar/ nonpolar) molecule. 43. Which one will dissolve in water? (NH3 = polar covalent or C8H18 = nonpolar covalent) “k=like dissolves like” 43 Which substance is NOT an electrolyte? (NaCl, CCl4, HCl (a strong acid)) CCl4 is covalent (made of 2 non-metals) NaCl is ionic (metal-nonmetal) Good electrolytes = ionic compounds, acids, bases 44. What is the maximum amount of KCl that can dissolve in 50 g of water? (The solubility of KCl is 34 g/100 g H2O) 17 grams (half the amount that dissolves in 100 grams) 45. What is the molarity of a solution that contains 9 moles of solute in 4 liters of solution? Molarity = moles/L sol’n = 9 mol/4 L = 2.25 M 46. What type of substance is always an electrolyte? (covalent, ionic, network solid) 47. What is the molarity of a solution containing 5 moles of solute in 535 mL of solution? Molarity = 5 mol/ 0.535 L = 9.3 M 48. How many moles of solute are in 240 mL of a 0.5 M solution? Molarity = moles/Liters… so, moles = Molarity x Liters = 0.5 M x 240 L = 120 moles Thermochemistry (chapter 17) Q = mc△T Q = heat (in Joules or calories) m = mass (in grams) c = specific heat (in J/g℃ or cal/g℃) △T = change in temperature (in ℃) 49. How does a calorie compare to a Joule? (1 cal = 4.18 J) A calorie is bigger 50. What would you feel if you touched a flask in which an endothermic reaction were taking place? It would feel cold 51. If heat is absorbed by a system, an equal amount of heat will be released by the surroundings. 52. How many calories are in 9844 joules? (1 cal = 4.18 J) 9844 J ( 1 cal/ 4.18 J) = 2,355 cal 53. How much heat is needed to raise the temperature of 300 grams of mercury from 12℃ to 22℃? (the specific heat of mercury is 0.033 cal/g℃) (use Q = mc△T) Q = mc△T = 300 g x 0.033 cal/g ℃ x 10℃ = 99 cal 54. During a phase change, the temperature of a substance does NOT change. 55. Activation energy is The energy needed to get from reactants to products . 56. Which of these act as catalysts in the human body? (carbohydrates, nucleic acids, enzymes, lipids) 57. A catalyst works by lowering the activation energy! 58. At equilibrium, what is the rate of production of products compared to the rate of production of reactants? (the same, much higher, much lower) 59. Name 5 changes that will shift the following reaction to the right: 𝐶(𝑆) + 𝐻2 𝑂(𝑔) + ℎ𝑒𝑎𝑡 ⇔ 𝐶𝑂(𝑔) + 𝐻2(𝑔) Add C, add H2O, add heat, remove CO, remove H2, decrease pressure (1 mol of gas on the left, 2 moles gas on the right, add catalyst? 60. What is the effect of decreasing the pressure on this reaction? 𝟐𝑺𝑶𝟐(𝒈) + 𝑶𝟐(𝒈) ⇔ 𝟐𝑺𝑶𝟑(𝒈) + 𝒉𝒆𝒂𝒕 Shifts to the left (3 moles of gas on left, 2 moles on right) 61. The amount of heat required to raise 1 gram of water by 1℃ is . (calorie, joule, specific heat, density) 62. The amount of heat required to raise 1 gram of a substance by 1℃ is . (calorie, joule, specific heat, density) 63. What is the specific heat of a substance if 3200 calories are required to raise the temperature of a 290 gram sample by 38℃? (use Q = mc△T) c = Q/m△T = 3200 cal/ 290 g x 38℃ = 0.29 cal/g ℃ 64. How much heat would be released by a piece of candy that contained 2500 calories if it was burned completely? 2500 cal Acids and Bases (chapter 19) 65. Which one(s) are properties of acids? (bitter taste, pH values above 7, unreactive, electrolytes) 66. What are the products of combining an acid and a base? water 67. and a salt 𝑯+ What is the formula for the hydrogen ion? Formula for the hydronium ion = Hydroxide ion = 68. . OH- 𝑯𝟑 O+ . . . What type of solution has a pH of 6? A weak acid 69. Which of these is the strongest acid? pH = 3.2, pH = 7.2, pH = 13.3, pH = 3.5 Atomic Structure/ Scientific Measurement (chapters 3 and 4) 70. The distance from Earth to the sun is 150,000,000 km. What is this number expressed in scientific notation? 1.5 x 108 km 71. The diameter of a copper atom is 1.45 x 10-10 m. What is this number in standard notation? 0.000 000 000 145 m 72. Which temperature scale has no negative numbers? kelvin scale 73. What is the freezing point of water in kelvins? ℃ + 273 = kelvins 74. 0℃ + 273 = 273K What is -198℃ expressed in kelvins? -198 + 273 = 75K 75. Which particles are found in the nucleus of an atom? protons and neutrons 76. The atomic number of an element is equal to which particle in the nucleus? proton 77. Name the three subatomic particles, give their charges, and masses. proton = + charge, 78. neutron = no charge, electron = - charge What does the number in cesium-133 represent? the mass number (the number of protons and neutrons in nucleus) 79. All atoms of the same element have the same number of protons 80. Isotopes of the same element have different numbers of neutrons