59. A sample of helium gas has a volume of 5.0 L at 27 °C and 1.0 atm. What will its volume be at 127 °C and 1.0 atm?

4. Which molecules are best explained by resonance in MO theory?

57. What is the molar concentration of OH⁻ in a solution with pOH = 4.0?

65. If a galvanic cell produces a current of 2.0 A for 1.0 hour, how many moles of electrons are transferred? (Faraday’s constant = 96,500 C/mol e⁻)

62. A first-order reaction has a half-life of 20 minutes. How long will it take for 75% of the reactant to decompose?

74. What is the pH of a 0.0010 M HNO₃ solution?

55. How many grams of KCl (molar mass = 74.5 g/mol) are needed to prepare 250 mL of a 2.0 M solution?

46. If 10.0 g of aluminum reacts with excess hydrochloric acid, how many liters of hydrogen gas are produced at STP? (Reaction: 2Al + 6HCl → 2AlCl₃ + 3H₂)

30. When 4.0 grams of hydrogen gas react completely with oxygen gas, how many grams of water are produced? (Reaction: 2H₂ + O₂ → 2H₂O)

54. What is the wavelength of light emitted when an electron in hydrogen falls from n = 3 to n = 2? (Rydberg constant R = 1.097×10⁷ m⁻¹)