An electron in a hydrogen atom transitions from n = 4 to n = 2. Using the Rydberg formula, the wavelength of the emitted photon is closest to: (R_H = 1.097 × 10⁷ m⁻¹)
General Chemistry
Question · Medium
Km or Vmax: an aria of rivals
Short
Which of the following correctly ranks the first ionization energies from lowest to highest? (I) Mg (II) Na (III) Al (IV) P
Question · Hard
Introduction
1.1 Exam Format, Scoring & the Two Foundational Concepts
Study guide
A solution is prepared by dissolving 4.0 g of NaOH (MW = 40 g/mol) in enough water to make 500 mL of solution. What is the pH of this solution?
Question · Easy
At constant temperature, 2.0 L of an ideal gas at 3.0 atm is compressed to 1.0 L. What is the new pressure?
The reaction A → B has ΔH° = −80 kJ/mol and ΔS° = −200 J/(mol·K). At what temperature (in K) does this reaction become non-spontaneous?
A buffer solution is made from acetic acid (pKa = 4.74) and sodium acetate. If [CH₃COOH] = 0.10 M and [CH₃COO⁻] = 0.20 M, what is the pH of the buffer?
1.2 Scientific Inquiry & Reasoning Skills (SIRS) and No-Calculator Rules
For the equilibrium N₂(g) + 3H₂(g) ⇌ 2NH₃(g), at a given temperature Kc = 0.50. If the initial concentrations are [N₂] = 1.0 M, [H₂] = 1.0 M, and [NH₃] = 0.0 M, which way will the reaction proceed?
Passage: In a galvanic cell, zinc is oxidized at the anode and copper ions are reduced at the cathode. Standard reduction potentials are: Zn²⁺/Zn = −0.76 V and Cu²⁺/Cu = +0.34 V. What is the standard cell potential (E°cell) for this galvanic cell?
Passage: In a galvanic cell, zinc is oxidized at the anode and copper ions are reduced at the cathode. Standard reduction potentials are: Zn²⁺/Zn = −0.76 V and Cu²⁺/Cu = +0.34 V. Using ΔG° = −nFE°, and given that n = 2 and F = 96,485 C/mol, what is ΔG° for this cell reaction (approximately)?
The rate law for a reaction is: rate = k[A]²[B]. If the concentration of A is doubled while B is held constant, how does the rate change?
Chapter 1: Translational Motion, Forces, Work & Energy
Units, Vectors & Translational Motion
Which of the following molecules is polar? (I) CO₂ (II) BF₃ (III) H₂O (IV) CCl₄
The van't Hoff factor (i) for 0.1 m NaCl (fully dissociated) in calculating boiling point elevation is:
A weak acid HA has Ka = 1.0 × 10⁻⁵. What is the pH of a 0.10 M solution of HA?
Passage: A chemist studies the rate of decomposition of H₂O₂: 2H₂O₂ → 2H₂O + O₂. She finds the reaction is first order with rate constant k = 0.023 min⁻¹ at 25°C. What is the half-life of H₂O₂ under these conditions?
Newton's Laws, Force & Friction
Passage: A chemist studies the rate of decomposition of H₂O₂: 2H₂O₂ → 2H₂O + O₂. She finds the reaction is first order with rate constant k = 0.023 min⁻¹ at 25°C. If the initial concentration of H₂O₂ is 0.80 M, approximately what concentration remains after 60 minutes?
Which of the following statements best describes the Aufbau principle?
Which of the following processes has a positive entropy change (ΔS > 0)?
Which of the following aqueous solutions has the highest boiling point? (All at 0.1 mol solute per kg water)
Equilibrium: Vector Analysis of Forces & Torque
In the reaction: CH₄ + 2O₂ → CO₂ + 2H₂O, what mass of CO₂ (MW = 44 g/mol) is produced when 32 g of CH₄ (MW = 16 g/mol) is completely combusted?
Which of the following correctly orders the bond lengths from shortest to longest? (Bond types: C–C single, C=C double, C≡C triple)
The reaction: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g) is exothermic. According to Le Chatelier's principle, which change will shift the equilibrium to the RIGHT?
Which element has the electron configuration [Ar] 3d¹⁰ 4s¹?
Work and the Work-Energy Theorem
A student measures the osmotic pressure of a 0.10 M protein solution at 37°C (310 K). Using π = MRT (R = 0.0821 L·atm/(mol·K)), what is the osmotic pressure?
In electrolysis of molten NaCl, which reaction occurs at the cathode?
Which of the following best explains why HF is a weak acid despite fluorine being the most electronegative element?
A car accelerates uniformly from rest to 30 m/s in 10 seconds. What distance does the car travel during this time?
Physics
Kinetic/Potential Energy, Conservation of Energy & Power
A 5.0 kg block slides down a frictionless incline angled at 30° to the horizontal. What is the acceleration of the block along the incline? (g = 10 m/s²)
A 2.0 kg object moving at 6.0 m/s collides with a stationary 4.0 kg object. After a perfectly inelastic collision, what is the velocity of the combined mass?
A spring with spring constant k = 400 N/m is compressed by 0.05 m. How much elastic potential energy is stored?
Blood flows through an artery with radius r₁ = 0.5 cm at velocity v₁ = 20 cm/s, then into an arteriole with radius r₂ = 0.1 cm. What is the velocity v₂ in the arteriole?
Periodic Motion: Amplitude, Frequency, Phase & Wave Types
Passage: Coronary artery stenosis reduces the lumen cross-sectional area to 25% of normal. Normal blood velocity = 0.2 m/s; blood density ρ = 1060 kg/m³. What is the blood velocity through the stenosis?
Passage: Coronary artery stenosis reduces the lumen cross-sectional area to 25% of normal. Normal blood velocity = 0.2 m/s; blood density ρ = 1060 kg/m³. Using Bernoulli's equation, what is the pressure drop across the stenosis?
A 70 kg person runs up a 10-meter-high staircase in 20 seconds. What is the average power output? (g = 10 m/s²)
Two positive point charges, +2 μC and +8 μC, are 0.30 m apart. At what distance from the +2 μC charge (along the line between them) is the net electric field zero?
Chapter 2: Fluids & Gas Phase
3.1 Fluid Statics: Density, Buoyancy & Hydrostatic Pressure
A sound wave has frequency 440 Hz and travels at 340 m/s in air. What is its wavelength?
A light ray travels from water (n = 1.33) into glass (n = 1.50) at an angle of incidence of 45°. What is the angle of refraction (approximately)?
A parallel-plate capacitor has plate area A = 0.02 m² and plate separation d = 0.002 m. What is its capacitance? (ε₀ = 8.85 × 10⁻¹² F/m)
In a simple circuit, a 12 V battery is connected to three resistors in series: R₁ = 2 Ω, R₂ = 4 Ω, R₃ = 6 Ω. What is the current in the circuit?
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