Given standard enthalpies of formation CH₄(g) = −74.8, CO₂(g) = −393.5 and H₂O(l) = −285.8 kJ mol⁻¹, what is ΔH for CH₄ + 2O₂ → CO₂ + 2H₂O(l)?
Correct answer B. −890.3 kJ mol⁻¹
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Thermochemistry and Energetics MCQs
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- Gases 40
- Liquids 40
- Solids 40
- Chemical Equilibrium 40
- Reaction Kinetics 40
- Thermochemistry and Energetics 40
- Electrochemistry 40
- Fundamental Concepts of Chemistry 40
- Atomic Structure 39
- Chemical Bonding 39
- Alcohols and Phenols 38
- Industrial Chemistry 37
- Aldehydes and Ketones 37
- Alkyl Halides 37
- s- and p-Block Elements 37
- Chemistry of Hydrocarbons 36
- Fundamental Principles of Organic Chemistry 36
- Carboxylic Acids 36
- Transition Elements 35
- Macromolecules 35
What is the standard enthalpy of formation of O₂(g) at 298 K?
Correct answer B. 0 kJ mol⁻¹
Which statement best defines the standard enthalpy of combustion of a substance?
Correct answer D. The enthalpy change when one mole of the substance burns completely in excess oxygen under standard conditions
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Why is the enthalpy of neutralisation of ethanoic acid by NaOH less negative than that of HCl by NaOH?
Correct answer B. Some energy is used to ionise the weak acid fully
When a reaction is carried out in 50.0 g of water, the temperature rises by 6.0 °C. Taking c = 4.18 J g⁻¹ K⁻¹, how much heat is released?
Correct answer B. 1254 J
Using bond energies H–H = 436, Cl–Cl = 243 and H–Cl = 432 kJ mol⁻¹, what is ΔH for H₂(g) + Cl₂(g) → 2HCl(g)?
Correct answer C. −185 kJ mol⁻¹
How is the lattice energy of an ionic compound such as NaCl usually obtained?
Correct answer C. Indirectly, from a Born-Haber cycle using Hess's law
What is meant by the heat capacity of a body?
Correct answer D. The heat required to raise its temperature by 1 K
Which statement about the internal energy, U, of a system is correct?
Correct answer C. It is the total kinetic and potential energy of its particles, and only changes in it can be measured
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When a gas in a cylinder is compressed by a piston, what are the signs of the work done (w) and its effect on the internal energy of the gas, if no heat is exchanged?
Correct answer D. w is positive and internal energy increases
Which statement is true for an exothermic reaction?
Correct answer C. ΔH is negative and heat is released to the surroundings
Given C(s) + O₂(g) → CO₂(g), ΔH = −393.5 kJ mol⁻¹ and CO(g) + ½O₂(g) → CO₂(g), ΔH = −283.0 kJ mol⁻¹, what is ΔH for C(s) + ½O₂(g) → CO(g)?
Correct answer B. −110.5 kJ mol⁻¹
Which statement is Hess’s law?
Correct answer A. The total enthalpy change of a reaction is the same whatever route is taken, provided the initial and final states are the same
In a bomb calorimeter the reaction takes place in a sealed steel vessel. Which quantity does the heat measured correspond to directly?
Correct answer A. ΔU, the change in internal energy
Under what condition is the heat exchanged in a reaction equal to its enthalpy change, ΔH?
Correct answer B. At constant pressure
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A system absorbs 250 J of heat and does 100 J of work on the surroundings. What is the change in its internal energy?
Correct answer B. +150 J
Which equation expresses the first law of thermodynamics, using the convention that work done on the system is positive?
Correct answer D. ΔU = q + w
An ideal sealed vacuum flask allows neither heat nor matter to cross its walls. What kind of system does its contents represent?
Correct answer C. Isolated system
Which of the following is a state function?
Correct answer B. Enthalpy
Which of the following processes is endothermic?
Correct answer B. Thermal decomposition of calcium carbonate