All Free Chemistry MCQs with Answers
Every Chemistry question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
13,720 questions · page 509 of 686
- A. Has more internal energy
- B. Has less internal energy
- C. Has the same internal energy
- D. None of these
Explanation: The internal energy of a substance is dependent on its temperature, pressure, and phase, not on the path taken to reach that state.
Correct answer: Has the same internal energy- A. +250 kJ
- B. -250 kJ
- C. +750 kJ
- D. -750 kJ
Explanation: According to the first law of thermodynamics, the change in internal energy (ΔU) is equal to the heat added to the system (q) minus the…
Correct answer: -750 kJ- A. 1 J/g°C
- B. 0.5 J/g°C
- C. 2 J/g°C
- D. None of the above
Explanation: The specific heat capacity (c) is calculated using the formula Q = mcΔT.
Correct answer: 0.5 J/g°C- A. Glass
- B. Water
- C. They both will experience the same change in temperature since only the amount of substance relates to the increase in temperature
- D. None
Explanation: The correct answer is Glass. The specific heat capacity of a substance tells us how much energy is required to change the temperature of a…
Correct answer: Glass- A. -82 kJ
- B. -2050 kJ
- C. -24,600 kJ
- D. None
Explanation: To solve this question, first convert the mass of carbon to moles. The molar mass of carbon is approximately 12.01 g/mol.
Correct answer: -2050 kJ- A. -217 kJ/mole
- B. +217 kJ/mole
- C. -88.0 kJ/mole
- D. +88.0 kJ/mole
Explanation: To calculate the standard heat of reaction, use the formula ΔH°reaction = ΣΔH°f,products - ΣΔH°f,reactants.
Correct answer: -217 kJ/mole- A. The sign of ΔH is positive, and the products have less potential energy than the reactants.
- B. The sign of ΔH is positive, and the products have more potential energy than the reactants.
- C. The sign of ΔH is negative, and the products have less potential energy than the reactants.
- D. The sign of ΔH is negative, and the products have more potential energy than the reactants.
Explanation: In an endothermic reaction, energy is absorbed from the surroundings, which means the enthalpy change (ΔH) is positive.
Correct answer: The sign of ΔH is positive, and the products have more potential energy than the reactants.- A. -64
- B. +64
- C. -168
- D. +168
Explanation: To find the heat of formation of C₂H₄Cl₂(g), apply Hess's Law. First, reverse the second reaction to match the formation of C₂H₄Cl₂(g)…
Correct answer: +64- A. +81.5
- B. -81.5
- C. +163
- D. -163
Explanation: To find the ΔH° for the reaction N₂(g) + 1/2 O₂(g)→N₂O(g), we need to manipulate the given thermochemical equations using Hess's Law.
Correct answer: +81.5- A. +232.4 kJ
- B. +423.5 kJ
- C. +518.0 kJ
- D. +596 kJ
Explanation: To determine the heat of reaction, apply Hess's Law: ΔH°reaction = ΣΔH°f(products) - ΣΔH°f(reactants).First, identify the standard…
Correct answer: +596 kJ- A. -198.6 kJ
- B. +198.6 kJ
- C. +133.5 kJ
- D. -134 kJ
Explanation: To find the heat of reaction (ΔH°), apply the formula: ΔH° = ΣΔH°f (products) - ΣΔH°f (reactants).
Correct answer: -134 kJ- A. -1566 kJ
- B. -1285 kJ
- C. -1856 kJ
- D. -1790 kJ
Explanation: To determine the heat of reaction, use the formula: ΔH°rxn = ΣΔH°f(products) - ΣΔH°f(reactants).
Correct answer: -1790 kJ- A. -92 kJ/mol
- B. -55 kJ/mol
- C. -102 kJ/mol
- D. -121 kJ/mol
Explanation: The given reaction is CH2=CH2(g) + H2(g) → CH3-CH3(g). To find ΔH°f, calculate the total energy for breaking bonds (reactants) and forming…
Correct answer: -121 kJ/mol- A. Thermodynamics
- B. Thermochemistry
- C. Calorimetry
- D. None of the above
Explanation: Thermochemistry is the branch of physical chemistry that focuses on the study of heat changes that accompany chemical reactions.
Correct answer: Thermochemistry- A. Thermo chemistry
- B. Conductometry
- C. Thermodynamics
- D. None of the above
Explanation: The correct answer is Thermodynamics. It is a branch of physical science that deals with the relations between heat and other forms of…
Correct answer: Thermodynamics- A. It tells about the physical state of the reactants and products.
- B. It tells whether a reaction is exothermic or endothermic.
- C. It tells about the allotropic forms of the reactant.
- D. It tells whether a particular reaction is possible or not.
Explanation: The correct answer is Option B. A thermochemical reaction involves the study of energy changes, particularly heat, associated with…
Correct answer: It tells whether a reaction is exothermic or endothermic.- A. Takes place on heating.
- B. Is accompanied by a flame.
- C. Is accompanied by absorption of heat.
- D. Is accompanied by evolution of heat.
Explanation: In an exothermic reaction, energy is released to the surroundings in the form of heat.
Correct answer: Is accompanied by evolution of heat.- A. Heat is converted into electricity.
- B. Heat is absorbed.
- C. Heat is evolved.
- D. Heat is converted into mechanical work.
Explanation: In an endothermic reaction, the system takes in heat from its surroundings, resulting in a temperature decrease in the surroundings.
Correct answer: Heat is absorbed.- A. Have more energy than the products.
- B. Have less energy than the products.
- C. Have the same energy as the products.
- D. Are at a higher temperature than the products.
Explanation: In an exothermic reaction, the reactants have more stored chemical energy than the products.
Correct answer: Have more energy than the products.- A. CH4 + 2O2 → CO2 + 2H2O
- B. C+2S → CS2
- C. H2 + I2 → 2HI
- D. None of the above
Explanation: In an exothermic reaction, energy is released as heat. Option A involves the combustion of methane, which is a highly exothermic process.
Correct answer: CH4 + 2O2 → CO2 + 2H2O