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 503 of 686
10041. Liquid in the container has a temperature 70°C. What will be the temperature on the Kelvin scale?
- A. 350 K
- B. 343 K
- C. 300 K
- D. 283 K
Explanation: To convert temperature from celsius to kelvin scale the formula is: °C + 273.15 K 70° + 273.15 = 343 K Therefore, option b is correct.
Correct answer: 343 K- A. 3/2R
- B. 5/2R
- C. Dependent on the atomicity of the gas
- D. Infinity
Explanation: When a gas is at constant temperature and pressure, adding heat does not change the temperature, which means the heat capacity is…
Correct answer: Infinity- A. Endothermic
- B. Exothermic
- C. ∆H = 0
- D. None of the above
Explanation: The enthalpy of reaction is ΔH = ΣΔHf (products) - ΣΔHf (reactants). ΔH = [4(0) + 3(-393.7)] - [2(-824.2) + 3(0)] = -1181.1 + 1648.4 =…
Correct answer: Endothermic- A. 70.26 JK-1
- B. 82.55 JK-1
- C. 95.73 JK-1
- D. 107.11 JK-1
Explanation: To calculate the change in entropy of an ideal gas, we can use the formula:ΔS = nR ln(V2/V1)Given that 5 moles of an ideal gas expand…
Correct answer: 95.73 JK-1- A. Extensive property
- B. Colligative property
- C. Intensive property
- D. Constitutive property
Explanation: Standard heat of combustion is defined for a specific amount of substance (per mole).
Correct answer: Intensive property- A. 20 ml acid and 30 ml alkali
- B. 10 ml acid and 40 ml alkali
- C. 25 ml acid and 25 ml alkali
- D. 35 ml acid and 15 ml alkali
Explanation: The heat released is maximized when the maximum number of moles of acid and base react.
Correct answer: 25 ml acid and 25 ml alkali- A. ∆S > 0
- B. ∆S < 0
- C. ∆H < 0
- D. ∆G > 0
Explanation: As ∆G = ∆H - T∆SFor spontaneous process, ∆G = negative For endothermic process, ∆H = positive Therefore, ∆S > 0
Correct answer: ∆S > 0- A. Adiabatic expansion
- B. Adiabatic compression
- C. Both a and b
- D. None of these
Explanation: In an adiabatic expansion, the gas expands without heat exchange with the surroundings, leading to a decrease in internal energy and…
Correct answer: Adiabatic expansion- A. ΔH
- B. ΔE
- C. ΔV
- D. ΔH+ΔE
Explanation: The change in enthalpy (ΔH) of a system is defined as the heat transferred at constant pressure.
Correct answer: ΔH- A. Heat of reaction
- B. Heat of atomization
- C. Heat of formation
- D. Heat of combustion
Explanation: This is the precise definition of the standard enthalpy of combustion (ΔH°c ).
Correct answer: Heat of combustion- A. ΔHf (formation)
- B. ΔHc (combustion)
- C. ΔHsol (solution)
- D. Both A and C
Explanation: The enthalpy of formation (ΔHf) can be positive (endothermic) or negative (exothermic).
Correct answer: Both A and C- A. Spontaneous
- B. Exothermic
- C. Non-spontaneous
- D. Both A and B
Explanation: The reaction between a strong acid and a strong base is highly favorable, releasing a significant amount of heat (exothermic, ΔH < 0).
Correct answer: Both A and B- A. 0°C and 1 atm pressure
- B. 0 K and 1 atm pressure
- C. 25°C and 1 atm pressure
- D. 25°C and 2 atm pressure
Explanation: The symbol "°" denotes standard conditions in thermodynamics. For thermochemical data, this is almost universally defined as a pressure of…
Correct answer: 25°C and 1 atm pressure- A. ΔH=ΔU+PΔV
- B. ΔH=ΔU-ΔnRT
- C. ΔU=ΔH+ΔP
- D. ΔH=ΔU-PΔV
Explanation: This equation is the definition of enthalpy change (ΔH) at constant pressure.
Correct answer: ΔH=ΔU+PΔV- A. 1/2 I(sp)→ I(l)
- B. 1/2 I2(s)→I(g)
- C. I2(l)→2l(g)
- D. I2(g)→2l(g)
Explanation: The standard enthalpy of atomization of an element is the amount of heat absorbed when one mole of gaseous atoms are formed from the…
Correct answer: 1/2 I2(s)→I(g)- A. 273 K
- B. 373 K
- C. 298 K
- D. 473 K
Explanation: The standard enthalpy of formation, ΔH°f, is measured under standard conditions, which include a temperature of 25°C (298 K) and a…
Correct answer: 298 K- A. Enthalpy of solution
- B. Enthalpy of sublimation
- C. Enthalpy of neutralization
- D. Enthalpy of formation
Explanation: The reaction between an acid and a base to form a salt and water is an exothermic process, meaning it always releases heat.
Correct answer: Enthalpy of neutralization10058. Hess's law is known as:
- A. Law of heat summation
- B. Law of constant heat capacity
- C. Law of mass action
- D. Law of conservation of mass
Explanation: Hess's law of heat summation, also known as Hess's law, states that the enthalpy change for a chemical reaction is the same whether the…
Correct answer: Law of heat summation- A. Joule mol-1
- B. KJ mol-1
- C. Both A and B
- D. None of these
Explanation: The SI unit for energy change in a chemical reaction is joules per mole.
Correct answer: Both A and B- A. Surroundings
- B. Boundaries of the system
- C. Only within the system
- D. All of these
Explanation: Heat is the energy that flows across the boundaries of the system. This means that heat can flow into or out of the system, but it cannot…
Correct answer: Boundaries of the system