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All Free Chemistry MCQs with Answers

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13,720 questions · page 518 of 686

10341. The correct equation for the first law of thermodynamic is:

  • A. E = q + w
  • B. E = w-q
  • C. E = q -PV
  • D. E = q +PV

Explanation: Option A (E = q + w) is the correct equation because it accounts for both the heat added to the system (q) and the work done on or by the…

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Correct answer: E = q + w

10342. Why a reaction is reversible?

  • A. Reactants are reactive
  • B. Reactants are stable
  • C. Products are reactive
  • D. Products are stable

Explanation: The reversibility of a reaction is determined by the reactivity of the products.

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Correct answer: Products are reactive

10343. Volume is a:

  • A. Intensive property
  • B. Entropy
  • C. Path function
  • D. Isolated system
  • E. State function

Explanation: A s tate function is a property of a system that depends only on its current state, rather than the path taken to reach that state.

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Correct answer: State function

10344. An example of an endothermic reaction is:

  • A. Photosynthesis
  • B. Synthesis of NH3
  • C. Nuclear fission
  • D. Oxidation of sulfur gases
  • E. Burning of fuel and coal

Explanation: Photosynthesis is an endothermic process. During photosynthesis, plants absorb light energy from the sun and convert it into chemical…

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Correct answer: Photosynthesis

10345. In endothermic reaction,the heat content of the:

  • A. Reactants and products is equal
  • B. Reactants is more than that of products
  • C. Products is more than that of reactants
  • D. Reactants & Products will not change

Explanation: This is the correct statement. In endothermic reactions, the products have greater energy (or heat content) than the reactants because…

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Correct answer: Products is more than that of reactants

10346. All of the following steps are used to calculate the lattice energy in the Born-Haber cycle EXCEPT:

  • A. Atomizing the metal
  • B. lonizing the metal
  • C. Deionize the metal
  • D. lonize non metal

Explanation: Deionizing metal is not part of the Born-Haber cycle. It would involve turning ions back into atoms, which is not necessary for…

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Correct answer: Deionize the metal

10347. The enthalpy change when 1 Mole of water is formed by the reaction of acid with an alkali under standard conditions is known as:

  • A. Enthalpy of formation
  • B. Enthalpy of reaction
  • C. Enthalpy of combustion
  • D. Enthalpy of neutralization

Explanation: The enthalpy of neutralization is the specific enthalpy change when one mole of water is formed from the reaction of an acid and a base…

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Correct answer: Enthalpy of neutralization

10348. At constant volume, the heat supplied to a system is always equal to its

  • A. bond energy
  • B. enthalpy change
  • C. heat of sublimation
  • D. internal energy change

Explanation: At constant volume, the change in internal energy (ΔU) of a system can be expressed using the heat added to the system and the work done.

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Correct answer: internal energy change

10349. What will be the internal energy of a system at constant volume?

  • A. delta E =0
  • B. delta E = q+p
  • C. delta E = q+ PdeltaV
  • D. delta E = qv

Explanation: The equation ΔE=QV relates the change in internal energy (ΔE) of a system at constant volume to the heat added or removed from the system…

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Correct answer: delta E = qv

10350. Who stated that enthalpy change in a chemical reaction is same whether the reaction takes place in single step or in several steps?

  • A. Arrhenius' Law
  • B. Born Haber's Law
  • C. Dalton's Law
  • D. Hess's Law

Explanation: Hess's Law states that the total enthalpy change of a reaction is the same, regardless of the pathway taken.It allows you to find the…

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Correct answer: Hess's Law

10351. calculate the work done when 1 mole of an ideal gas expands from 15 dm3 to 20 dm3 against a constant external pressure of 2 atmospheres

  • A. -10 atm.dm3
  • B. -5 atm.dm3
  • C. 5 atm.dm3
  • D. 10 atm.dm3

Explanation: W=-PΔVΔV is 20-15 =5dm3 W=- 2atm x 5dm3 =-10atm.dm3

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Correct answer: -10 atm.dm3

10352. When 1 mole of ice melts at 0° and constant pressure of 1 atmosphere, 6025 J of heat is absorbed by the system. The molar volume of ice and water are 0.020and 0.018 dm3, respectively. Calculate ΔE.(1dm3.atm=101.33J)

  • A. 6010.20J
  • B. 6015.20J
  • C. 6020.20J
  • D. 6025.20J

Explanation: ΔE=q−PΔVΔV=Vwater −Vice =0.018dm3 −0.020dm3 =−0.002dm3PΔV=(1atm)×(−0.002dm)=−0.002dm3atmPΔV=−0.002dm3⋅atm×101.33J/(dm3⋅atm)=−0.20266JΔE=q−P…

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Correct answer: 6025.20J

10353. One slice of bread with a tablespoon of peanut butter on it contains 20g carbohydrate, 10g protein,and 9g fat. Calculate total energy consumed in this intake

  • A. 158kcal
  • B. 173kcal
  • C. 201kcal
  • D. 218kcal

Explanation: Energy from carbohydrates=20g×4kcal/g=80kcalEnergy from protein=10g×4kcal/g=40kcalEnergy from fat=9g×9kcal/g=81kcalTotal energy=Energy…

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Correct answer: 201kcal

10354. ΔH can be measured indirectly by applying

  • A. Avogadro's law
  • B. Faraday's Law
  • C. Gas's Law
  • D. Hess's Law

Explanation: Hess's Law states that the total enthalpy change during a chemical reaction is the same, regardless of whether the reaction occurs in one…

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Correct answer: Hess's Law

10355. The heat of sublimation of potassium is 98kJ/mol. The heat of dissociation of bromine gas is 192.5 kJ/mol. The ionization energy of K is 414 kJ/mol. The electron affinity of Br -334.7kJ/mol and the heat of formation of KBr is -405.8 kJ/mol. Calculate the lattice energy of KBr

  • A. -679.3
  • B. -669.5
  • C. 669.5
  • D. 679.3

Explanation: By applying Hess's lawΔHf=ΔHsubl+ΔHdiss+ΔHIE+ΔHEA+U (U is the lattice energy)The lattice energy of KBr is approximately 679.35 kJ/mol (the…

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Correct answer: -679.3

10356. Which of the following food product has lower energy per gram?

  • A. Milk
  • B. Ghee
  • C. Butter
  • D. Glucose

Explanation: Correct. Milk has a lower fat content compared to ghee and butter, and a lower carbohydrate content compared to glucose, resulting in…

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Correct answer: Milk

10357. The sign of heat "q" is positive for a system when:

  • A. The temperature of system drops
  • B. Heat flows from surrounding to system:
  • C. Heat flows from system to surrounding.
  • D. No flow of heat between system to surrounding

Explanation: This is the definition of an endothermic process. The system absorbs heat, so q is positive.

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Correct answer: Heat flows from surrounding to system:

10358. 5 calories are equivalent to _ Joule.

  • A. 4.184
  • B. 10.26
  • C. 20.92
  • D. 25.65

Explanation: 5 calories * 4.184 Joules/calorie = 20.92 Joules.

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Correct answer: 20.92

10359. Units of change in enthalpy of a system are

  • A. cc
  • B. ∘C
  • C. J
  • D. Pa

Explanation: Enthalpy is a form of energy, so its units are Joules (J).

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Correct answer: J

10360. The change in enthalpy for the reaction: NaOH(aq) +HNO3(aq) →NaNO3(aq) +H2 O(l) is

  • A. Heat of combustion
  • B. Heat of neutralization
  • C. Heat of decomposition
  • D. Heat of formation

Explanation: This reaction involves the neutralization of an acid and a base.

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Correct answer: Heat of neutralization
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