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Free Fundamental Concepts of Chemistry MCQs with Answers

894 Fundamental Concepts of Chemistry MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Mole calculations connect mass, number of particles and Avogadro's number, while balanced equations provide the mole ratios used in stoichiometry. Questions cover limiting and excess reactants, theoretical yield and percentage yield, including identifying which reactant is consumed first and comparing the actual product with the maximum possible product.

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Moles and Avogadro's NumberLimiting and Excess ReactantsTheoretical and Percentage Yield
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894 questions · page 33 of 45

641. How many times sodium is heavier than atom of hydrogen?

  • A. 21 times
  • B. 22 times
  • C. 23 times
  • D. 24 times

Explanation: Explanation for this question will be added soon!

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Correct answer: 23 times

642. This set of Organic Chemistry Multiple Choice Questions & Answers (MCQs) focuses on "Classification of Organic Compounds".

  • A. Open chain compounds and acyclic compounds
  • B. Open chain compounds and linear chain compounds
  • C. Cyclic compounds and alicyclic compounds
  • D. Alicyclic compounds and acyclic compounds

Explanation: The explanation for this question will be added soon!

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Correct answer: Alicyclic compounds and acyclic compounds

643. The formula with shows the simplest whole number ratio for the atoms of different elements in compound

  • A. Ionic formula
  • B. Structural formula
  • C. Empirical formula
  • D. Molecular formula

Explanation: It shows the simplest ratio for the atoms of different elements in a compound.

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Correct answer: Empirical formula

644. Number of moles present in 0.6 gram of silica is (atomic mass si=28 ,O=16)

  • A. 0.01 mole
  • B. 0.064 mole
  • C. 0.044 mole
  • D. 0.054 mole

Explanation: Silica means Silicon dioxide(SiO2), Molecular mass= 60 ● Mole= Mass / Mr = 0.6 / 60 = 0.01 mol

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Correct answer: 0.01 mole

645. The number of moles of co2 which contain 8 gram of oxygen is

  • A. 0.25
  • B. 0.75
  • C. 0.50
  • D. 1.0

Explanation: CO2 : O 1mole : 32g X : 8 X= 0.25 moles.

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Correct answer: 0.25

646. Number of moles of NO2 which contains 24 gram oxygen is

  • A. 1.0
  • B. 0.25
  • C. 0.50
  • D. 0.75

Explanation: NO2 : O 1 mole : 32 g X : 24g X= 0.75 mol.

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Correct answer: 0.75

647. It STP 0.5 mole of a case occupy a volume of

  • A. 22.4dm³
  • B. 11.2dm³
  • C. 44.8dm³
  • D. None

Explanation: Volume = Moles x 22.4dm3 = 0.5 x 22.4 = 11.2dm³.

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Correct answer: 11.2dm³

648. In reaction A+2B---C4 moles of A and 10 moles of B will produce:

  • A. 4 moles of C
  • B. Five moles of C
  • C. 8 moles of C
  • D. None of these

Explanation: According to equation A is acting as the limiting reagent so do calculations using A 1A = 1C Hence 4A = 4C

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Correct answer: 4 moles of C

649. 200dm3 of CO is burnt completely according to the reaction 2CO+O2---2CO2 What volume of O2 will be required?

  • A. 100dm3
  • B. 50dm3
  • C. 60dm3
  • D. 70dm3

Explanation: 2x24dm3 of CO => 24dm3 of O2 200dm3 => xdm3 x=100dm3

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Correct answer: 100dm3

650. efficiency of a chemical reaction can be checked by calculating

  • A. Amount of limiting reactant
  • B. Amount of reactant in excess
  • C. Amount of product formed
  • D. Amount of reactant left unused

Explanation: The efficiency of a chemical reaction can assessed by calculating the amount of product formed because it provides a measure of how…

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Correct answer: Amount of product formed

651. two mole of H2S and 11.2 dm³ of SO2 at STP react according to the following equation SO2+2H2S---2H2O+3S What will be the number of moles of sulphur formed in the reaction?

  • A. 1.5
  • B. 11.2
  • C. 3
  • D. 6

Explanation: 1mol => 22.4dm3 at STP xmol => 11.2dm3 at STP x= 0.5mol SO2+2H2S---2H2O+3S 1mol. 2mol. 3mol 0.5mol 2mol.

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Correct answer: 1.5

652. methanol burns according to the following equation 2CH3OH+3O2---2CO2+4H2O If 4.50 moles of methanol are burnt in oxygen than how many moles of water are produced

  • A. 4.5 moles
  • B. 2.25 moles
  • C. 9 moles
  • D. 6 moles

Explanation: 2CH3OH => 4H2O 4.5CH3OH => xH2O x= 9moles

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Correct answer: 9 moles

653. researcher has prepared a sample of 1-bromopropane from 10 gram of 1-propanol after purification he made 12 gram of product which of the following is percent yield

  • A. 58%
  • B. 70%
  • C. 50%
  • D. 90%

Explanation: Mr of 1-propanol= 60g/mol Mr of 1-bromopropane= 122.9g/mol 60g => 122.9g 10g => xg x= 20.5 Percentage Yield = (Actual Yield / Theoretical…

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Correct answer: 58%

654. actual yield is less than theoretical yield because

  • A. Reversibility of reaction
  • B. In experienced worker
  • C. Competing side reaction
  • D. All

Explanation: This answer is correct as all the above options effects the yield of a chemical reaction hence this is the best possible option.

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Correct answer: All

655. considering the equation, S+O2=SO2 32g of sulphur reacts with 32g of oxygen to give 64g of SO2 the 64g of SO2 produced is called

  • A. Actual yield
  • B. Ideal yield
  • C. Practical yield
  • D. Experimental yield

Explanation: This answer is the best as the 64g of SO2 produced is actual yield and the theoretical yield is also 64g hence this is considered as ideal…

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Correct answer: Ideal yield

656. Equal moles of all gasses at STP have

  • A. Same mass but different volumes
  • B. Different masses but the same volume
  • C. Same mass and same volume
  • D. Different volume and different masses

Explanation: ● Volume = mole x 22.4dm³ Moles equal means volume equal ● Mole= Mass/ Mr Mass = Mole x Mr All gases would have different Molecular mases…

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Correct answer: Different masses but the same volume

657. The Avogadro's number of atom or molecule or formula unit of a substance is called its

  • A. Mole
  • B. Molecular weight
  • C. Molecular mass
  • D. None of these

Explanation: The Avagadro's number is a constant representing the number of atoms or molecules in one mole of a substance and the term "mole" is the…

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Correct answer: Mole

658. The number of moles of Cr2O7 needed to oxidize 0.136 equivalent of N2H5 according to the reaction is: N2H5+ + Cr2O7 2- --> N2Cr3+ + H2O is:

  • A. 0.136
  • B. 0.272
  • C. 0.816
  • D. 0.0227

Explanation: Following is the solution to this question:

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Correct answer: 0.0227

659. A carbon compound containing carbon and oxygen has an approximate molar mass equal to 290. On analysis, it is found to contain 50% by mass of each element. Therefore molecular formula of the compound is:

  • A. C12O9
  • B. C4O3
  • C. C3O4
  • D. C9O12

Explanation: Let the mass of the compound = 100g mass of oxygen = 50g moles of oxygen= 50/16 mass of carbon = 50 g moles of carbon= 50/12 mole ratio of…

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Correct answer: C12O9

660. The pair of species having the same percentage of carbon is:

  • A. CH3COOH and C6H12O6
  • B. CH3COOH and C2H5OH
  • C. HCOOCH3 and C12H22O11
  • D. C6H12O6 and C12H22O11

Explanation: Mass number of CH3COOH = (2x12) + (4x1) + (2x16) = 60Percentage of carbon = 24/60 x 100 = 40%Mass number of C6H12O6 = (6x12) + (12x1) +…

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Correct answer: CH3COOH and C6H12O6
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