Free Moles and Avogadro's Number MCQs with Answers

• A. 22%
• B. 11.11%
• C. 31.13%
• D. 15.15%

Explanation: In 1 mole of water, H2O, the mass of hydrogen is 2 g and the molar mass of water is 18 g, so hydrogen by mass is (2 g / 18 g) x 100 =…

• A. 14.34%
• B. 18.56%
• C. 13.86%
• D. None of these

Explanation: The molar mass of KNO3 is 39.10 g/mol + 14.01 g/mol + 3 x 16.00 g/mol = 101.11 g/mol.

• A. 57% N
• B. 73% N
• C. 46% N
• D. 53% N

Explanation: Urea is CO(NH2)2, with molar mass 12 + 16 + 2(14) + 4(1) = 60 g mol^-1.

• A. C2H2O4
• B. CH2
• C. CH2O
• D. CHO2

Explanation: Convert each mass to moles: carbon = 24 g ÷ 12 g mol^-1 = 2 mol, hydrogen = 2 g ÷ 1 g mol^-1 = 2 mol, and oxygen = 64 g ÷ 16 g mol^-1 = 4…

• A. 53.4 grams
• B. 54.4 grams
• C. 55.4 grams
• D. 56.4 grams

Explanation: The molar mass of NH3 is 14.0 g/mol + 3 x 1.0 g/mol = 17.0 g/mol, so mass = 3.2 mol x 17.0 g/mol = 54.4 g.

• A. 0.2 moles
• B. 0.3 moles
• C. 0.4 moles
• D. 0.5 moles

Explanation: The molar mass of CaCl2 is 40.0 g/mol + 2 x 35.5 g/mol = 111.0 g/mol, so moles = 22.2 g / 111.0 g/mol = 0.20 mol.

• A. 64.5%
• B. 65.6%
• C. 63.5%
• D. 61.5%

Explanation: The molar mass of AgNO3 is 107.9 g/mol + 14.0 g/mol + 3(16.0 g/mol) = 169.9 g/mol.

• A. 74% Fe
• B. 75% Fe
• C. 77% Fe
• D. 78% Fe

Explanation: Percentage of iron = (mass of iron ÷ mass of ore) x 100 = (27.9 g ÷ 35.8 g) x 100 = 77.93%, which rounds to 78% Fe.

• A. 63.012 g/mol
• B. 65.012 g/mol
• C. 70.012 g/mol
• D. 81.011 g/mol

Explanation: Using standard atomic masses, the molar mass of HNO3 is 1.008 g/mol + 14.007 g/mol + 3 x 15.999 g/mol = 63.012 g/mol.

• A. 0.1 M
• B. 1 m
• C. 1 M
• D. 0.1 N

Explanation: The molar mass of NaCl is 58.5 g mol−1, so 58.5 g represents 1 mol. Since this amount is present in 1 dm3 of solution, molarity = 1 mol /…

• A. 180g/dm3
• B. 170g/dm3
• C. 190g/dm3
• D. 195g/dm3

Explanation: A 1 molar solution contains 1 mol of solute in 1 dm3 of solution. Glucose has molar mass 180 g mol−1, so mass = 1 mol dm−3 × 180 g mol−1 =…

• A. normality
• B. molarity
• C. molality
• D. mole fraction

Explanation: Molality is defined as the number of moles of solute present in 1 kg of solvent, with units mol kg−1.

• A. Value of a
• B. Mass
• C. Atoms
• D. Both B and C

Explanation: Each sample contains 0.5 mol of molecules, so both have 0.5 x 6.022 x 10^23 = 3.011 x 10^23 molecules.

• A. Quantitative analysis
• B. Qualitative analysis
• C. Stochiometery
• D. Physical chemistry

Explanation: Quantitative analysis determines the amount or concentration of each component in a sample, using measurements and calculations.

• A. Stoichio chemistry
• B. Physical chemistry
• C. Analytical chemistry
• D. Quantum chemistry

Explanation: Analytical chemistry includes both qualitative analysis, which identifies components, and quantitative analysis, which measures their…

• A. 6.022 x 10^23
• B. 3.01 x 10^23
• C. 2 x NA
• D. 4 x 6.022 x 10^23

Explanation: The molar mass of NaCl is 23.0 g/mol + 35.5 g/mol = 58.5 g/mol. Thus 29.25 g ÷ 58.5 g/mol = 0.5 mol, and 0.5 mol x 6.022 x 10^23 formula…

• A. macromolecule
• B. macromolecule
• C. molecularity
• D. atomicity

Explanation: Atomicity is the number of atoms present in one molecule of an element or compound, such as two atoms in O2 or three atoms in O3.

• A. 22.4 dm3
• B. 2.24 dm3
• C. 1.12 cm3
• D. 1.12 dm3

Explanation: The molar mass of CO is 12 g mol-1 + 16 g mol-1 = 28 g mol-1. Thus 1.4 g ÷ 28 g mol-1 = 0.050 mol, and at STP its volume is 0.050 mol x…

• A. moles dm-3
• B. moles kg-1
• C. gram dm-3
• D. none

Explanation: Molality is defined as the number of moles of solute dissolved in 1 kilogram of solvent, so its unit is moles kg-1.

• A. identification of elements
• B. estimation of amounts of elements
• C. molar ration of elements
• D. molar volume of elements

Explanation: Qualitative analysis answers the question of what is present, so it is used to identify the elements or ions in a sample.