Mole Concept and Molar Masses MCQ Quiz - Objective Question with Answer for Mole Concept and Molar Masses - Download Free PDF

The correct answer is 4 - (c), (b), (a), (d).

Key Points

• Specific heat is the amount of heat required to raise the temperature of a substance's unit mass by one degree Celsius.
• The specific heat values of the given elements are approximately:
  • Silver: 0.24 J/g°C
  • Tungsten: 0.13 J/g°C
  • Carbon: 0.71 J/g°C
  • Aluminium: 0.90 J/g°C
• Arranging in ascending order based on specific heat: Tungsten (c)
• Option 4 correctly reflects the order: (c), (b), (a), (d).
• This sequence is derived from the specific heat values of the elements as per standard reference data.

Additional Information

• Specific heat capacity: A material property that indicates how much heat energy is needed to raise the temperature of a unit mass of a substance.
• Factors affecting specific heat:
  • Bond strength between atoms
  • Atomic mass of the substance
  • Material structure (e.g., crystalline or amorphous)
• Applications: High specific heat materials are used in heat storage systems, while low specific heat materials are ideal for rapid heating applications.
• Comparison: Metals like Silver and Tungsten generally have lower specific heat due to their dense atomic structure, whereas non-metals like Carbon have higher specific heat.
• Specific heat is measured in units such as J/g°C or J/kg°C in the SI system.

Concept:

Normality:

• It is defined as the number of grams equivalent per litre of solution.
• Also known as equivalent concentration.
• Normality = Number of gram equivalents / [volume of solution in litres]

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The Normality of a mixture of solutions is given by N₁v₁ + N₂V₂ + N₃V₃ + ..... = N_rV_r, where N₁, N₂, N₃ are the normality of the components and V₁, V₂, V₃ are their respective volumes.

N_r is the final normality and V_r is the volume of the resultant mixture or the solution.

Calculation:

Given:

Strength N₁ of H₂SO₄ = 10N

Volume V₁ of H2SO4 = 50 mL

Strength N1 of HCl = 12 N

Volume V₂ of HCl = 25 mL

Strength N₃ of HNO3 = 5N

Volume V₃ of HNO3 = 40 mL

Volume of the mixture = V_r = 1000 mL

Normality of the mixture = N_r =?

We know, The Normality of a mixture of solutions is given by N1V1 + N2V2 + N3V3 + ..... = NrVr

Hence,

10 × 50 + 12 × 25 + 5 × 40 = 1000 × N_r

or, N_r ×  1000 = (500 + 300 + 200) = 1000

or, N_r = 1000/1000 = 1.

Hence, the Normality of the final mixture is 1N.

Concept:

• Normality:
  • It is defined as the number of grams equivalent per liter of solution.
  • Also known as equivalent concentration.

​

• Normality is inversely proportional to temperature.
• Unit of normality is g. equivalent. lit-1.

Molality:

• It is defined as the number of moles of solute per kilogram of solvent.
• Unit of Molality is the mole. Kg-1.

​

Molarity:

• It is defined as the moles of a solute per liters of a solution.
• It is also known as the molar concentration of a solution.
• The unit of Molarity is the mole. lit-1.
• It is given by:

• Molarity is inversely proportional to volume.
• Molarity is inversely proportional to temperature.

Calculation:

Given:

Amount of NaOH = w  = 40g

Amount of solvent = 1000 gm H2O

• Molar mass(M) of NaOH = 23 + 16 + 1 = 40 
• ​Hence, no of moles of NaOH = 

Hence, 1 mole of solute is present in 1000g of solvent. Hence, the solution is one molal.

Hence, a solution made of by dissolving 40 gm of NaOH in 1000 gm H2O is 1 molal.

The Correct answer is HNO3 - 62.

Key Points

• The molar mass of a compound is calculated by summing up the atomic masses of all the atoms in its molecular formula.
• For HNO3 (Nitric Acid), the atomic masses of its elements are:
  • H (Hydrogen): 1.008
  • N (Nitrogen): 14.007
  • O (Oxygen): 15.999 (per atom, and there are 3 atoms of oxygen).
• Thus, the molar mass of HNO3 = (1.008) + (14.007) + (3 × 15.999) = 63.012 g/mol.
• The given value of 62 g/mol is incorrect as it does not match the accurate calculated molar mass.
• This makes HNO3 - 62 the incorrect pair in the given options.

Additional Information

• CH4 - 16
  • Methane (CH4) is a simple hydrocarbon composed of one carbon atom and four hydrogen atoms.
  • The atomic masses are:
    • C (Carbon): 12.011
    • H (Hydrogen): 1.008 (per atom, and there are 4 atoms of hydrogen).
  • The molar mass of CH4 = (12.011) + (4 × 1.008) = 16.043 g/mol, which approximates to 16.
• NaCl - 58.5
  • Sodium Chloride (NaCl) is a common salt composed of one sodium atom and one chlorine atom.
  • The atomic masses are:
    • Na (Sodium): 22.990
    • Cl (Chlorine): 35.453
  • The molar mass of NaCl = (22.990) + (35.453) = 58.443 g/mol, which approximates to 58.5.
• HCl - 36.5
  • Hydrochloric Acid (HCl) consists of one hydrogen atom and one chlorine atom.
  • The atomic masses are:
    • H (Hydrogen): 1.008
    • Cl (Chlorine): 35.453
  • The molar mass of HCl = (1.008) + (35.453) = 36.461 g/mol, which approximates to 36.5.

The Correct answer is 0.0578.

Key Points

• The problem involves calculating the percentage composition of hydrogen in an organic compound based on the given data.
• To determine the hydrogen percentage, we use the following formula: (Mass of hydrogen / Mass of the organic compound) × 100.
• In the given problem, the mass of water produced is 0.13 g.
• Water (H₂O) contains 2 parts of hydrogen by weight and 16 parts of oxygen by weight. Thus, the ratio of hydrogen in water is 2/18 = 1/9.
• From the mass of water, the mass of hydrogen can be calculated as: (1/9) × 0.13 g = 0.01444 g.
• The mass of the organic compound is given as 0.26 g.
• Now, the percentage of hydrogen is calculated as: (0.01444 g / 0.26 g) × 100 = 5.78% or 0.0578.
• Hence, the correct answer is 0.0578.

Additional Information

• Key Concept: The calculation of hydrogen percentage is based on the principle of elemental analysis, which is widely used in chemistry to determine the composition of compounds.
• Water as a Product: The combustion of organic compounds typically produces water and carbon dioxide, helping chemists analyze the hydrogen and carbon content.
• Hydrogen in Water: The ratio of hydrogen in water (1/9) is critical in such calculations. This ratio originates from the molecular weight of H₂O (18) and the atomic weight of hydrogen (2).

The correct answer is 18 g.

Key Points

Explanation:

• 0.1 mole of C₆H₁₂O₆ = Molecular mass of C6H12O6 in grams
  • 0.1 (Mass of 6C + Mass of 12H + Mass of 6O)
  • 0.1 (12 × 6 + 1 × 12 + 16 × 6)
  • 0.1 (72 + 12 + 96)
  • 18 grams

• The correct answer is option 4, i.e., 1 mole of Carbon will contain the same number of atoms as present in 1 mole of Helium.
• Out of the given options, the correct statement is: 1 mole of Carbon will contain the same number of atoms as present in 1 mole of Helium.
• A mole is the SI unit of measurement for the amount of substance. 
• 1 mole = 6.022 x 10²³
• 1 mole of any particle has 6.022 x 1023 of that particle. For eg: 1 mole of atom = 6.022 x 1023 atoms, 1 mole of molecule = 6.022 x 1023 molecule, etc.
• 6.022 x 1023 is known as the Avagadro number.
• A mole does not depend on the atomic number, it's just a unit.
• Thus, 1 mole of Carbon and 1 mole of Helium will contain the same number of atoms i.e. 6.022 x 1023 atoms.

Step 1: Finding Atomic Mass:

The atomic mass of hydrogen = 1u

The atomic mass of oxygen = 16u

Molecular mass of water (H2O) = 2 × 1 + 1 × 16 = 18 u

Hence, the Molecular mass of 2 molecules of water = 36 u

Step 2: Concept of Avagadro Constant:

One mole of water contains 6.023 × 10²³ water molecules.

Now,

Mass of water molecule for 36 u =  = 5.98 × 10-23 g

Concept:

• The total number of moles of a compound divided by the total number of moles of all constituents gives us mole fraction.
• Mathematically, it can be expressed as:

Calculate Mole Fractions
For each component (A, B, C), the mole fraction \(X\) is calculated as:

Sum of all mole fraction of all = 1/3 +1/3 + 1/3 = 1

• The total mole fraction of a solution always adds up to 1.

Mole fraction unit is very useful in relating some physical properties of solutions, says vapour pressure with the concentration of the solution and quite useful in describing the calculations involving gas mixtures.

Formula -

Mole Fraction = Moles of one component / Total moles of all component 

X_A+X_B+X_C = (N_A/ N_A+N_B+N_C) + (N_B/ NA+NB+N_C) + (N_C/ NA+NB+N_C) = 1

The correct answer is Increase.

Concept:

• Molarity:
  • It is defined as the moles of a solute per litres of a solution.
  • It is also known as the molar concentration of a solution.
• Molality:
  • It is defined as the number of moles of solute per kilogram of solvent.
• Mole fraction:
  • It is the ratio of moles of a component with the total moles of solute and solvent.
• Mass%:
  • It is the percentage of the mass of solute or solvent w.r.t total mass of solution.
• Formulas:

Explanation:

• Molarity depends on the volume of the solution.
• And volume is directly proportional to temperature.
• And when we increase the temperature the volume will increase.
• So the increase in volume leads to a decrease in Molarity as Molarity is inversely proportional to the volume of solution.

​Additional Information

Notes:

• Normality:
  • It is defined as the number of gram equivalent per litre of solution.
  • Also known as equivalent concentration.
  • Normality = Number of gram equivalents / [volume of solution in litres]
• Normality is inversely proportional to temperature.
• ​Volume is directly proportional to temperature.
• Molarity is inversely proportional to volume.
• Molarity is inversely proportional to temperature.
• Molality is not dependent on temperature.

The correct answer is 35.2 g.

Key PointsAtomic mass of sulphur =32

Mass of 1.1 mol of sulphur = 32*1.1= 35.2 g

Explanation:

• Combustion is a chemical reaction in which a substance reacts quickly with oxygen and produces heat.
• The original substance is referred to as the fuel, and the source of oxygen is referred to as the oxidizer.
• The fuel can take the form of a solid, liquid, or gas.

The Combustion equation for glucose is given as follows;

C₆H₁₂O₆ +6O₂ → 6CO₂  + 6H₂O

From the above balanced equation we can see that,

For complete combustion of 1 mole of glucose we need 6 mole of oxygen gas.

Hence, The number of moles of oxygen gas used in the complete combustion of 1 mole of glucose is 6

The correct answer is 13.

Concept:

• Mole: One mole is the amount of a substance that contains as many particles or entities as there are atoms in exactly 12 g (or 0.012 kg) of the 12C isotope.

Calculation:

• The number of moles in 52 g of He is 1
• The molar mass of helium gas is 4g/mol.
• Given the number of moles of substance=52g

The number of moles= 13g.

Hence the moles present in the 52g of He are 13Additional Information

• Helium:
  • It is a noble gas.
  • It is used for filling balloons and other lighter aircraft.
  • Helium (He), when mixed with O₂, is used by deep-sea divers for breathing and for respiratory patients.

Given:

Mass of common salt (solute) = 41 g

Mass of water (solute) = 320 g

Formula Used:

Concentration of solution = (mass of solute / mass of solution) × 100

calculation:

according to the question

mass of solution = mass of solute + mass of solute

⇒ (41 + 320) g

⇒ 361 g

Now,

Concentration of solution = (mass of solute/mass of solution) × 100

(41/361 × 100)%

⇒ 11.357% ~ 11.36%

The required solution is 11.36%

Concept:

Mole Concept -

•  The quantity one mole of a substance signifies 6.022 × 1023 number of particles of that substance which may be atoms, molecules, or ions.
• The quantity is a universal constant like Dozen, Gross, etc., and is known as Avogadro number, denoted by NA. after the scientist Amedeo Avogadro.
• Examples- In one mole of H2, there are 6.022 × 1023 molecules of hydrogen, and the number of atoms is 2 × 6.022 × 1023, as one molecule of hydrogen contains two-atom each.
• The mass of one mole of a substance is called its Molar Mass (M) or Atomic mass expressed in grams.
• The volume occupied by a mole of gas is 22.4 L at NTP, called its Molar Volume.
• The no. of moles (n) is calculated as =

Number of particles / Avogadro’s number.

To summarise, we can say, 

Calculation:

Given: 

Mass of Oxygen molecule O₂ = 8g

• Molar mass of O₂ = 16 + 16 = 32g
• The number of moles of O₂ in 8g of O₂ =

8/32 = .25 moles 

• 1 mole contains =  6.022 × 1023 number of O2 molecules.
• Then .25 mole will contain =  

6.022 × 1023 × .25 = 1.51 × 1023

Hence, the number of particles in 8g of O2 molecules is 1.51 × 1023.