Mole Concept — Set 1
Chemistry · मोल संकल्पना · Questions 1–10 of 40
One mole is defined as the amount of substance that contains?
Correct Answer: D. 6.022 × 10^23 elementary entities
Option D is correct because one mole contains Avogadro’s number of entities. These entities can be atoms, molecules, ions, or electrons. Avogadro’s constant is about 6.022 × 10^23 per mole.
The value of Avogadro’s constant is approximately?
Correct Answer: B. 6.022 × 10^23 mol^-1
Option B is correct because Avogadro’s constant is about 6.022 × 10^23 mol^-1. It tells how many particles are in 1 mole. It links microscopic particles with macroscopic amount.
At STP, the molar volume of an ideal gas is closest to?
Correct Answer: D. 22.4 L
Option D is correct because 1 mole of an ideal gas occupies about 22.4 L at STP. This value is used to convert between moles and gas volume at STP. Half a mole at STP occupies about 11.2 L.
The molar mass of carbon dioxide (CO2) is?
Correct Answer: D. 44 g/mol
Option D is correct because CO2 has molar mass 12 + 16 + 16 = 44 g/mol. Molar mass is the mass of 1 mole of a substance. It is numerically equal to molecular mass in grams.
How many moles of water (H2O) are present in 9 g of water? (H=1, O=16)?
Correct Answer: B. 0.50 mol
Option B is correct because moles = mass/molar mass = 9/18 = 0.50 mol. The molar mass of water is 18 g/mol. Moles help convert mass into number of molecules.
How many molecules are present in 0.25 mol of oxygen gas (O2)?
Correct Answer: A. 1.5055 × 10^23
Option A is correct because molecules = moles × NA = 0.25 × 6.022 × 10^23. This gives 1.5055 × 10^23 molecules. NA is the number of particles in 1 mole.
The empirical formula of a compound represents?
Correct Answer: D. The simplest whole-number ratio of atoms
Option D is correct because empirical formula gives the simplest whole-number ratio of atoms. It may not show the actual molecular composition. The molecular formula is a whole-number multiple of the empirical formula.
Which statement is correct about molecular formula and empirical formula?
Correct Answer: A. Molecular formula is a whole-number multiple of empirical formula
Option A is correct because molecular formula = n × empirical formula. The value of n is a positive integer. If n = 1, both formulas become the same.
Avogadro’s law states that at constant temperature and pressure?
Correct Answer: B. Equal volumes of gases contain equal numbers of molecules
Option B is correct because equal volumes of gases at the same T and P have equal numbers of molecules. This means volume is proportional to number of moles for gases. The law is useful for gas calculations and comparisons.
The molarity (M) of a solution is defined as?
Correct Answer: A. Moles of solute per liter of solution
Option A is correct because molarity is moles of solute divided by liters of solution. It depends on the final volume of the solution. Molarity is commonly used in laboratory solutions.