Correct Answer - Option 4 : 3
The correct answer is option 4 i.e. 3.
Calculation:
The number of moles present in 81 grams of aluminium is 3 moles.
\({{Number \ of\ moles}={Mass\ of \ substance \over Mass\ of\ one\ mole}}\)
Mass of substance= 81 grams
Mass of one mole(molar mass) aluminum= 27.
The number of moles=\({81 \over 27}= 3\) moles.
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.
