Question

i)Define Avogadro's number and write the numerical value of it.
ii) Find the number of moles in:

(a)176 g of carbon dioxide.
(b) 12.044X1023 number of carbon dioxide molecule.
(c) 12g of nitrogen gas. (N=14,C=12,0=16)​

Answer 1

Answer:

• The mole (or mol) represents a certain number of objects.

• SI def.: the amount of a substance that contains the same

number of entities as there are atoms in 12 g of carbon-12.

• Exactly 12 g of carbon-12 contains 6.022 x 10 23 atoms.

• One mole of H 2O molecules

contains 6.022 x 10 23 molecules.

• 1 mole contains 6.022 x 10 23 entities (Avogadro’s number)

• One mole of NaCl contains 6.022 x 10 23 NaCl formula units.

• Use the mole quantity to count formulas by weighing them.

• Mass of a mole of particles = mass of 1 particle x 6.022 x 1023

• The mass of an atom in amu is numerically the same

as the mass of one mole of atoms of the element in grams.

• One atom of sulfur has a mass of 32.07 amu;

one mole of S atoms has a mass of 32.07 g.

Mass of 1 H atom: 1.008 amu x 1.661 x10-24 g/amu = 1.674 x10-24 g

Mass of 1 mole of H atoms:

1.674 x10-24g/H atom x 6.022 x1023H atoms = 1.008 g

Hope it helps