Answer:
A) 0.30 moles.
B) it contains 0.3 moles of both Na and Cl.
C) it contains 6.023 x 10²³ atoms of both Na and Cl.
Explanation:
A) The number of moles of 17.45 g of NaCl:
n = mass / molar mass,
mass = 17.45 g and molar mass = 58.44 g/mol
The number of moles of NaCl = (17.45 g) / (58.44 g/mol) = 0.298 mol ≅ 0.30 moles.
B) The number of moles of each element in NaCl
NaCl → Na + Cl
Each mole of NaCl contains one mole of Na and one mole of Cl.
using cross multiplication:
1.0 mol NaCl → 1.0 mol Na
0.3 mol NaCl → ??? mol Na
The number of moles of Na atoms in NaCl = (1.0 mol Na x 0.3 mol NaCl) / (1.0 mol NaCl) = 0.3 mol of Na atoms.
by the same way; the number of moles of Cl atoms = (1.0 mol Cl x 0.3 mol NaCl) / (1.0 mol NaCl) = 0.3 mol of Cl atoms.
C) The number of atoms of each element in the sample:
It is known that every mole of a substance contains Avogadro,s number (NA = 6.023 x 10²³) of molecules.
1.0 mole of NaCl → 6.023 x 10²³ molecules
0.3 mole of NaCl → ???? molecules
using cross multiplication:
The number of molecules in 0.3 mole of NaCl = (6.023 x 10²³ x 0.3 mole) / (1.0 mole) = 1.8069 x 10²³ molecules.
Every molecule of NaCl contains one atom of Na and one atom of Cl.
So, it contains 6.023 x 10²³ atoms of both Na and Cl.
