calculate the number of atoms in the following
1)13.8g of sodium
2)0.02 moles of aluminium
3)14.2g of sodium sulphate
1) To calculate the number of atoms in 13.8g of sodium we need to use the formula:
Number of atoms = (mass in grams/molar mass) x Avogadro's number
The molar mass of sodium is 22.99 g/mol. Therefore, the number of atoms in 13.8g of sodium is:
(13.8/22.99) x 6.02 x 10^23 = 3.6 x 10^23 atoms
2) To calculate the number of atoms in 0.02 moles of aluminium we use Avogadro's number (6.02 x 10^23) since one mole of any substance contains 6.02 x 10^23 particles (atoms, molecules or ions).
Therefore, the number of atoms in 0.02 mol of aluminium is:
0.02 x 6.02 x 10^23 = 1.20 x 10^22 atoms
3) We need to find the number of atoms in 14.2g of sodium sulphate (Na2SO4). First, we need to calculate the molar mass of sodium sulphate:
Na: 2 x 22.99 = 45.98 g/mol
S: 32.07 g/mol
O: 4 x 16.00 = 64.00 g/mol
Total molar mass = 45.98 + 32.07 + 64.00 = 142.05 g/mol
Now, we can use the same formula as before:
Number of atoms = (mass in grams/molar mass) x Avogadro's number
(14.2/142.05) x 6.02 x 10^23 = 6.02 x 10^22 atoms of sodium sulphate
Since each molecule of sodium sulphate contains 2 sodium atoms, we need to multiply the above result by 2 to get the total number of sodium atoms:
6.02 x 10^22 x 2 = 1.20 x 10^23 sodium atoms.