1) the number of atoms (or molecules or ions) in one mole of any substance is same= 6.023 X 10^23
Thus as mass of one mole of sodium = 22.99 grams, this is equal to molar mass of sodium
moles of sodium = mass / molar mass = 22.99/22.99 = 1
Thus number of atoms in Be will be same the number of atoms of 22.99g of sodium
2) The mass of aluminium is given = 9g
atomic mass of Al = 27
Moles of Al = mass / molar mass = 9/ 27 = 1/3
The atoms of Al in one mole = 6.023 X 10^23
Hence atoms of Al in 1/3 moles of Al = 6.023 X 10^23 / 3 = 2.007 X 10^23
So given statement is true
3) The mass of one mole of Ca = 40grams
The mass of one mole of Neon = 20grams
So yes one mole of Ca will weigh equal to two moles of Ne
4) The atomic mass of sodium = 23 g / mole
Thus 23 grams of sodium contains 6.022×1023 atoms and not 11.495 g of sodium
