Question

One mole of beryllium (be) contains the same number of atoms as 22.99 g of sodium. There are about 2.007×1023 atoms in 9.0 g al. One mole of calcium (ca) weighs about as much as two moles of neon (ne). 11.495 g of sodium contains 6.022×1023 atoms.

Answer 1

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