Question

Sodium is represented as 11 Na 23
(i) Write its gram atomic mass.
(ii)Write the formula of the compound formed when sodium reacts with phosphate radical.
(iii) How many atoms of Na will be there in 11.5 g of the sample?
(Given :Atomic mass of Na=23u)

Answer 1

Answer:

Sodium has a mass number of 23amu. Since sodium has 11 protons, the number of neutrons must be 23 – 11 = 12 neutrons.

Answer 2

(i) The gram atomic mass is 23g

(ii)Sodium Phosphate (Na₃PO₄)is an ionic compound formed by two ions, Sodium  and Phosphate

(iii) if 23 g of sodium contains $6.023X10^{23}$ atoms, then 11.5 g  of sodium conatin$3.0115 X10^{23}$  atoms.

Explanation:

Molar mass of Na=23g/mol

no. of moles = weight/molar mass

n = $\frac{11.5}{23}$

no. of moles = 0.5

no. of moles = no. of atoms/avogadro’s number

0.5 = no. of atoms/$6.02210^{23}$

$0.5X6.02210^{23}$ atoms = no. of atoms

$3.0115 X10^{23}$ atoms.