Question

only one isotope is this element occurs in nature. it is found 1.1879x10^23 atoms of this isotope weights 5.322g. identify the element and give its atomic weight.

Answer 1

According to Avogadro’s number, one mole of a substance contains 6.023 x 10²³ numbers of atoms or molecules.

Thus, number of moles of given element can be calculated as follows:

Moles of elements = Total number of atoms / Avogadro’s number

Moles of elements = (1.1879x10²³) / (6.023 x 10²³)

Moles of elements = 0.19723

Since, weight of 1.1879x10²³ atoms (i.e. 0.19723 moles) of given element is 5.322g. Weight of 1 mole of element can be calculated as follows:

Weight of 1 mole of given element = 5.322 g / 0.19723 mol

Weight of 1 mole of given element = 26.98 g/mol

Thus, atomic weight of given element is 26.98

From periodic table of elements it can be concluded that aluminium has molar mass 26.98 g/mol.

Therefore, given element is Aluminium.