Question

Calculate the no. of particles in -
(a) 13 moles of helium
(b) 23 g of sodium
(c) 49 g of sulphuric acid


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Answer 1

To calculate the number of particles in a given amount of a substance, we need to know the molar mass of the substance and the number of moles of the substance.

(a) The molar mass of helium is 4 g/mol, so 13 moles of helium is equal to 13 mol * 4 g/mol = 52 g of helium. Since the Avogadro constant is 6.022 x 10^23 particles/mol, there are 6.022 x 10^23 * 13 mol = 7.829 x 10^24 particles of helium in 13 moles of helium.

(b) The molar mass of sodium is 23 g/mol, so 23 g of sodium is equal to 23 g / 23 g/mol = 1 mol of sodium. Therefore, there are 6.022 x 10^23 particles/mol * 1 mol = 6.022 x 10^23 particles of sodium in 23 g of sodium.

(c) The molar mass of sulfuric acid is 98 g/mol, so 49 g of sulfuric acid is equal to 49 g / 98 g/mol = 0.5 mol of sulfuric acid. Therefore, there are 6.022 x 10^23 particles/mol * 0.5 mol = 3.011 x 10^23 particles of sulfuric acid in 49 g of sulfur.