Chemistry - prepare a solution

Question

Chemist Samo wants to prepare a 100 cm³ solution of sodium chloride with a concentration of

c (NaCl) = 0.500 mol / dm³. In the periodic table, he found that the molar mass of Na is 23.0 g / mol and the molar mass of CI is 35.5 g / mol.

a) Calculate how much g of NaCl needs to be weighed to prepare this solution.

Answer 1

Molar mass NaCl = 23.0 g + 35.5 g = 58.5 g / mol

Volume required = 100 cm³ x 1 dm³ /1000 cm³ = 0.1 dm³

moles = 0.500 mol / dm³ NaCl x 0.1 dm³ = 0.0500 moles NaCl required to make 100 cm³ of 0.500 mol / dm³

mass of NaCl = 0.0500 mols x 58.5 g / mol = 2.93 g NaCl needed (to 3 sig. figs.)