Moles = Mass => 4.0 = 0.1 / 1.0 x 10 -1 moles mass 40 (ii) 250 cm3 solution in the volumetric flask. Moles in 250 cm3 = 0.1 / 1.0 x 10 -1 moles (iii) one decimeter of solution Method 1 in decimeters = = Moles x 1000cm3/1dm3 Molarity Volume of solution => 1.0 x 10 -1 x 1000cm3 = 250cm3 = 0.4 M / 0.4 molesdm-3 Method 2 250cm3 solution contain 1.0 x 10 -1 moles 1000cm3 solution = Molarity contain 1000 x 1.0 x 10 -1 moles 250 cm3 = 0.4 M / 0.4 molesdm-3 Theoretical sample practice 1. Calculate the molarity of a solution containing: (i) 4.0 g sodium hydroxide dissolved in 500cm3 solution mass of NaOH = (23 + 16 + 1) = 40g Moles = Mass => 4.0 = 0.1 / 1.0 x 10 -1 moles Molar mass 40 Method 1 Moles in decimeters = Molarity = Moles x 1000cm3/1dm3 Volume of solution => 1.0 x 10 -1 moles x 1000cm3 500cm3 = 0.2 M / 0.2 molesdm-3
Moles = Mass => 4.0 = 0.1 / 1.0 x 10 -1 moles mass 40 (ii) 250 cm3 solution in the volumetric flask. Moles in 250 cm3 = 0.1 / 1.0 x 10 -1 moles (iii) one decimeter of solution Method 1 in decimeters = Molarity = Moles x 1000cm3/1dm3 Volume of solution => 1.0 x 10 -1 x 1000cm3 = 250cm3 = 0.4 M / 0.4 molesdm-3 Method 2 250cm3 solution contain 1.0 x 10 -1 moles 1000cm3 solution = Molarity contain 1000 x 1.0 x 10 -1 moles 250 cm3 = 0.4 M / 0.4 molesdm-3 Theoretical sample practice 1. Calculate the molarity of a solution containing: (i) 4.0 g sodium hydroxide dissolved in 500cm3 solution mass of NaOH = (23 + 16 + 1) = 40g Moles = Mass => 4.0 = 0.1 / 1.0 x 10 -1 moles Molar mass 40 Method 1 Moles in decimeters = Molarity = Moles x 1000cm3/1dm3 Volume of solution => 1.0 x 10 -1 moles x 1000cm3 500cm3 = 0.2 M / 0.2 molesdm-3
the-mole.docx