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Solutions

Solutions. PART IV: Molarity. Review: How to you go from grams of a substance to moles (and vice versa)?. Use molar mass! Ex: How many moles are in 0.50g NaCl? 0.50g x 1mol NaCl = 0.00855 mol NaCl 58.45 g. Concentration. The amount of solute per quantity of solvent

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Solutions

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  1. Solutions PART IV: Molarity

  2. Review: How to you go from grams of a substance to moles (and vice versa)? • Use molar mass! • Ex: How many moles are in 0.50g NaCl? 0.50g x 1mol NaCl = 0.00855 mol NaCl 58.45 g

  3. Concentration • The amount of solute per quantity of solvent • Types of concentrations: • Mass/volume percent • Mass/mass % • Volume/volume% • ppm or ppb • Molar concentration (molarity)

  4. Mass/volume % m/v % = mass of solute (g)___ x 100% volume of solution (mL) Ex: A chemist adds 5.70g of CuCl to 55.0 mL of H2O, what is the m/v percent? 5.70 g x 100% = 10.4% 55.0 mL

  5. Example # 2: A clean wants to make a 1.7% (m/v) solution of TSP, what mass is needed to make 2.0L of solution? • First change % to decimal ( 1.7%  0.017) • Don’t forget to change L to mL!! • Then use formula, solve for x 0.017 = x g__ 2000 mL 0.017 x 2000 = xg 34 = xg He would need to add 34g of TSP

  6. m/m and v/v percentages • Same processes as m/v • m/m (all in grams) • v/v (all in mL)

  7. Parts per million (or billion) • Usually mass/mass relationship ppm = mass solute (g) x 106 mass solution (g) or ppb = mass solute (g) x 109 mass solution (g)

  8. Molarity • Molar concentration is the number of moles in 1.0 L of solution • Molarity (mol/L) = moles solute_______ volume (L) of solution • Also expressed as C = _n__ V

  9. Example from Molarity sheet 

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