Presentation on theme: "Concentration Concentration is the amount of solute dissolved in an amount of solution. Molar concentration is called Molarity, or M. M = moles."— Presentation transcript:
1 ConcentrationConcentration is the amount of solute dissolved in an amount of solution.Molar concentration is called Molarity, or M.M = moles of solutevolume of solution in LIf 2.0 moles NaCl is dissolved in 1 L of solution, its concentration is “two molar” and is expressed as 2.0 M NaCl.
2 Steps to make a 1 M solution Example: 1 M NaOH solution Calculate the mass needed.1 mol NaOH g NaOH = g NaOH1 mol NaOHMeasure this amount of NaOH into a beaker, then add about 200 mL solvent to dissolve it.Pour the solution into a 1.0 L volumetric flask.Rinse the beaker with more solvent and add to the flask.Add solvent until the solution meets the line indicating 1.0 L.Stopper the flask and swirl, mix thoroughly.
3 Find MolarityExample 1: What is the molarity of a solution made with 3.66 moles solute in L? M = mol = 3.66 mol = L .500 L7.32 M
4 Find Molarity, given mLEx. 2: What is the molarity of a solution made with1.50 mole solute in 250 mL? In order to find M, need volume in L: 250 mL | 1 L____ = _____L | 1000 mL (or move decimal to left 3 places) M = mol = 1.50 mol = ______ M _____ L.250 L6.0 M
5 Find Molarity, given grams Ex. 3: What is the molarity of a solution made with 55.0 g KCl in L? In order to find M, need moles first: 55g KCl | 1 mol KCl = _____mol KCl | 74.5 g KCl M = mol = . mol = ______ M KCl L .500 L.738 mol1.48 M
6 Find MolesEx. 4: How many moles of KCl are in a 100 mL sample of 0.67 M solution? In order to find moles, rearrange the molarity equation: M = mol →mol = (M)(L) = (0.67mol)(0.100L) = L L.067 mol
7 Find Grams 0.67 mol | 74.5 g KCl = | 1mol KCl Ex. 4: How many grams of KCl are in a100. mL sample of M solution?Find moles, then convert to grams using periodic table masses.In order to find moles, rearrange the molarity equation:M = mol →mol = (M)(L) = (0.67mol)(0.100L) =L L0.67 mol | 74.5 g KCl =| 1mol KCl.067 mol4.99 g
8 Find VolumeTo produce 23.4 g of K2CrO4 from 6.0 M K2CrO4, what volume of the solution is needed?Given: g K2CrO4 neededconcentration of solution = 6 moles K2CrO4 per 1 LWant: volume of K2CrO4 in solution23.4 g K2CrO mol K2CrO =194.2 g K2CrO40.120 mol K2CrO4 1 L = mol K2CrO40.120 mol K2CrO40.020 L K2CrO4 soln