Presentation on theme: "How to mix a Standard Solution"— Presentation transcript:
1 How to mix a Standard Solution Use a VOLUMETRIC FLASK to make a standard solution of known concentrationStep 1> add the weighed amount of solute in the volumetric flaskStep 2> add distilled water (about half of final volume)Step 3> cap volumetric flask, and shake to dissolve solute completelyStep 4> add distilled water to volume marker (calibration mark)The solution process may be exothermic (release heat). This may cause the liquid to show a larger volume than is real. Allow the solution to return to ambient (room) temperature and check volume again.Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 480
2 Process of Making a Standard Solution from Liquids Solutions can be made using liquids or solids (or gases).To make a 5% solution v/v (volume to volume)This means to add 5 mL of solute in 95 mL of solvent. The total is 5 mL / 100 mL or 5%.For the diagram add 25 mL of liquid solute and add water to bring volume to 500 mL (about 475 mL water).Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 483
3 Markings on Glassware Beaker 500 mL + 5% Range = 500 mL + 25 mL Graduated CylinderVolumetric Flask500 mL mLRange = – mLTC 20oC “to contain at a temperature of 20 oC”22TD “to deliver”Ts“time in seconds”
4 Concentration…a measure of solute-to-solvent ratio concentrated dilute“lots of solute” “not much solute”“watery”Add water to dilute a solution; boil water off to concentrate it.
5 A. mass % = mass of solutemass of sol’nB. parts per million (ppm) also, ppb and ppt-- commonly used for minerals orcontaminants in water suppliesC. molarity (M) = moles of soluteL of sol’n-- used most often in this classmolLMD. molality (m) = moles of solutekg of solvent
6 WRONG7.85 kg KCl are dissolved in 2.38 L of solution.Find molality.24.8 g table sugar (i.e., sucrose, C12H22O11) are mixed into 450 g water.Find molality.
7 What mass of CaF2 must be added to 1,000 L of water so that fluoride atoms are present at a conc. of 1.5 ppm?= 3.34 x 1028 m’cules H2O
8 molLMHow many moles solute are required to make 1.35 L of 2.50 M solution?mol = M L = 2.50 M (1.35 L) =3.38 molA. What mass sodium hydroxide is this?B. What mass magnesium phosphate is this?
9 Find molarity if 58.6 g barium hydroxide are in 5.65 L solution.
10 You have 10.8 g potassium nitrate. How many mL of solution will make this a 0.14 M solution?convert to mL
11 Concentration The amount of solute in a solution. Describing Concentration% by mass - medicated creams% by volume - rubbing alcoholppm, ppb - water contaminantsmolarity - used by chemistsmolality - used by chemists
12 SAWS Water Quality Report - June 2000 ConcentrationSAWS Water Quality Report - June 2000
13 Molalitymass of solvent only1 kg water = 1 L water
14 MolalityFind the molality of a solution containing 75 g of MgCl2 in 250 mL of water.75 g MgCl21 mol MgCl295.21 g MgCl20.25 kg water= 3.2m MgCl2
15 MolalityHow many grams of NaCl are req’d to make a 1.54m solution using kg of water?0.500 kg water1.54 mol NaCl1 kg water58.44 g NaCl1 mol NaCl= 45.0 g NaCl
16 Molarity of Solutions Molarity of Solutions Molarity of Solutions