1. 1.5 Solutions

2. Starter Moles How many moles are in 45g of NH 4 Cl

3. Objectives To KNOW the terms SOLVENT, SOLUTE, SOLUTION, CONCENTRATION To BE ABLE TO calculate the concentration of solutions. To UNDERSTAND when solutions are more or less concentrated and explain why.

4. A solution is a homogeneous mixture of 2 or more substances. It is made of a solvent and a solute.

5. SOLUTE – the part of a solution that is being dissolved (usually the lesser amount) SOLVENT – the part of a solution that dissolves the solute (usually the greater amount) Solute + Solvent = Solution SoluteSolventExample solidsolid Metal alloys solidliquid Kool aid liquidliquid Alcoholic drinks gasliquidPepsi gasgasair

6. What is Concentration? It is a measure of how many SOLUTE particles there are in a SOLVENT. There more particles there are the more concentrated the SOLUTION is.

7. Concentration of Solute The amount of solute in a solution is given by its concentration. Molarity (M) = moles solute (moles) volume of solution (dm 3 )

8. Concentration If something is concentrated it has more moles/grams of solute per amount of solvent. Ex: 12 M HCl If something is dilute it has less moles/grams of solute per amount of solvent Ex: 0.10 M HCl

9. Questions Calculate the concentration of the solution formed when 4.00 moles of glucose are dissolved in 5.00 dm -3 If 2.00g of sodium hydroxide is dissolved in 200 cm 3 of water, determine the concentration of the resulting solution. What mass of hydrated copper (II) sulphate crystals is present in 17.3 cm 3 of a 0.279 mol dm -3 solution of copper(II)sulphate.

10. PROBLEM: Dissolve 10.00 g of NaCl in water to make 500cm 3 of solution. Calculate the Molarity. Step 1: Calculate moles of NaCl Step 2: Calculate Molarity [NaCl] = 0.34 M m=n x M 10 = n x 58.5 n = 0.17 moles C = n/V C =0.17/0.5 C=0.34 molesdm -3

11. PROBLEM: Dissolve 5.00 g of NiCl 2 6 H 2 O in enough water to make 250 mL of solution. Calculate the Molarity. Step 1: Calculate moles of NiCl 2 6H 2 O Step 2: Calculate Molarity NiCl 2 6 H 2 O [NiCl 2 6 H 2 O ] = 0.0841 M

12. Practice Questions Calculate the concentration of the following: 6g LiOH in 250cm 3 of water 4g Mg(NO 3 ) 2 in 2dm 3 of water 3.8g of C2H5OH in 500cm 3 of acetone. 5.5g Calcium sulphate in 200cm 3 of water. 1kg Magnesium carbonate in 10dm 3 of water.

13. Step 1: Change cm 3 to dm 3. 250 mL * 1 dm 3 /1000cm 3 = 0.250 dm 3 Step 2: Calculate. Moles = (0.0500 mol/ dm 3 ) (0.250 dm 3 ) = 0.0125 moles Step 3: Convert moles to grams. (0.0125 mol)(90.00 g mol -1 ) = 1.13 g moles = MV What mass of oxalic acid, H 2 C 2 O 4, is required to make 250 mL of a 0.0500 M solution?

14. IB Note Square brackets [0.60] means 0.60 M or 0.60 mol/L or 0.60 mol dm -3 This is what IB uses! Note: Can Also use g dm -3 (g/dm 3 ) Is the number of grams of solute dissolved per dm 3 of solution

15. Questions Calculate the volume to which 20cm -3 of 7.63 mol dm -3 hydrochloric acid must be diluted to produce a solution with a concentration of exactly 5.00 mol dm -3

16. Calculate the amount of hydrochloric acid (in mol) present in 23.65 cm 3 of 0.100 mol dm -3 HCl(aq)?

17. Molarity = mol dm -3 so Molarity x dm 3 = mol mol = 0.100 mol dm -3 x.02365 dm -3 =.002365 mol HCl grams =.002365 mol x 36.46 g mol -1 =.0862 g HCl

18. What volume of a 1.25 mol dm -3 potassium permanganate solution, KMnO 4 (aq), contains 28.6 grams KMnO 4 ?

19. Molarity = mol dm -3 so dm -3 = mol/Molarity mol = 28.6 g / 158.04 g mol -1 =.181 mol dm -3 =.181 mol/1.25 mol dm -3 =.145 dm 3

20. What will be the concentration of the solution formed by mixing 200 cm 3 of 3.00 mol dm -3 HCl(aq) with 300 cm 3 of 1.50 mol dm -3 HCl(aq)?

21. Find total moles.200 dm -3 x 3.00 mol dm -3 =.600 mol HCl.300 dm -3 x 1.50 mol dm -3 =.450 mol HCl Total moles = 1.050 mol Find total volume:.200 dm 3 +.300 dm 3 =.500 dm 3 Concentration: 1.050 mol/.500 dm 3 = 2.10 mol dm -3

22. Terms to Know Molar mass Mole Avogadro’s constant Chemical equation Molar ratio Solute Solvent Solution Concentration