1. 1.1.7 Moles and Solutions Calculate the amount of substance, in mol using solution volume and concentration Describe a solutions concentration using the terms concentrated and dilute You will be able to…

2. dissolving solution saturated solubility solute solvent

3. A solution solvent solute  A solution is a mixture of a solvent and a solute.  The liquid is the solvent.  The solid, liquid or gas dissolved in that liquid is the solute.

4. Concentration dilute concentrated - small amount of solute in the solvent - large amount of solute in the same amount of solvent

5. Concentration saturated - large amount of solute in the same amount of solvent, with some solute unable to dissolve

8. Why solutes dissolve

9. A water molecule, H 2 O Because of the properties of the individual atoms there is an uneven distribution of the electrons within the molecule, they tend to cluster towards the oxygen atom δ - δ + The molecule is POLAR

10. If the solute is a positive ion, eg Na+ The polar water molecules cluster around the solute, thereby allowing it to dissolve

11. Calculating concentrations

12.  The two things that decide the concentration of a solution are: ―The number of particles of solute ―The amount of solvent it is dissolved in.  Numbers of particles are measured in moles.  Amounts of solution are measured by the volume used.

13. Volumes  Concentrations are measured per litre of solvent.  One litre of a solvent is 1000cm 3.  Another unit for a litre is dm 3 (‘decimetre cubed’.) A decimetre is 10cm. 10 cm x 10 cm x 10 cm = 1000cm 3 10 cm

14. Volumes  Concentrations are measured per litre of solvent.  One litre of a solvent is 1000cm 3.  Another unit for a litre is dm 3 (‘decimetre cubed’.) When working out a concentration you must always convert the volume into dm 3. e.g. 200 cm 3 = 200 = 0.2dm 3 1000

15. Concentration Concentration = number of moles ÷ volume cnv c n v x  Concentrations are measured in moles per decimetre cubed (mol/dm 3.)  Moles per decimetre cubed (mol/dm 3.) is sometimes written as M.

16. Questions What is the concentration of: a)58.5g NaCl in 2000cm 3 water? b)5.85g NaCl in 2000cm 3 water? c)5.85g NaCl in 500cm 3 water? d)34g NH 3 in 200cm 3 water? Atomic masses Na = 23 Cl = 35,5 N = 14 H = 1 Answers a)0.5M (1 mole ÷ 2 dm 3 ) b)0.05M (0.1 mole ÷ 2 dm 3 ) c)0.2M (0.1 mole ÷ 0.5 dm 3 ) d)10M (2 mole ÷ 0.2 dm 3 )

17. How much have I used? Imagine this represents one dm 3 of a 2M solution (2 moles in 1000cm 3 of water.).

18. In a reaction I only need to use 250cm 3 of this. How many moles is that?

19.  I have used 250/1000 cm 3 of the solution.  This is ¼ of the total.  I would expect to get ¼ of the number of particles of solute in that.  There were 2 moles in the original 1000cm 3.  ¼ of 2 moles = 0.5 moles.

20. How much have I used? Moles used = volume used in cm 3 x concentration 1000 Questions HCl is hydrochloric acid. How many moles of HCl are in: a)200 cm 3 of 1M HCl? b)250 cm 3 of 4M HCl? c)600 cm 3 of 2M HCl? d)400 cm 3 of 0.5M HCl? e)2500cm 3 of 0.1M HCl?