Template copyright 2005 www.brainybetty.com Solutions A solution is made up of a solute dissolved in another substance called a solvent. Salt: the solute Water: the solvent Ex: Salt Water 11/8/2018 Template copyright 2005 www.brainybetty.com

Concentration Depending on how much solute we put in the solvent, the concentration of the solution will vary. Concentration of a solution the quantity of solute dissolved in a given quantity of solution

Concentration (molecules) 200mL 200mL 100mL

Concentration 200mL 200mL 100mL

Concentration C (g/L) Ratio of solute to solution Ex: Concecntration of 7g of solute in 1 L of solution would be 7g / L (mass of solute in g) (g/L) (volume of solution in L) m (grams) V (Litres) C (g/L)

Concentration What is the concentration of the solution prepared by adding 1g of salt to 500mL of water? Mass (grams) Concentration (g/L) Volume (Litres)

Calculating concentrations… Concentration can be calculated in several ways… In grams/Litre: C= masssolute in g volumesolution in L In milliltres/litre: C = volumesolute in mL 11/8/2018 Template copyright 2005 www.brainybetty.com

Calculating concentrations… Concentration can also be expressed as a percentage: Ex: Concentration of 5% = 5g/100mL % mass/mass = mass solute x 100 mass solution % mass/Volume= mass solute x 100 Volume solution (ml) % Volume/Volume = Volume solute x 100 Volume solution(ml) 11/8/2018 Template copyright 2005 www.brainybetty.com

Template copyright 2005 www.brainybetty.com Example: Calculate the concentration of 350 mL solution with 28 mL of acetic acid dissolved in it. Csolution = volumesolute = 28 mL = 80 mL/L volumesolution 0.35 L 11/8/2018 Template copyright 2005 www.brainybetty.com

Template copyright 2005 www.brainybetty.com Example (cont’d) Find the concentration of the same solution, but in mL/100 mL 1 L = 1000 mL 80 mL = ? mL 1000 mL 100 mL C= 80 mL x 100 ml = 8 mL 1000 mL The concentration of this acetic acid solution is 80 mL/L or 8 mL/100mL 11/8/2018 Template copyright 2005 www.brainybetty.com

Saturated vs. unsaturated A saturated solution is a solution that has the maximum amount of solute possible dissolved in a given volume of solvent (all extra solute falls to the bottom of the beaker) An unsaturated solution is a solution in which we can still dissolve more solute in a given amount of solvent 11/8/2018 Template copyright 2005 www.brainybetty.com

Template copyright 2005 www.brainybetty.com Solubility Solubility is a physical characteristic property that defines the maximum amount of solute that can be dissolved in a given amount of solvent at a specific temperature and pressure 11/8/2018 Template copyright 2005 www.brainybetty.com

Template copyright 2005 www.brainybetty.com Insolubility There are some molecules which are not attracted by certain solvents. For example, you can’t dissolve oil in water because oil particles are more attracted to each other than to water molecules 11/8/2018 Template copyright 2005 www.brainybetty.com

Template copyright 2005 www.brainybetty.com Factors that affect the rate if dissolution: How can we make something dissolve faster?? Crushing the solute: increases surface area of contact with solvent Aggitation (shaking/stirring) makes molecules move faster, leaving more space between molecules and allowing solute and solvent molecules to come into contact more quickly Heating: particles have more energy and collide more (dissolve more) 11/8/2018 Template copyright 2005 www.brainybetty.com

Concentrated or Dilute? Concentrated solutions have a lot of solute dissolved in a given amount of solvent Dilute solutions have a little solute dissolved in a given amount of solvent 11/8/2018 Template copyright 2005 www.brainybetty.com

Dilution Dilution is the procedure of making a final solution that is weaker (less concentrated) than the initial solution by adding more solvent to it. When dilution happens, the solute is more spread out in the solvent. Ex:. Concentrated soups need to be mixed with one can of water.

Two ways to dilute a solution 1: Add solvent to a solution (adding water to frozen juice) 2: Add a concentrated solvent to a solution to obtain desired quantity (chocolate syrup in milk) 11/8/2018 Template copyright 2005 www.brainybetty.com

Formula for dilutions C1 V1 = C2 V2 C1 = initial concentration of original solution V1 = initial volume C2 = final concentration of solution V2 = final volume

Helpful Hints C1 is always greater than C2 V2 is always greater than V1 C units are g/L, g/mL or % V units are mL or L (LOOK AT C units )

Helpful Hints Remember the units of measure must remain the same : g=g, L=L, mL=mL The units for both C’s must be the same The units for both V’s must be the same L to mL (x 1000) mL to L (/1000) 1L = 1000 mL

Template copyright 2005 www.brainybetty.com EXAMPLE We have a solution with an initial concentration of 20 g/L. we dilute it so that its new concentration is 10 g/L and its new volume is 1000 ml. what was its initial volume? C1V1 = C2V2 (20 g/L)(x) = (10 g/L)(1L) x = (10 g/L)(1L) 20 g/L x = 0.5 L or 500 mL 11/8/2018 Template copyright 2005 www.brainybetty.com

Examples Calculate the new concentration if enough water is added to 100mL of 25g/L sodium chloride to make up 1.5L.