 # Concentration/Dilution

## Presentation on theme: "Concentration/Dilution"— Presentation transcript:

Concentration/Dilution

Solution Preparation Preparing a solution of Sodium Chloride (NaCl)
Solute= Sodium Chloride (solid) Solvent = water (distilled) We know that we define solutions based on CONCENTRATION (Molarity) Molarity (M) - the number of moles of solute dissolved in a certain volume of the total solution. (mol/L)

Solution Preparation 0.500L x 0.25 mol 0.25mol = 0.25 mol/L 1 L
Preparing Solution preparing a 500ml of a 0.25mol of NaCl solution need to calculate how many grams of NaCl we need for the solution 0.500L x 0.25 mol 0.25mol = 0.25 mol/L 1 L 500mL x L =0.125 mol NaCl 1000mL = 0.500L 0.125 mol x 58.43g 1 mol = 7.304g of NaCl

In Lab you need these materials
sodium chloride scoop scale glass stir rod distilled water volumetric flask

Making Up a Standard Solution
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Prepare a 250mL of a 0.500mol/L solution of Sodium Chloride
Step #1: Determine the mass of Sodium Chloride required

Prepare a 250mL of a 0.500mol/L solution of Sodium Chloride
Step 2: place the amount in a 250mL volumetric flask. If difficult add the amount to a beaker. Step 3: Distilled water is added until the flak is about half full. Step 4: The flask is shaken until the solid has completely dissolved Step 5: Distilled water is again added until the flask is full to the mark.

Calculating the Percent Concentration.
Volume Percentage (% V/V) Used for solutions of a liquid in a liquid Volume % of solute = Volume of solute Examples: Percentage of acetic acid in vinegar Percentage of alcohol in beer and spirits x 100% volume of solution

Calculating the Percent Concentration.
Mass Percentage (% m/m) Used for solid solutions --> alloys Mass % of solute = mass of solute Examples: Percentage of copper in brass Iron in stainless steel or silver x 100% mass of solute & solvent

Calculating the Percent Concentration.
Weight volume Percentage (% m/v) Usually used in household products when a mass of a solute is dissolved in the solvent which is a liquid. Mass volume % = weight of solute(g) Examples: Percentage of caffeine in a cup of tea x 100% volume of solvent (mL)

Dilution Dilution: increasing the amount of solvent and the concentration decreases. common way to take a stock solution & create other solutions. c = n remains constant V decreases (b/c volume increases) increases (b/c water is added)

Dilution During a dilution, the concentration of a solution decreases due to an increase of its volume. The amount of solute remains unchanged Dilution Equation CiVi = CfVf

Dilution Calculate the volume of a 0.10M solution made from 200mL of 0.30M NiCl2 CiVi = CfVf

Add 400mL of water ---to finally end up with 600mL Solution
Dilution Calculate the volume of a 0.10M solution made from 200mL of 0.30M NiCl2 CiVi = CfVf Add 400mL of water ---to finally end up with 600mL Solution