Lesson 1.5 Preparing Solutions PDF

Unit #1: What determines chemical change? Lesson 5: Preparing Solutions YOSRA SAAD 1  MYP5 Chemistry Unit #1: What determines chemical change? Key Concept Change Related Concepts Transfer, Movement Global Context Orient...

Unit #1: What determines chemical change? Lesson 5: Preparing Solutions YOSRA SAAD 1  MYP5 Chemistry Unit #1: What determines chemical change? Key Concept Change Related Concepts Transfer, Movement Global Context Orientation in time and space Physical and chemical changes require the transfer of kinetic Statement of energy between particles of matter over time, affecting the Inquiry space they occupy. YOSRA SAAD 2 Solutions Solutions are homogeneous mixtures of two or more components. Each solution consists of a solvent and one or more solutes. The solvent is usually the major component of the solution, so the properties of the whole solution are similar to the properties of the solvent. Aqueous solutions are solutions in which the solvent is water. YOSRA SAAD 3 Solutions and concentration A concentrated solution contains a large proportion of solute, and so has a high ratio of solute to solvent. Generally, it refers to solutions with much more than 10 g of the solute per 100 g of the solvent. A dilute solution has a small proportion of solute, and so has a low ratio of solute to solvent. YOSRA SAAD 4 Which solution contains the most particles per cm3? YOSRA SAAD 5 Practice Calculate mass concentration of a solution, where 4.5 g of NaOH is dissolved in 500 cm3 the solution. Mass concentration = 4.5/500 = 0.009 g cm–3 YOSRA SAAD 6 Molar Concentration (Molarity) Molar concentration, c, also known as molarity, is moles of solute per dm3 of the solution. The most common unit is mol dm-3. This is also known as mol/L or M (molar). YOSRA SAAD 7 What is a standard solution? Stock solutions with a known concentration of the solute are called standard solutions. How To Prepare Solutions - YouTube YOSRA SAAD 8 Technique: Making a standard solution 9 N A M E T H E S E P I E C E S O F E Q U I P M E N T. YOSRA SAAD 10 Practice question A 280.0 cm3 standard solution of potassium hydrogen phthalate, C8H5KO4, was made by dissolving 0.430 g in distilled water. a. Calculate the concentration of this solution in mol dm-3. b. Outline how you would dilute this standard solution by a factor of 10 to make a 100 cm3 solution. c. State 2 pieces of precise equipment that would be required for this dilution. 11 Dilution It is a common practice to store chemicals in the form of concentrated solutions (so-called stock solutions) and dilute them to the required concentration when needed. Dilution Formula C1 V1 = C2 V2 How to Dilute a Solution YOSRA SAAD 12 Example 1. A standard solution was prepared by dissolving 6.624 g of sodium carbonate, Na2CO3, in deionized water using a 250cm3 volumetric flask. Calculate the concentration, in mol dm-3, of this solution. 2. An analytical pipette was used to transfer 10.0cm3 sample of this solution to a 100 cm3 volumetric flask, and the flask was topped up to the graduation mark with deionized water. Calculate the concentration, in mol dm–3, of sodium carbonate in the new solution. YOSRA SAAD 13 Serial Dilutions A serial dilution is a series of dilutions of a standard solution, where the concentration is reduced by a fixed amount at each step. Used to form a standard in a technique known as ultraviolet spectroscopy. YOSRA SAAD 14