Concentration, Preparation of Solutions PDF

# Concentration, Preparation of Solutions ## Solutions Solutions are homogenous mixtures. ### Components of Solutions: - **Solvent:** the dissolving medium - Often is liquid, frequently water - Can be a gas in air and other gas solutions - Rarely a solid - **Solute(s):** the dissolved...

# Concentration, Preparation of Solutions ## Solutions Solutions are homogenous mixtures. ### Components of Solutions: - **Solvent:** the dissolving medium - Often is liquid, frequently water - Can be a gas in air and other gas solutions - Rarely a solid - **Solute(s):** the dissolved material - Can be solids, liquids, and/or gases - Often more than one solute ## Introduction - A solution is a homogeneous mixture created by dissolving one or more solutes in a solvent. - The chemical present in a smaller amount, the solute, is soluble in the solvent (the chemical present in a larger amount). - They form aqueous solutions. - Water is one of the best solvents for dissolving ionic substances. - Water is a poor solvent for non-polar covalent substances. ## Solution Concentrations - **Dilute:** Small amount of solute for a given solvent - **Concentrated:** Large amount of solute for a given solvent - **Saturated:** Maximum amount of solute for a given solvent - However; these terms are qualitative, not quantitative, and are open to interpretation. ## Percent Concentration - This is the amount of a solute present in per 100 part of solution: - **Weight percent (w/w%):** - Defined as a number of grams of solute present in 100 grams of solution. - Expressed as (w/w%) = weight of the solute (g)/ weight of the solution (g) X100%. - **Volume percent (v/v%):** - Defined as the volume of the solute in ml dissolved in 100 ml of solution as a liquid. - Expressed as (v/v%) = volume of the solute (ml)/ volume of the solution (ml) X100%. - Used when the solution is made by mixing two liquids. - For example, 70% ethanol is prepared by dissolving 70 ml of ethanol in 100 ml of solution. - **Weight/volume percent (w/v%):** - Defined as the amount of solute in grams present in 100ml of solution as a liquid. - Expressed as (w/v%) = weight of solute (g)/ volume of solution (ml) X100% - Example: 0.9% w/v NaCl saline solution is prepared by dissolving 0.9 g in 100 ml saline solution. - Concentration = quantity of the solute / quantity of preparation - **Example:** 10 g of substance B have been dissolved in water, and the volume is completed with water to 200 ml. Calculate the concentration of B in the following terms: g/L, mg/L, µg/ml, ng/ml and pg/µL? ## Parts per Million (ppm) - Parts per million (ppm) represents the number of parts of solute in 10^6 parts of preparation. - ppm= (grams of solute/ parts of the preparation) X 10^6 - **(weight in-volume) ppm:** (grams of solute/ ml of 10^6 parts of the solution) - **(weight in-weight) ppm:** (grams of solute/ g of 10^6 parts of the solution) - **(volume-in volume):** (ml of solute/ ml of 10^6 parts of the solution) - Parts per million (ppm) expresses the number of parts of solute in 10^6 of the solution. - This unit is used to express very small amounts of solute. - **Example:** Prepare 1000 ppm solutions of NaOH: - 1 ppm = 1mg per liter of solution - 1000 ppm = 1000 mg - 1000 mg = 1 gram - 1 gram = 1000 ppm ## Methodology (Materials and Methods) - **Materials:** - Sensitive Balance - Glass Rod - Baker - Volumetric - Washing Bottle - **Method:** Weigh 1 g of NaOH and dissolve it in 1 liter of solvent to prepare 1 liter of 1000 ppm NaOH. ## Discussion - **What is the difference between distilled water and deionized water?** - **Classify solutions according to the amount of solute.**