IN THE NAME OF ALLAH THE MOST GRACIOUS, THE MOST MERCIFUL CHEM 122. LEVEL-2 LECTURE # 1 CHAPTER 8 - SOLUTIONS Chemistry by Timberlake p.226 Presented by: Department Of Chemistry RCDP

Types of mixtures 2- Colloidal solution/dispersion 3-Suspension

1- True solution: It is a homogeneous mixture of two or more substances. One substance which is called the solute is uniformly dispersed in another substance called the solvent. Every part of the solution possesses the same composition, density, viscosity. Example: Sugar in water

Solvent: The component present in larger amount in solution. Solute: The component present in smaller amount in solution (in lesser amount). Solubility: Maximum amount of solute dissolved in a fixed quantity of solvent ( 100g) at a given temperature to form a saturated solution.

TYPES of SOLUTIONS: Three States of matter : SOLID GAS LIQUID

Types of solutions (7): A solution of gas in gas, example air (O2 gas in N2 gas) A solution of gas in liquid, example aerated water such as soda water (CO2 in water) A solution of gas in solid , example hydrogen in palladium (Pd) A solution of liquid in liquid, example Benzene in toluene. A solution of liquid in solid, example Amalgamated zinc (mercury in zinc) A solution of solid in liquid, example seawater (NaCl in water). A solution of solid in solid, Alloys, example Cu in Au (gold) and brass (zinc in copper). Au is gold

gas/gas air O2 gas and N2 gas gas/liquid soda CO2 gas in water Type of solution Example Components of solution gas/gas air O2 gas and N2 gas gas/liquid soda CO2 gas in water solid/liquid seawater NaCl in water solid/solid brass zinc and copper

Properties of solution : It is a homogeneous mixture of two or more substances, where the solute, 1-May spread evenly throughout the solution. 2-Cannot be separated by filtration. 3-Can be separated by evaporation. 4-Is not visible, solution appears transparent 5-May give a color to the solution.

Q1: Identify the element (1), compound (2) or solution (3) : water sugar salt water air tea

Q2- Identify the solute in each of the following solutions: a) 2 g sugar + 100 mL water b) 60.0 mL ethyl alcohol + 30.0 mL of methyl alcohol c) 55.0 mL water + 1.50 g NaCl d) Air: 200 mL O2 + 800 mL N2 e) brass: 20 g zinc + 50 g copper f) 100 g H2O + 5 g KCl

Factors influencing solubility: 1-Temperature: (A) If the formation of solution is endothermic then the solubility increases with the increase in temperature. heat + solute + solution (1) ⇌ solution (2) (B) If the formation of solution is exothermic then solubility decreases with the increase in temperature. gas + solution (1) ⇌ solution (2) + heat Example :Solubility of gases are exothermic. Gases are less soluble at higher temperatures

2-Pressure : Solubility of gases increases with increasing pressure. Henry’s Law: The solubility of a gas in a liquid solution is directly proportional to the pressure of the gas above the solution.

3-Common ion effect: Solubility of AgCl decreases in the solution of NaCl compared to the solubility of AgCl in pure water. This is because of the chloride ion which is a common ion.

Types of solutions according to solute concentration: Saturated solution: Solution contains maximum amount of solute at a given temperature and pressure Unsaturated solution: Solution contains less than the maximum quantity of solute, or if the solution is not saturated. Dilute solution: Quantity of solute is very less in solution.

Types of mixtures(cont.) 2- Colloidal solutions/ dispersions: -These are heterogeneous (non-uniform mixtures.) -In colloidal dispersion, the size of the solute molecules are intermediate between the size of solute molecules in true solution and those in suspension. Range of size 1 to 1000nm Example, Milk, Butter in H2O

Properties of Colloids Have medium size particles, that do not settle out (separate). Particles cannot be filtered (particles are small enough to be pass through filters). Can be separated with semi permeable membranes (particles are too large to pass through semi permeable membranes). Scatter light (Tyndall effect)

Examples of Colloids Fog, clouds (liquid in gas) Whipped cream (gas in liquid) Homogenized Milk (liquid in liquid) Cheese (liquid in solid) Blood plasma (solid in liquid) Pearls (solid in solid)

3- SUSPENSIONS: These are heterogeneous non-uniform mixtures. Properties of Suspensions Have very large particles (can be seen by eye) Settle out Can be filtered Must be stirred to stay suspended N.B: It is important to “Shake well before using” before giving a suspension medication.

Examples of Suspensions Blood platelets Muddy water Calamine lotion

Comparison: (Homogeneous) (Heterogeneous) Solution Colloid Suspension - small particles - intermediate particles - large particles < 1 nm bet. 1-1000 nm >1000 nm - does not separate - does not separate - separates on standing over time over time - cannot be filtered - cannot be filtered - can be filtered (can be separated with semi permeable membranes) - no Tyndall Effect -Tyndall Effect present -Tyndall Effect present - e.g.: salt/H20 - e.g.: milk, gel, smoke, - e.g.: clay/water , foam Italian salad dressing

This is due to the polar and non polar nature of solvent. Polar and non polar solvents: Some substances are soluble in one solvent but not in another solvent. This is due to the polar and non polar nature of solvent. Example: Sugar is soluble in water but not in petrol. Alcohol and water are completely miscible in each other, this is due to the hydrogen bonding. Two non polar substances are miscible (Hexane in Carbon tetrachloride).

Miscible: Fluids that completely dissolve in each other. Non-polar C6H14 will not dissolve in polar H2O. Non-polar C6H14 will dissolve in non-polar CCl4.

“ Like dissolves like ” General rule for solutions is “like dissolves like.” Polar dissolves polar & non-polar dissolves non-polar. Examples: I2 is soluble in CCl4 & relatively insoluble in water NaCl is soluble in water but not in non polar solvents. Polar molecule like CH3OH will dissolve as a molecule in polar H2O. Ionic LiF will dissolve as ions in polar H2O.

Polar solutes dissolve in polar solvents. Solvation and hydration: Polar solutes dissolve in polar solvents. Ionic substances furnish cations (+) and anions ( - ). These ions are surrounded by solvent molecules this is known as solvation and if the solvent is water then it is called hydration. Example NaCl in water.

H2O Hydration Na+ Cl- Na+ Dissolved solute Cl- H2O Na+ Cl- solute

NaCl(s) H2O Na+ (aq)+Cl(aq) When NaCl(s) dissolves in water, the reaction can be written as NaCl(s) H2O Na+ (aq)+Cl(aq) solid separation of ions in water

Q1: Solid LiCl is added to some water. It dissolves because A. The Li+ ions are attracted to the 1) oxygen atom(-) of water 2) hydrogen atom(+) of water B. The Cl- ions are attracted to the

Solid LiCl is added to some water. It dissolves because Answer: Solid LiCl is added to some water. It dissolves because A. The Li+ ions are attracted to the 1) oxygen atom(-) of water B. The Cl- ions are attracted to the 2) hydrogen atom(+) of water

Q2: Like dissolves like A ____________ solvent such as water is needed to dissolve polar solutes such as sugar and ionic solutes such as NaCl. A ___________solvent such as hexane (C6H14) is needed to dissolve nonpolar solutes such as oil or grease.

Q3:Which of the following solutes will dissolve in water? Why? 1) Na2SO4 2) gasoline 3) I2 4) HCl

Answer: 1) Na2SO4 Yes, polar (ionic) 2) gasoline No, nonnpolar 3) I2 No, nonpolar 4) HCl Yes, Polar

Spectator ion: Two ionic compounds NaCl and AgNO3 in water exist as Na+, Cl- and Ag+, (NO3) - ,ions and react with each other Ag+aq + NO3 aq + Na+aq + Cl-aq → AgCl s↓ + Na+aq+ NO3 aq This equation is called ionic equation. In this reaction Na+ and NO3 ions do not change during a reaction are called spectator ions. They are the same before and after the reaction.

Ag+aq + Cl-aq → AgCl↓ ( net ionic equation ) Ag+aq + NO3 aq + Na+aq + Cl-aq → AgCl s↓ + Na+aq+ NO3 aq while writing an ionic equation we can omit the spectator ions. This equation is known as net ionic equation Ag+aq + NO3 aq + Na+aq + Cl-aq → AgCl s↓ + Na+aq+ NO3 aq Ag+aq + Cl-aq → AgCl↓ ( net ionic equation )

Another example: AgF aq + KCl aq → AgCl s +KF aq – molecular equation Ag+aq + F-aq + K+aq + Cl-aq → AgCl ↓ + K+ + F- ---ionic equation Ag+aq + Cl-aq → AgCl ↓ ---net ionic equation

PCDPR-CHEM.122 LEVEL 2 MCQz Q1. Indicate solution among the following: A). Water b) salt-water c) air d) both b & c Q2. Brass is an alloy of 20 g zinc + 50g copper. Identify the solute: A). 20 g zinc b) 50g copper c) both a & b d) none of the above Q3. Identify solvent in 55ml water & 2g NaCl A). 55ml water b) 2g NaCl

Q4.Solubility of gases increases with rise in: A). Pressure b) temperature c) both a &b d) none of the above Q5. The process in which water is taken as solvent is called: A). solvation b) hydration c) evaporation d) condensation

Q6. Iodine I2 is soluble in CCl4: A) True b) False Q7.Polar or ionic solutes are dissolved in: A). Polar solvents b) non Polar solvents c) Polar solutes d) non Polar solutes Q8. Which solute will dissolve in water? A) Na2SO4 b) gasoline c) I2 d) Hexane