SOLUTIONS A homogeneous mixture in which the components
- Slides: 35
SOLUTIONS A homogeneous mixture in which the components are uniformly intermingled
Terms Solvent – The substance present in the largest amount in a solution. The substance that does the dissolving. Solute – The other substance or substances in a solution. The substance that is dissolved.
ELECTROLYTES l l l Substances that break up in water to produce ions. These ions can conduct electric current Examples: Acids, Bases and Salts (ionic compounds)
SOLUBILITY l “Like dissolves Like” – – Polar molecules dissolve polar molecules Nonpolar molecules dissolve nonpolar molecules
SOLUBILITY RULES l l l All common salts of Group I elements and ammonium are soluble All common acetates and nitrates are soluble All binary compounds of Group 7 with metals are soluble except those of silver, mercury I and lead All sulfates are soluble except those of barium, strontium, calcium, silver, mercury I and lead Except for those in Rule 1, carbonates, hydroxides, sulfides and phosphates are insoluble
Terms l Saturated – l Unsaturated – l When the solution contains more solute than a saturated solution will hold at that temperature Concentrated – l When a solvent can dissolve more solute Supersaturated – l When a solution contains the maximum amount of solute When a relatively large amount of solute is dissolved Dilute – When a relatively small amount of solute is dissolved
Factors Affecting the Rate of Dissolution l Surface Area l Stirring l Temperature
Temperature vs Solubility
MOLARITY l Molarity-the number of moles of solute per liters of solution l M = molarity = moles of solute liter of solution
l Calculate the molarity of a solution prepared by dissolving 11. 5 g of Na. OH in enough water to make a 1. 50 L solution.
l Calculate the molarity of a solution prepared by dissolving 1. 56 g of HCl into enough water to make 26. 8 ml of solution.
l Calculate the number of grams of sodium phosphate required to make 150. ml of a 2. 5 M solution.
l How many liters of solution are needed to dissolve 5. 0 g of hydrochloric acid to make a 3. 0 M hydrochloric acid solution?
l What is the concentration of each ion in a 0. 50 M solution of Co(NO 3)2? l What is the concentration of each ion in a 0. 25 M solution of aluminum sulfate?
l How many moles of Ag+ ions are present in 25. 0 ml of a 0. 75 M Ag. NO 3 solution? l Calculate the number of moles of Cl- ions in 1. 75 L of 1. 0 x 10 -3 M Al. Cl 3
l To analyze the alcohol content of a certain wine, a chemist needs 1. 00 L of an aqueous 0. 200 M K 2 Cr 2 O 7 (molar mass is 294. 2 g/mol) How much K 2 Cr 2 O 7 must be weighed out to make this solution?
DILUTIONS l M 1 x V 1 = M 2 x V 2 l What volume of 16 M sulfuric acid must be used to prepare 1. 5 L of a 0. 10 M H 2 SO 4 l What volume of 12 M HCl must be used to prepare 0. 75 L of a 0. 25 M HCl?
l When barium nitrate and potassium chromate react in aqueous solution, the yellow solid barium chromate is formed. Calculate the mass of barium chromate that forms when 3. 50 x 10 -3 mole of solid barium nitrate is dissolved in 265 ml of 0. 0100 M potassium chromate solution.
MOLALITY l A unit of concentration equal to the number of moles of solute per kilogram of solvent m = moles of solute kg solvent
l 98. 0 g Rb. Br in 824 g water l 85. 2 g Sn. Br 2 in 1. 40 x 102 g water
Phase Change Diagram
Definition l Boiling Point – when the vapor pressure of the liquid is equal to the atmospheric pressure
Freezing Point Depression/ Boiling Point Elevation l Colligative property – a solution property that depends on the number of solute particles present (ie – f. p. and b. p. ) – – Freezing Point Depression Boiling Point Elevation
Calculating Boiling Points l Kbp = boiling point constant – – Water 0. 515 OCkg/mol 1 mole of a solute particle will raise the bp of 1 kg of water by 0. 515 OC l 1 m solution of sugar water 1(0. 515 OC) 100. 515 OC l 1 m solution of Na. Cl water 2(0. 515 OC) 101. 03 OC l 1 m solution of Ca. Cl 2 water 3(0. 515 OC) 101. 545 OC
Calculating Freezing Points l Kfp = freezing point constant – – Water 1. 853 OCkg/mol 1 mole of a solute particle will lower the fp of 1 kg of water by 1. 853 OC l 1 m solution of sugar water 1(1. 853 OC) -1. 853 OC l 1 m solution of Na. Cl water 2(1. 853 OC) -3. 706 OC l 1 m solution of Ca. Cl 2 water 3(1. 853 OC) -5. 559 OC
l l l ΔTfp = im Kfp = 1. 853 o. Ckg/mol ΔTbp = im Kbp = 0. 515 o. Ckg/mol If 26. 4 grams of nickel II bromide are dissolved in 224 grams of water, what will be the new boiling point and freezing point of the resulting solution?
l If 25. 0 grams of calcium chloride are dissolved in 500 grams of water, what will be the new boiling point and freezing point of the resulting solution?
MASS PERCENT l A unit of concentration equal to the mass of solute per mass of solution part x 100 whole
l A solution is prepared by mixing 1. 00 g of ethanol with 100. 0 g of water. Calculate the mass percent of ethanol in this solution. l A 135 g sample of seawater is evaporated to dryness, leaving 4. 73 g of salt. Calculate the mass percent of salt in the saltwater.
1. Molarity (M) = 2. Mass (weight) percent = 3. Mole fraction ( A) = 4. Molality (m) =
Sol’n is prepared by adding 5. 84 g of formaldehyde (H 2 CO) to 100. 0 g water. Final vol of solution is 104. 0 m. L. Calculate the molarity, molality, mass % and .
M = 1. 87 M H 2 CO m = 1. 94 m H 2 CO Mass %= 5. 52 % H 2 CO =. 0338
Molecular Mass Determination l l If 99. 0 g of a nonionizing solute dissolved in 669 grams of water and the freezing point of the resulting solution is -0. 960 o. C, what is the molecular mass of the solute? ΔTfp = im Kfp m = ΔTfp Kfp
l l If 64. 3 g of a nonionizing solute dissolved in 390. grams of water and the boiling point of the resulting solution is 100. 680 o. C, what is the molecular mass of the solute? ΔTbp = im Kbp m = ΔTbp Kbp
Anthraquinone contains only carbon, hydrogen and oxygen and has an empirical formula of C 7 H 4 O. When 15. 93 g of anthraquinone are added to 1 kg of water the freezing point depression was determined to be 0. 240 o. C. Calculate the molar mass of the biomolecule (Kf for chloroform is 4. 70 o. Ckg/mol)
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