Exambusters Study Cards 13 Solutions

 Molarity (State general equation)
 The number of moles of solute in a liter of solution.   M=n/L   M= molarity; n = moles; L = liters
 Solute
 The substance dissolved in another (solvent). Salt is the solute in salt water.
 Solvent
 A substance, usually a liquid, into which another substance (solute) is dissolved. Water is the solvent in iced tea.
 Solution (Give an example)
 A liquid, gas, or solid phase containing two or more components uniformly dispersed.   e.g. air, coffee, saltwater
 Calculate the molarity when 5 moles of NaCl is dissolved in 25 liters of water.
 M = n/L   M = 5/25 M = 0.2M
 Calculate the moles of NaCl in 5 liters of a 2 molar solution.
 M = n/L 2 M = n/5 L 10 = moles of NaCl
 Acid anhydride
 Non-metallic oxides which, when reacted with water, form acid solutions. e.g. CO2 + H2O → H2CO3 SO3 + H2O → H2SO4
 Basic anhydride
 Metallic oxides which, when reacted with water, form basic solutions. e.g. Na2O + H2O → 2 NaOH CaO + H2O → Ca(OH)2
 Why is water a good solvent for ionic compounds?
 Due to hydrogen bonding, water is polar. The negatively charged oxygen attracts a cation, and the positively charged hydrogen, an anion.
 Solubility Curves
 A curve for a given substance which shows how much dissolves in a given amount of solvent at different temperatures.
 How do temperature and pressure affect the solubility of a solid?
 Solubility usually increases with increasing temperature. Pressure has little effect.
 How do temperature and pressure affect the solubility of a gas?
 Solubility usually decreases with increasing temperature. Solubility in creases in direct proportion to an increase in pressure.
 Which three factors affect the rate of solubility?
 pulverizing stirring heating
 What is a general rule for solubilities of polar and nonpolar compounds?
 “Like dissolves like.” Ionic and polar solvents dissolve ionic, polar solutes. e.g. Water dissolves salt.   Nonpolar solvents dissolve nonpolar solutes. e.g. Acetone dissolves gasoline and cooing oil.
 Solubility of nitrates, acetates, and chlorates in water.
 All are soluble
 Solubility of Na, K, and (NH4)+ compounds in water.
 All are soluble.
 Solubility of chlorides in water.
 All chlorides are soluble, except Ag, Hg, Pb.
 Solubility of sulfates in water.
 All sulfates are soluble, except Pb, Ba, Sr, Ca
 Solubility of carbonates, phosphates, sulfides, and silicates in water.
 All insoluble, except Na, K, (NH4)+
 Solubility of hydroxides (OH-) in water.
 All insoluble except Na, K, (NH4)+, Ca, Ba, Sr
 Hydrated ion
 A dissolved ion which is surrounded by water molecules. It is attracted electrostatically to the polar water molecule.
 Miscible
 Two liquids which dissolve in each other. e.g. water and alcohol
 Immiscible
 Two liquids which do not dissolve in each other. e.g. oil and vinegar
 Brownian Movement
 When light is shone through a colloid, the individual zig-zag paths of the particles in the dispersing medium can be observed; like smoke in a dark theater.
 particle size less than 1 nanometer.  Clear (may be colored) )articles don’t settle Can pass through membranes Particles not visible
 particles measure 1-1000 nanometers Particles don’t pass through a membrane Show Brownian movement and the Tyndall effect Particles don’t settle Clear Pass through filter paper
 No Brownian movement Don’t pass through filter paper or a memebrane Cloudy, but particles settle on standing Particles visible with microscope or eye
 Dilute
 Small amount of solute in the solvent.
 Concentrated
 Large amount of solute in the solvent.
 Saturated
 In the presence of undissolved solute, the solution is holding all the solute possible at that temperature.
 Unsaturated
 More solute can be dissolved in the solvent at that temperature.
 Supersaturated
 Created by cooling a saturated solution. If cooled slowly, the solute stays dissolved. The amount of solute in the solution is greater than the solubility at a given temperature.
 Write the equation for percent concentration of a solute in a solution (mass/mass).
 % concentration = (gsolute/gsolution)(100%)
 HOw many grams of NaCl are required to prepare 500 g of a 5% solution?
 % Conc. = (gNaCl/gsolution)(100%) 5% = (x/500 g)(100%) 25 g NaCl = x
 Molality
 The number of moles of solute dissolved in 1 kg of solvent. molality (m) = moles solute/kg solvent
 Calculate the molality of 10 moles of H2SO4 dissolved in 4 kg of water.
 molality = moles solute/kg solvent = 10/4 = 2.5 molal
 Gram-equivalent weight
 The amount of substance which reacts with or displaces one mole of H+ ions.
 Normality
 The number of gram-equivalent weights in a liter of solution.
 Wire the equation for molarity changes related to diluting a solution.
 (M1)(V1)= (M2)(V2)   M = molarity V = Volume
 10 liters of a 6 molar solution is diluted to 3 molar. What is the final volume?
 (M1)(V1)= (M2)(V2) (6)(10) = (3) (V2) V2 = 20 L
 Colligative Properties
 Properties of solutions that depend primarily on the concentration of solute and not on the type of particle.
 List three basic colligative properties of solutions.
 vapor pressure lowering boiling point elevation freezing point depression
 In H2O solutions how many °C is the freezing point depressed for each molal of solute?
 1.86 °C for each molal of particles of solute
 In H2O solutions how many °C is the boiling point elevated for each molal of solute?
 0.51 °C for each molal of particles of solute
 Hydrated crystal
 A crystal that holds a definite proportion of water in its structure
 Crystal
 In a crystal structure, ions or atoms form a repeating pattern of unit cells.
 List six basic types of unit cells which can make up crystal lattices.
 Simple cubic face-centered cubic body-centered cubic tetragonal hexagonal monoclinic
 efflorescent
 Hydrated crystals which lose their water of hydration on exposure to air at room temperature. e.g. magnesium sulfate
 deliquescent
 Hydrated crystals which absorb water from the air and become wet. e.g. calcium chloride and magnesium chloride
 anhydrous crystal
 A hydrated crystal which loses its water of hydration. The pure salt loses the crystal structure and crumbles to powder
 Unit cell
 The smallest portion of a crystal lattice that is repeated throughout the crystal
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