Term
In each pair of ionic compounds, which is more likely to have the more negative enthalpy of hydration?
(a) LiCl or CsCl
(b) NaNO3 or Mg(NO3)2
(c) RbCl or NiCl2 |
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Definition
a more negative enthalpy of hydration = takes more energy removed to go from gas to liquid = weaker intermolecular bonds.
(a) LiCl because Li is smaller than Cs and therefore has weaker London forces
(b) Mg(NO3)2 because Mg2+ is a smaller cation than Na+, and also has a greater charge (even smaller)
(c) NiCl2 same as in (b) |
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Term
| ethanol has a vapor pressure of 59mmHg at 25°C. What quantity of energy as heat is required to evaporate 125 mL of the alcohol at 25°C? The enthalpy of vaporization of the alcohol at that temperature is 42.32 kJ/mol. The density is 0.7849 g/mL. |
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Definition
| 90.1 kJ (convert mL to g, g to mol, then multiply by the kJ needed) |
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Term
| What mass of Na2CO3 must you add to 125 g of water to prepare 0.200 m Na2CO3? What is the mole fraction of Na2CO3 in this solution? |
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Definition
0.025 mol --> 2.65 g
3.59e-3
(student solutions manual p. 203) |
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Term
| you wish to prepare an aqueous solution of glycerol, C3H5(OH)3, in which the mole fraction of the solute is 0.093. What mass of glycerol must you add to 425 g of water to make this solution? What is the molality of the solution? |
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Definition
| solve for how many moles of glycerol there are first; you get 2.4, or 220 grams. the molality is 5.7m. (p. 204 SSM) |
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Term
| calculate the enthalpy of solution of LiCl if ΔHf(aqueous) = -445.6 kJ/mol and ΔHf(solid) = -408.7 kJ/mol |
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Definition
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Term
| an unopened soda can has an aqueous CO2 concentration of 0.0506 m at 25C. What is the pressure of CO2 gas in the can? |
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Definition
| 1.49 atm (calculate using mmHg)(SSMp205) |
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Term
| a 35-g sample of ethylene glycol, molmass 62.07, is dissolved in 500.0 g water. The vapor pressure of water at 32C is 35.7mmHg. What is the vapor presssure of the water-ethylene glycol solution at 32C? |
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Definition
| 35.0mmHg (Raoult's law --> Psolution=(molratio)(pure solven equilibrium pressure) |
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Term
| when the vapor pressure of a solvent over a solution is measured at a given temperature, it is observed that the vapor pressure of the solvent over the solution is _________ than the vapor pressure of the pure solvent |
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Definition
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Term
| when the vapor pressure of a solvent over a solution is measured at a given temperature, it is observed that the vapor pressure of the solvent is _________ to the relative number of solvent molecules in the solution. |
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Definition
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Term
| when is the normal boiling point in a liquid? |
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Definition
| when the vapor pressure is equal to 1atm |
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Term
| the boiling point elevation of a solution is directly proportional to ____________ |
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Definition
| the molality of the solute |
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Term
C14H10 is dissolved in 50.0 g of benzene and the boiling point is 80.51C. What mass of the hydrocarbon must have been dissolved?
BP of benzene is 80.10; Kbp for benzene is 253C/m |
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Definition
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Term
| solutions with the _______ number of particles will have the lowest freezing point. |
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Definition
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Term
| an awueous solution containing 1.00 g of bovine insulin per liter has an aosmotic pressure of 3.1 mmHg at 25C. Calculate the molar mass of bovine insulin. |
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Definition
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Term
| what are two properties of colloids? |
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Definition
| large molar mass; large particles |
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Term
| what is the tyndall effect and why do colloids cause it? |
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Definition
| the scattering of visible light in a solvent; because of their large size. |
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Term
| what is the difference between a sol and a gel? |
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Definition
| a sol is a dispersion of solid particles in a liquid; a gel is the same dispersal, but the structure keeps it from being mobile. |
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Term
| how can a stable hydrophobic colloid be made to disperse? |
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Definition
| by introducing ions to disrupt the balance and let the particles interact with each other. |
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Term
| how do emulsifying agents produce a colloid where nonpolar and polar particles mix? |
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Definition
| an emulsifying agent is both polar and nonpolar, so it can interact with both and, by extension, cause the two to interact. |
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Term
| what is the difference between the molecular interactions of gases vs. solids and liquids? |
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Definition
| solid and liquid molecules interact with each other; gaseous molecules don't. |
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Term
| name of an ion surrounded by water vs. surrounded by another solvent: |
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Definition
| hydrated ion vs. complex ion |
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Term
| what two things do the forces of (ionic) attraction depend on, and which is more dominant? |
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Definition
| distance and charge (Coulomb's Law); charge is more dominant. |
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Term
| if one compound has a lower molecular weight than another, you would expect the boiling point to be higher. If it's actually lower, what does that suggest about the substance with the lower molecular weight? |
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Definition
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Term
| polarizability increases with ____________ |
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Definition
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Term
| heavier hydrocarbons will tend towards being [liquid/solid/gas] |
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Definition
| liquids and/or solids (the heavier, the stronger bonding, the "stickier") |
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Term
| interactions between nonpolar molecules get stronger the ____________ they get; between polar molecules, the __________ they get. |
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Definition
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Term
| liquids move __________ than solids but _______ than gasses. |
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Definition
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Term
| liquids have a set ___________ but NOT a set __________ |
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Definition
| liquids have a set volume but not a set shape. |
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Term
| unlike gases, liquids _________ expand to fill their containers. |
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Definition
| liquids do NOT expand to fill their containers. |
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Term
| kinetic energy increases with _________ |
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Definition
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Term
| in order for molecules to evaporate, where in the liquid do they have to be? |
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Definition
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Term
| what is a state of equilibrium? |
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Definition
| when the rate of evaporation in a closed container equals the rate of condensation |
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Term
| what is the equilibrium vapor pressure of a liquid? |
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Definition
| how much pressure it exerts when its molecules are evaporating and condensing at the same rate in a closed container |
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Term
| what are two factors that affect equilibrium vapor pressure of a substance? |
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Definition
| temperature and intermolecular bonds |
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Term
| what equation relates vapor pressure of a substance with temperature? |
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Definition
| the Claussius-Clapeyron Equation |
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Term
| what is the boiling point of any given liquid? |
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Definition
| when its vapor pressure equals outside (usually atmospheric) pressure |
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Term
| how does a butane lighter work? the equilibrium vapor pressure is about 2.4 atm. |
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Definition
| when the lighter is opened, vapor pressure is suddenly greater than atmospheric pressure the liquid boils and lets gas escape, which can then be ignited by a spark |
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Term
| the stronger the intermolecular bonds, the ___________ the boiling point will be |
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Definition
| the stronger the intermolecular bonds, the HIGHER the boiling point will be |
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Term
| why are the molecules at the top of a liquid less stable? |
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Definition
| they are at a higher energy - they're being pulled mostly down towards the middle (not being pulled from all sides) |
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Term
| why does liquid assume a spherical shape? |
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Definition
| it tries to assume the shape with the lowest surface/mass ratio - wants fewer particles in unstable states |
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Term
| why will putting a drop of soap in water decrease surface tension? |
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Definition
| it will disrupt the hydrogen bonds that keep the surface tension so high |
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Term
| how would you make paint spread more easily? |
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Definition
| by reducing the surface tension |
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Term
| what does viscosity depend on? (3) |
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Definition
| temperature (the lower the temperature, the more viscous/resistant to flow); intermolecular forces; the structure of the molecules themselves |
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Term
| how are molecular solids held together? |
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Definition
|
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Term
| what holds together an ionic solid? |
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Definition
|
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Term
| what holds together a metallic solid? |
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Definition
|
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Term
| what holds together a network solid? |
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Definition
| covalent bonds (think diamond) |
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Term
| what is a unit cell/cubic unit cell? |
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Definition
| the smallest square/cubic pattern that repeats itself in a solid |
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Term
| liquid mercury has a vapor pressure of 0.00169 mmHg at 24C. If the air in a small room is saturated with mercury vapor, how many atoms of mercury vapor occur per cubic meter? |
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Definition
| 5.49e19 atoms/m3 (use PV=nRT to find molarity n/V, use that to find atoms) (p.189 SSM) |
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