Chemistry Test Test Questions – Flashcards
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Explain the difference between intramolecular and intermolecular forces.
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inter- attraction between 2 molecules. intra- attraction between atoms in molecules.
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Describe the relationship between the polarity of individual molecules and the nature and strength of intermolecular forces.
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the more polar the molecule, the stronger the IMF.
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On the molecular level, describe dipole-dipole intermolecular forces.
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the "+" end of a polar molecule is attracted to the "-" end of a nearby molecule.
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Describe the relationship between molecular size and the strength of London dispersion forces.
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the larger the molecule, the stronger the force.
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What effect do intermolecular forces have on the boiling point of a liquid?
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the stronger the IMF, the higher the boiling point.
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Suggest an explanation for the fact that, at room temperature, carbon dioxide is a gas while silicon dioxide is a solid.
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both are linear, nonpolar molecules, but CO₂ is smaller that SiO₂.
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Ionic solids typically have melting points hundreds of degrees higher than the melting point of molecular solids. Explain.
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Ionic bonds (intramolecular forces) are much stronger than covalent bonds.
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Although methane, CH₄, and ammonia, NH₃, differ in molar mass by only one unit, the boiling point of ammonia is over 100˚C higher than that of methane. Explain.
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NH₃ has H-bonding, while CH₄ does not. CH₄ has London dispersion forces.
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Explain the reasons for the difference in boiling points between HF (20˚C) and HCl (-85˚C)
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HF (20˚C) is H-bonding. HCl (-85˚C) is dipole-dipole. H-bonding > dipole-dipole.
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Explain the reasons for the difference in boiling points between HCl (-85˚C) and LiCl (1360˚C)
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HCl (-85˚C) is dipole-dipole. LiCl (1360˚C) is an ionic compound. ionic compound > dipole-dipole.
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Explain the reasons for the difference in boiling points between CH3OCH3 (-24˚C) and CH3CH2OH (79˚C)
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CH3OCH3 (-24˚C) is dipole-dipole. CH3CH2OH (79˚C) is H-Bonding. H-Bonding > Dipole- Dipole.
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Explain the reasons for the difference in boiling points between C2H6 (-89˚C) and C8H18 (126˚C)
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C2H6 (-89˚C) is LDF. C8H18 (126˚C) is LDF. Although both are LDF, C2H6 has a molar mass of 18g, while C8H18 has a molar mass of 114g. Higher Boiling Point = larger mass.
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What is the relationship between boiling point, external pressure and vapor pressure?
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more pressure = higher boiling point.
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choose the liquid that would have the higher vapor pressure: CH3OCH3 or CH3CH2OH. Explain Why.
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CH3OCH3 has higher vapor pressure. CH3OCH3 is dipole-dipole. CH3CH2OH is H-Bonding. Dipole-Dipole has less IMF.
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choose the liquid that would have the higher vapor pressure: HF or HCl. Explain Why.
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HCl has higher vapor pressure. HF is H-bonding. HCI is Dipole-Dipole.
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choose the liquid that would have the higher vapor pressure: Hg or Br2. Explain Why.
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Br2 has higher vapor pressure. Hg is LDF. Br2 is LDF. Br2 has smaller mass, so less IMF
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What is the relationship between kinetic energy and temperature?
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as temperature goes up, so does kinetic energy.
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Explain why liquids cool as evaporation takes place.
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as a liquid changes to a gas, it absorbs energy from its surroundings resulting in cooling.
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How can water be made to boil at room temperature?
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by lowering the external pressure.
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What are two factors that determine the arrangement of ions in an ionic crystal?
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the charge and the relative size.
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determine what type of solid each substance is and EXPLAIN: lithium.
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There is one element so ATOMIC SOLID.
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determine what type of solid each substance is and EXPLAIN: carbon tetrachloride.
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There are two nonmetals so MOLECULAR SOLID.
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determine what type of solid each substance is and EXPLAIN: sodium iodide.
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There is a nonmetal and a metal so IONIC SOLID.
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determine what type of solid each substance is and EXPLAIN: lead.
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There is one element so ATOMIC SOLID.
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determine what type of solid each substance is and EXPLAIN: calcium oxide.
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There is a nonmetal and a metal so IONIC SOLID.
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determine what type of solid each substance is and EXPLAIN: dry ice (CO2)
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There are two nonmetals so MOLECULAR SOLID.
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Describe a saturated solution.
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a solution that has as much solute are will dissolve at that temperature and for that amount of solvent. (on curve)
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Describe an unsaturated solution.
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a solution that has not reached the limit of solute that will dissolve in it. (under curve)
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Describe a supersaturated solution.
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a solution that contains more dissolved solute than a saturated solution at that temperature and for that amount of solvent. (above curve)
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Discuss the factors that affect the rate of dissolving.
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1. increase surface area (liquid) 2. stirring 3. increase temperature of solvent (if ionic solid- not if a gas)
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What is a molarity?
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Molarity is moles of solute/liters of solution.
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What is a colligative property?
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a property that depends on the concentration of solute particles, not identity.
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How does adding a solute to a liquid affect the liquid's vapor pressure? freezing point? boiling point?
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vapor pressure decreases. boiling point increases. freezing point decreases.
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Adding which of the following to 1.0 L of water would result in a solution with the lowest freezing temperature? a) 1.0 mol KCl b) 100.0 g NaCl c) 2.0 mol of sugar (C12H22O11) d) 100.0 g KCl
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100.0 g NaCl
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Describe the process of solvation.
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ions are pulled away from crystal by the opposite charged side of the water molecule and then surrounded by water molecule
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What is melting?
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the change from solid to liquid.
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What is freezing?
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the change from liquid to solid
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What is vaporization?
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the change from liquid to gas.
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What is evaporation?
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vaporization from the surface of a liquid.
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What is boiling?
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vaporization throughout a liquid.
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What is condensation?
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that change from gas to liquid.
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What is sublimation?
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the change from solid directly to gas.
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What is deposition?
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the change from gas directly to a solid.
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What is a solid?
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matter than has definite volume and shape. molecules are packed together tightly and move slowly. they vibrate about a fixed point.
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What is a liquid?
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matter that has definite volume but indefinite shape. molecules are loosely packed, and move with speed. it can flow and take any shape of the container.
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What is a gas?
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matter that has indefinite volume and shape. loosely arranged and have very rapid and chaotic movement. a gas can take on the size and shape of the container.
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What is the kinetic theory of matter?
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molecules are always moving.
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What piece of glassware is needed to prepare solutions of exact concentration?
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volumetric flask
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How would you read a label that says 8M HCL?
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8 molar HCL
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Rank the following from lowest to highest anticipated boiling point. : C₂H₄, CH₄, Ne, H₃COCH₃.
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Ne, CH₄, C₂H₄, H₃COCH₃
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Define Surface Tension.
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Liquids tendency to quire the least surface area possible.
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Define Volatility.
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the tendency of a substance to vaporize.
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Define Viscosity.
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a liquid's resistance to flow.
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Write a statement relating to the viscosity of a substance to the strength of its intermolecular forces.
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the greater the viscosity the greater the strength.
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Write a statement relating to the volatility of a liquid to the strength of its intermolecular forces.
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the more volatility the weaker the substance.
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Write a statement relating to the surface tension of a liquid to the strength of its intermolecular forces.
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the greater the strength of the intermolecular force the greater the surface tension.
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Which substance in each pair would be expected to be more volatile at a particular temperature? H₂0 or H₂S Explain.
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H₂0 because IMF of H₂0 is weaker.
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Which substance in each pair would be expected to be more volatile at a particular temperature? H₂0 or CH₃OH Explain.
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CH₃OH because IMF of CH₃OH is weaker.
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Which substance in each pair would be expected to be more volatile at a particular temperature? CH₃OH or CH₃CH₂OH Explain.
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CH₃OH because IMF of CH₃OH is weaker.
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Describe, on a microscopic basis, the process of evaporation and condensation.
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Evaporation is when liquid molecules change to gas molecules. Condensation is when gas molecules change to liquid molecules.
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Define crystalline solid.
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repeating arrangement of component species in a solid.
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Define dipole-dipole interactions.
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lining up of opposite charges on adjacent polar molecules.
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Define equilibrium vapor pressure.
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maximum pressure of vapor that builds up in a closed container.
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Define ionic solids.
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solids that melt at relatively high temperatures.
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Define London dispersion forces.
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instantaneous dipole forces for nonpolar molecules.
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Define molecular solids.
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solids that melt at relatively low temperatures.
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What type of solid is CaCO₃?
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ionic
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What type of solid is I₂?
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molecular
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What type of solid is SiO₂?
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molecular
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What type of solid is Ag?
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atomic
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What type of solid is Nh₄NO₃?
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ionic
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What is a homogenous mixture called?
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A Solution.
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What is an example of a homogenous mixture?
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Salt water.
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In a solution, what is the substance present in the largest amount called?
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A Solvent.
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In a solution, what is the substance present in the smallest amount called?
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A Solute.
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Unlike a substance, a solution has a ______ composition.
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uniform
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What are the three factors that affect the rate of dissolution?
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temperature, distance, and atomic weight.
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define the relationship between IMF and vapor pressure.
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lower IMF = higher vapor pressure
