Module 4 Structure of Crystalline and Amorphous Solids Flashcards
What type of solid has a definite internal crystal structure?
Crystalline
Amorphous
Ceramic
Network
Crystalline
Explain why a crystalline substance is defined by its particles being arranged in a highly ordered, repeating pattern.
-This arrangement allows for maximum randomness in particle positioning.
-It results in a sharp melting point due to uniform intermolecular forces.
-The structure leads to irregular shapes and varied physical properties.
-It causes the substance to melt over a broad temperature range
It results in a sharp melting point due to uniform intermolecular forces.
Which characteristic best explains why this newly discovered mineral is classified as crystalline? It possesses a highly ordered internal structure, sharp, well-defined faces, a distinct melting point, and the ability to break cleanly along specific planes when cleaved.
-It has an irregular shape
-It melts over a wide temperature range
-Its particles are arranged in a regular repeating pattern
-It does not conduct electricity
-Its particles are arranged in a regular repeating pattern
A sample of 0.892 g of potassium chloride (KCl) is dissolved in 54.6 g of water. What is the percent by mass of KCl in the solution.
4.61%
3.61%
2.61%
1.61%
1.61%
How is molarity defined?
Moles per kilogram solvent
Mass per liter solvent
Moles per liter solution.
Moles per density.
Moles per liter solution.
Percent by mass is a useful way to express the concentration of a solution because it allows for a direct comparison of different solutes dissolved in the same solvent, regardless of their chemical properties. Since it is based on mass rather than volume, it remains consistent even if temperature or pressure changes, making it a reliable measure for comparing solutions.
-It accounts for differences in density between solvents
-It provides a direct comparison based on mass ratios.
-It is only applicable to aqueous solutions
-It does not account for molecular weight differences.
-It provides a direct comparison based on mass ratios.
Mole fraction is a valuable measure for understanding the composition of mixtures, particularly for gases and volatile liquids, because it expresses the relative number of moles of each component. Since it is independent of temperature and pressure, it provides a consistent way to compare different substances in a mixture, making it especially useful in applications like gas laws and vapor pressure calculations.
-By providing information about volume ratios.
-By giving insight into molecular interactions through relative moles
-By measuring density changes directly
-It does not account for molecular weight differences.
-By giving insight into molecular interactions through relative moles
Percent by volume (% v/v) is a useful way to express the concentration of liquid solutions, particularly in industries like beverages, because it directly reflects the proportion of one liquid component relative to the total solution. Since liquids mix based on volume rather than mass, this measurement provides a clear and practical way to standardize formulations, ensuring consistency in products like alcoholic beverages, perfumes, and pharmaceuticals.
-It accounts for changes in density between solutes and solvents
-It provides a straightforward way to calculate concentrations based on easily measurable volumes
-It is primarily used for gases rather than liquids due to differences in mixing behaviors
-It requires precise mass measurements, making it impractical for many applications
-It provides a straightforward way to calculate concentrations based on easily measurable volumes
How does an increase in solution concentration impact its boiling point?
-It decreases the boiling point
-It has no effect on the boiling point
-It increases the boiling point.
-The effect depends on the solute’s identity
-It increases the boiling point.
How does increasing the concentration of a non-volatile solute affect the vapor pressure of a solvent?
-Vapor pressure remains constant regardless of changes in solution composition
-Vapor pressure increases due to increased molecular interactions at higher concentrations.
-Vapor pressure decreases because fewer solvent molecules reach equilibrium at higher concentrations
-The change depends entirely on whether it’s an aqueous or non-aqueous solvent
-Vapor pressure decreases because fewer solvent molecules reach equilibrium at higher concentrations
Explain why the van’t Hoff factor (i) is generally greater than 1 for electrolyte solutions but close to 1 for nonelectrolyte solutions.
-Electrolytes have lower molar masses
-Electrolytes dissociate into ions in solution, increasing the number of solute particles
-Nonelectrolytes are always insoluble
-Nonelectrolytes react with the solvent.
Electrolytes dissociate into ions in solution, increasing the number of solute particles
Compare the expected vapor pressure lowering of a 0.1 m MgCl₂ solution to that of a 0.1 m urea solution, highlighting the differences between the two.
-The vapor pressure lowering will be approximately the same for both solutions
-The vapor pressure lowering for MgCl2 will be about three times greater than for urea.
-The vapor pressure lowering for urea will be significantly greater than for MgCl2 because urea has a higher molar mass
-The vapor pressure lowering for MgCl2 will be less than for urea because MgCl2 is more soluble
The vapor pressure lowering for MgCl2 will be about three times greater than for urea.
Compare the freezing point depression (ΔTf) of a 0.1 m NaCl solution to that of a 0.1 m glucose solution?
-The ΔTf of NaCl is approximately half that of glucose
-The ΔTf of NaCl is approximately twice that of glucose.
-The ΔTf of NaCl is approximately the same as that of glucose
-The ΔTf of NaCl is zero.
-The ΔTf of NaCl is approximately twice that of glucose.
How does increasing the concentration of a solution affect its osmotic pressure?
-It decreases the osmotic pressure
-It has no effect on osmotic pressure
-It increases the osmotic pressure.
-The effect depends on temperature
It increases the osmotic pressure.
Why is molarity commonly favored over molality for preparing solutions in laboratory settings?
-Because it accounts for changes in temperature affecting volume.
-Because precise volumes are easier to measure and control than masses.
-Because it provides a more accurate concentration measurement at high temperatures
-Because it involves fewer calculations compared to molality
-Because precise volumes are easier to measure and control than masses.
Zinc reacts with HCl to produce ZnCl2 and hydrogen gas H2. Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) How many liters of a 1.50 M HCl solution completely react with 5.32 g of zinc?
0.408 L
0.308 L
0.208 L
0.108 L
0.108 L
Ethylene glycol (EG), CH₂(OH)CH₂(OH), is a commonly used automobile antifreeze due to its water solubility and low volatility. Determine the freezing point of a solution made by dissolving 651 g of ethylene glycol in 2505 g of water. Given that the molar mass of ethylene glycol is 62.01 g/mol, the freezing point of pure water is 0°C, and the cryoscopic constant (Kf) for water is 1.86°C/m.
-6.79 oC
-7.79 oC
-8.79 oC
-9.79 oC
-7.79 oC
A solution made by dissolving 0.3 g of an unknown nonvolatile solute in 30 g of CCl₄ shows a boiling point that is 0.392°C higher than the boiling point of pure CCl₄. The ebullioscopic constant (Kb) for CCl₄ is 5.03°C·kg/mol. What is the molar mass of the solute?
328 g/mol
238 g/mol
128 g/mol
428 g/mol
128 g/mol
