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A 100 cm³ measuring cylinder is the most efficient option for adding 100 cm³ of water to 50 beakers because it allows the scientist to measure the entire 100 cm³ volume of water in one go.
Using a 50 cm³ burette (option A) would require the scientist to measure and pour half the volume of water into each beaker twice, which would be slower and less precise compared to using a larger measuring cylinder.
Similarly, using a 25 cm³ graduated pipette (option C) four times for each beaker would be even slower, as the scientist would need to measure and pour a smaller volume of water multiple times.
Using a 100 cm³ gas syringe (option B) would be similar to using a measuring cylinder, but a measuring cylinder is generally easier to use and less prone to errors compared to a gas syringe, especially when making multiple measurements.
Therefore, using a 100 cm³ measuring cylinder is the quickest and most efficient method to add 100 cm³ of water to 50 beakers.
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Fractional distillation is a method used to separate and collect mixtures based on their boiling points.
A) Copper (II) sulfate and water - chromatography: Chromatography is a method used to separate components based on their physical and chemical properties, but it is not the best method to separate copper (II) sulfate and water. These two substances can be separated by simple filtration.
B) Methanol and ethanol - evaporation: Evaporation is a method used to separate mixtures based on the boiling points of their components. However, methanol and ethanol have very similar boiling points, making it difficult to separate them through evaporation alone. Other methods, such as distillation may be required.
D) Sand and barium sulfate - filtration: Filtration is a method used to separate solid particles from a liquid. In this case, sand and barium sulfate cannot be separated by filtration. Barium sulfate is an insoluble salt, so both Barium Sulfate and sand will not dissolve in water and remain as residue.
Therefore, the only option that is correct is C) oxygen and nitrogen - fractional distillation. This method uses differences in boiling points to separate the components of a mixture.
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The observations indicate that the cation present in the colorless solution forms a white precipitate with both sodium hydroxide and ammonia, and this precipitate dissolves in excess of both reagents. This suggests that the cation is a metal hydroxide that is soluble in excess base.
Among the options given, only Zn2+ fits these observations. Zinc hydroxide is insoluble in water but dissolves in excess sodium hydroxide or ammonia to form a colorless, complex ion. Thus, the correct answer is D: The cation present is Zn2+.
On the other hand, the presence or absence of chloride anions cannot be deduced from the given observations as many other metal cations form white precipitates with chloride ions.
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The correct answer is A: particles become more ordered; particles gain energy.
During the process of freezing, a substance transitions from the liquid phase to the solid phase, and the particles in the substance undergo a change in their arrangement. As the temperature of the substance decreases, the average kinetic energy of the particles decreases, and the particles start to move more slowly. As the temperature approaches the freezing point of the substance, the particles begin to arrange themselves in a more ordered manner, with the particles moving less freely and taking on a more rigid, crystalline structure.
The particles gain energy during the process of freezing because during freezing more intermolecular bonds are formed. Formation of any bond is and endothermic process. Overall, endothermic processes take in energy.
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