D
Molecular motion increases as temperature increases and therefore increasing the molecular motion increases collision frequency.
Explanation:
When a substance is heated, its molecules gain increased kinetic energy even as the substance increases in temperatures. With higher kinetic energy, this means the molecules are moving more rapidly and hence collision between the molecules will be more frequent and of higher energy. It is these high energy collisions that cause the molecules to move further away from each other with increased temperatures (why substances expand).
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Answer:
B. II.
Explanation:
The idea of recrystallization works when the solubility of the target substance decreases as the temperature of the solution decreases.
The method of recrystallization involves dissolving the solute in a suitable hot solvent and then allow the solution to cool gradually. The pure solute dissolves in the hot solvent and then separates out of the solution as it is cooled to room temperature.
Hence recrystallization is preferred over solvent extraction when the desired compound is poorly soluble in the solvent pair at low temperatures and greatly soluble in the solvent pair at high temperatures.
Answer:
When the electron changes levels, it decreases energy and the atom emits photons. The photon is emitted with the electron moving from a higher energy level to a lower energy level. The energy of the photon is the exact energy that is lost by the electron moving to its lower energy level.
Explanation:
Ca= 2 ve
Be=2 ve
Mg=2 ve because they are in Group 2a.
They are slightly less reactive than Group 1a, but more dense that Group 1a.
