Question

traces of water can be removed from ethanol distillate by a. vacuum distillation b. evaporation c. fractional distillation d. decantation
the enthalpy change when one - mole of an ionic compound is formed from its constituent ions in the gaseous state is called a. lattice energy b. activation energy c. bond energy d. hydration energy
the number of isomers that could be formed by c₅h₁₂ is a. 5 b. 3 c. 4 d. 2
during electrolysis, the type of electrode used affects the a. quantity of products b. selective discharge of ions c. rate of electrolysis d. formation of hydrogen ions
an increase in temperature of a gas causes an increase in its pressure because there is an increase in the a. average velocity of the molecules b. mean free path of the molecules c. number of collisions between the molecules d. density of the molecules

Explanation:

1. Traces of water can be removed from ethanol distillate by fractional distillation as ethanol and water form an azeotropic mixture and fractional distillation is effective for separating components with close - boiling points.
2. The enthalpy change when one mole of an ionic compound is formed from its constituent ions in the gaseous state is called lattice energy.
3. For $C_4H_{10}$, the number of isomers is 2 (n - butane and isobutane).
4. During electrolysis, the type of electrode used affects the selective discharge of ions. Different electrodes have different reactivity and can influence which ions are preferentially discharged at the electrode surface.
5. An increase in the temperature of a gas causes an increase in its pressure because there is an increase in the average velocity of the molecules. According to the kinetic - molecular theory, higher temperature means higher average kinetic energy and thus higher average velocity of gas molecules, leading to more frequent and forceful collisions with the container walls and increased pressure.

Answer:

1. C. fractional distillation
2. A. lattice energy
3. D. 2
4. B. selective discharge of ions
5. A. average velocity of the molecules