✔ 最佳答案
1.
A standard solution is a solution with known concentration. There are two types of standard solutions:
• A primary standard solution (or primary standard) is a standard solution that is prepared by dissolving a known mass of solute to form a known volume of solution. In other words, the concentration of a primary standard solution is found without using another standard solution.
• A secondary standard solution (or primary standard) is a standard solution that its concentration is found by titration. In other words, the concentration of a secondary standard solution is found by using another standard solution.
2.
Electron affinity of an element X is the enthalpy change when 1 mole of the gaseous X atoms gain 1 mole of electrons to form one mole of X- ions under standard conditions.
X(g) + e- → X-(g) --DH = electron affinity of X (in J/mol)
F has a less negative electron affinity than Cl unexpectedly.
Reason: F atom is very small. The attractions between incoming electrons and the original electrons are thus very greater. This causes less energy to release.
Electronegativity of an element is the ability to attract the bonding electron pair in chemical bonds.
F has a greater electronegativity than Cl.
Reason: F atom much small in size than Cl. Thus, the distance between the nucleus of F and the bonding electron pair is shorter than that of Cl. Thus, the bonding electron pair experiences an strong attraction by nucleus of F atom than by the nucleus of Cl atom.
Reduction potential is the tendency of reduction (gaining electrons).
F2(g) + 2e- → 2F-(aq) -- Higher reduction potential
Cl2(g) + 2e- → 2Cl-(aq) -- Lower reduction potential
Reasons:
• The F-F bond is weaker than the Cl-Cl bond, because of the strong repulsions between the non-bonding electron pairs of the small F atoms.
• The hydration of F- is more exothermic than Cl-, because of F- ions are much smaller in size and thus the polar water molecules are more strongly attracted by the F- ions.
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