Imagine two solutions with the same concentration and the same boiling point, but one has ethanol as the solvent and the other has carbon tetrachloride as the solvent. Determine that molal concentration, m (or b), and boiling point, Tb. Given

Ethanol

normal Boiling point: 78.4

Kb: 1.22

CCL4

normal boiling point: 76.8

Kb: 5.03

m = 0.42; Tb = 79°

Explanation: The relationship between boiling point of the solvent above a solution is directly proportional to the molal concentration of the solute, i.e.:

ΔT =

where

ΔT is the change in boiling point of the solvent;

is the molal boiling point elevation constant;

m is the molal concentration of the solute in the solution;

For there two solutions:

1) Ethanol:

ΔT =

Tb -

Tb - 78.4 = 1.22.m (1)

2) Carbon Tetrachloride:

Tb -

Tb - 76.8 = 5.03.m (2)

Solving the system of equations:

Tb - 78.4 = 1.22.m

Tb = 1.22.m + 78.4 (3)

Substituing (3) in (2)

1.22.m + 78.4 - 76.8 = 5.03m

3.81m = 1.6

m = 0.42

With m, find Tb:

T - 76.8 = 5.03.0.42

T = 2.11 + 76.8

T = 79°

Molal concentration is 0.42 and boiling point is 79°

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.