The vapor pressure of benzene, c6h6, is 100.0 torr at 26.1 °c. assuming raoult's law is obeyed, how many moles of a nonvolatile solute must be added to 100.0 ml of benzene to decrease its vapor pressure by 10.0% at 26.1 °c? the density of benzene is 0.8765 g> cm3.

According to Raoult's law:

   -(1)

where is observed vapor pressure of the solution, is mole fraction of solvent, and is vapor pressure of the pure solvent.

Vapor pressure of benzene =   (given)

Reduction in vapor pressure on addition of non-volatile solute = 10.0 %   (given)

So, vapor pressure of the component in the solution =

Substituting the values in formula (1):

Mole of benzene =

Mole of benzene =

Since,

So,

Hence, moles of a nonvolatile solute to be added is .

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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.