is Na2O an alkali or not? cos an an alkali is a soluble base so is NaOH an alkali along with Na2O im veey confused with it. pls help me clarify what is what
Originally posted by SgStudentStressed:is Na2O an alkali or not? cos an an alkali is a soluble base so is NaOH an alkali along with Na2O im veey confused with it. pls help me clarify what is what
An alkali ( noun ) is any solution ( adjective : "alkaline solution" ) which contains a higher concentration of OH- ions over H+ ions.
Bases which are able to undergo hydrolysis ( hydrolysis = "chemical reaction with water" ) to generate soluble products are called "soluble bases" because the solid base appears to dissolve in water (it is really undergoing a chemical reaction with water, ie. hydrolysis, to generate soluble products).
For instance, Na2O or sodium oxide, contains the strongly basic O2- dinegative oxide ion, which in a bid to stabilize itself, abstracts protons H+ ions from water, generating 2OH- ions.
O2- + H2O ---> 2OH-
Since NaOH is soluble (unlike say, MgO), the resulting solution is alkaline, ie. has a higher concentration of OH- ions over H+ ions, and has pH greater than 7 (note that pH = 7 holds true for neutral solutions (only) at 25 deg C; therefore at 25 deg C, any pH greater than 7 is considered alkaline).
There are 3 different definitions of acids (and therefore, of bases). These are : Bronsted-Lowry, Lewis and Arrhenius. For 'O' levels, the Arrhenius definition "an acid dissolves in water to generate H+ ions" is often used, even though the other two definitions (Bronsted-Lowry and Lewis), used at 'A' levels, are more correct and useful.
To summarize :
A (Bronsted-Lowry) base is any species that accepts protons H+ ions. A 'soluble' base undergoes hydrolysis ('chemical reaction with water') to generate a solution containing a higher concentration of hydroxide OH- ions over protons H+ ions, which is called an "alkali" or "alkali solution" or "alkaline solution".
so.. is Na2O a base n is NaOH an alkali or smthing else at my current level?
Originally posted by SgStudentStressed:so.. is Na2O a base n is NaOH an alkali or smthing else at my current level?
Na2O(s) is a base that when dissolved in water will produce the alkali NaOH(aq).
summary
An alkaline is a soluble base
Originally posted by SBS n SMRT:summary
An alkaline is a soluble base
To be precise, an alkali is the aqueous version of a soluble base. A base can exist in any state, but an alkali by definition must be aqueous.
I disagree with the point that an alkali is the aquesous version of a soluble base. A base in its molten state which produces OH- ions is also an alkali even if the base is insoluble in water.
Anyway, we don't say Na2O or NaOH in solid state are alkali. NaOH in aqueous state is while Na2O does not have an aqueouse state as it reacts with water.