This is a double replacement reaction in which the cations and anions switch places, forming new products. The general form of this reaction is AB + CD ##rarr## AD + CB. In order for a double replacement reaction to occur, the reactants must be soluble in water, and one of the products must be a gas, water, or a solid precipitate.
In this double replacement reaction, the precipitate barium sulfate, ##”BaSO”_4(“s”)## will form. If no gas, water, or precipitate forms, then there is no reaction and you would write N.R. for no reaction after the arrow.
The balanced molecular equation for this reaction is:
##”Ba(NO”_3)_2(“aq”)”## + ##”H”_2″SO”_4(“aq”)## ##rarr## ##”BaSO”_4(“s”)## + ##”2HNO”_3(“aq”)##
We can know that barium sulfate is a solid precipitate by consulting a solubility table like the one below:
You can see that barium sulfate is listed as “s”, which means that it does not dissolve in water, so it precipitates out of solution, forming a solid.
The complete ionic equation , which shows all of the ions and the precipitate is:
##”Ba”^(2+)(“aq”)## + ##”2NO3″^(-)(“aq”)## + ##”2H”^(+)(“aq”)## + ##”SO”_4^(2-)(“aq”)## ##rarr##
##”BaSO”_4(“s”)## + ##”2H”^(+)(“aq”)## + ##”2NO3″^(-)(“aq”)##
The net ionic equation , which shows only those ions involved in the formation of the precipitate, and the precipitate is:
##”Ba”^(2+)(“aq”)## + ##”SO”_4^(2-)(“aq”)## ##rarr## ##”BaSO”_4(“s”)##
The formula for barium sulfate could also be written as ##”BaSO”_4####darr##, which indicates that it is a precipitate.
