How do you predict the products in acid-base reactions?

1 Answer
Ernest Z. · Media Owl · dwayne
Feb 19, 2014

You predict the products of acid-base reactions by pairing each cation with the anion of the other compound.

Explanation:

Acid-base neutralization is a special case of double displacement reaction.

We can use the same techniques to predict the products.

In acids, the cation is always H+.

Let's use the neutralization of stomach acid (HCl) by milk of magnesia [Mg(OH)2] as an example.

HCl + Mg(OH)2→?

(a.) Divide the acid into H+ ions and negative ions.

HCl→H++Cl-

(b.) Divide the base into positive ions and OH- ions.

Mg(OH)2→Mg2+OH-

(c.) For products, combine the H+ and OH- ions to make H2O.

Then combine the positive and negative ions to make a salt.

Remember to balance the positive and negative charges in the salt.

In this case, Mg2+ and Cl- make MgCl2.

(H++Cl-)+(Mg2++OH-)→(Mg2++Cl-)+(H++OH-)

HCl + Mg(OH)2→MgCl2+H2O

(d.) Balance the equation.

2HCl+Mg(OH)2→MgCl2+2H2O

EXAMPLE

Complete and balance an equation for the reaction between HBr and Al(OH)3.

Solution

HBr+Al(OH)3→?

(H++Br-)+(Al3++OH-)→(Al3++Br-)+(H++OH-)

HBr + Al(OH)3→AlBr3+H2O

3HBr + Al(OH)3→AlBr3+3H2O

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