Reactions in Aqueous Solution

Chapter 4 – Part 3

Acid Base Reactions

Proton Transfer Reactions AKA - Neutralization

Acids:

  Substances that increase the concentration of H + when dissolved in water (Arrhenius).

Proton donors (Brønsted–Lowry).

Acids

There are only seven strong acids:

Monoprotic

acids HCl H + + Cl HNO 3 H + + NO 3 CH 3 COOH H + + CH 3 COO Strong electrolyte, strong acid Strong electrolyte, strong acid Weak electrolyte, weak acid 4.3

Diprotic

acids H 2 SO 4 H + + HSO 4 HSO 4 H + + SO 4 2-

Triprotic

acids H 3 PO 4 H 2 PO 4 HPO 4 2 H + + H 2 PO 4 H + H + + HPO 4 2 + PO 4 3 Strong electrolyte, strong acid Weak electrolyte, weak acid Weak electrolyte, weak acid Weak electrolyte, weak acid Weak electrolyte, weak acid 4.3

Bases:

  Substances that increase the concentration of OH − when dissolved in water (Arrhenius).

Proton acceptors (Brønsted–Lowry).

Bases

The strong bases are the soluble salts of hydroxide ion:

Neutralization Reactions

Generally, when solutions of an acid and a base are combined, the products are a salt and water. HCl ( aq ) + NaOH ( aq )  NaCl ( aq ) + H 2 O ( l ) Salts are less reactive than acids and bases.

Why do they do that?

Neutralization Reactions

When a strong acid reacts with a strong base, the net ionic equation is… HCl ( aq ) + NaOH ( aq )  NaCl ( aq ) + H 2 O ( l )

Gas-Forming Reactions

 Sometimes the expected product predicted by just switching the ion partners decomposes to give a gaseous product (CO 2 or SO 2 ).

CaCO 3 ( s ) + HCl ( aq )  CaCl 2 ( aq ) NaHCO 3 ( aq ) + HBr ( aq )  NaBr ( aq + CO ) 2 + CO ( 2 g ( ) g ) + H 2 O ( l ) + H 2 O ( l ) SrSO 3 ( s ) + 2 HI ( aq )  SrI 2 ( aq ) + SO 2 ( g ) + H 2 O ( l ) Why do they do that?

Gas-Forming Reactions

  This reaction gives the predicted product, but you had better carry it out in the hood, or you will be very unpopular!

Just as in the previous examples, a gas is formed as a product of this reaction: Na 2 S ( aq ) + H 2 SO 4 ( aq )  Na 2 SO 4 ( aq ) + H 2 S ( g )

Solution Stoichiometry

Count with Volume!

Molarity

  Two solutions can contain the same compounds but be quite different because the proportions of those compounds are different.

Molarity is one way to measure the concentration of a solution.

Molarity (

M

) = moles of solute volume of solution in liters

4.5

Making Solutions

M

=

molarity

= moles of solute liters of solution What mass of KI is required to make 500. mL of a 2.80

M

KI solution?

4.5

Dilution

is the procedure for preparing a less concentrated solution from a more concentrated solution.

Dilution Add Solvent Moles of solute before dilution (i)

M

i V i = = Moles of solute after dilution (f)

M

f V f 4.5

How would you prepare 60.0 mL of 0.200

M

HNO 3 from a stock solution of 4.00

M

HNO 3 ?

4.5

Using Molarities in Stoichiometric Calculations

Titration

The analytical technique in which one can calculate the concentration of a solute in a solution.

What volume of a 1.420

M

NaOH solution is Required to titrate 25.00 mL of a 4.50

M

solution?

H 2 SO 4 4.7