Acids and Bases

What is an acid

A substance that dissociates in water to form H+ (hydrogen ions). It is a proton donor

What is a base

A substance that dissociates in water to form OH- (hydroxide ions). It is a proton acceptor

Net Ionic Equation

H+ + OH- →H2O

Limitations to Arrhenius Theory

Applicable only to acids with formula HX: Eg. HCl, HBr. Does not work as NH3

Applicable to only bases with formula YOH: Eg. NaOH, KOH

pH

Potential of hydrogen. So pH = -log(H+)

Where the H+ is the mols of H+ ions in the reaction.

So pH of 0.02 mols of H₂SO_4.

The reaction is H₂SO₄ → 2H⁺ + SO₄^2- , so there are 2 mols of H⁺ ions , so it’s pH = 2(-log(0.02)) = 1.40. Makes sense since it is an acid.

Metal + Acid reactions

Metal + Acid → Metal salt + H₂ gas

(don’t forget the charges on the positive metal and negative non metal)

Eg. Mg + 2HCl → H₂ + MgCl₂

Metal oxide + Acid reactions

Metal oxide (O) + acid → Water + salt

(don’t forget the charges on the positive metal and negative non metal)

CuO + 2HCl → H₂O + CuCl₂

Metal hydroxide + acid reactions

Metal hydroxide (OH) + acid → Water + salt

(don’t forget the charges on the positive metal and negative non metal)

Eg. NaOH + HNO₃ → H₂O + NaNO₃

Metal carbonate + Acid reactions

Metal carbonate (MCO₃)+ acid → Salt + H₂O + CO₂ (gas)

(don’t forget the charges on the positive metal and negative non metal)

Eg. MgCO₃ + 2HCl → MgCl₂ + H₂O + CO₂

Metal hydrogencarbonate + Acid reactions

Metal hydrogencarbonate (HCO₃) + acid → CO₂ + H₂O + Salt

Eg. NaHCO₃ + HCl → H₂O + CO₂ + NaCl

What is a titrate

The solution with a known concentration. You add this from the burette (it is usually a base for normal titrations and turns the base in the conical flask pink)

What is the analyte

The solution with the unknown concentration that you're trying to determine. It's usually in the conical flask and it is usually an acid that turns pink

What is phenolphthalein

It is an indicator that is colorless in acid, and pink in a basic solution

pH scale

Titration description

A base (eg. NaOH) is in a burette. It is the titrate. You add phenolphthalein to the acid (eg. HCl). HCl is the analyte since it turns pink. Phenolphthalein is colorless in acidic solution and turns pink when in basic solution. Slowly add the titrate to the analyte and monitor the color change. When the analyte turns a VERY light pink, it has gone from acid to weak base. This shows it has been neutralized.

Strong acid curve in titration

Strong base curve in titration