Acids and Bases 2

● Equations that only show the chemical species that have participated in the reaction (such as ions and molecules). ● Ions that are chemically unchanged for the entire process are called spectator ions - they can be removed from the equation. ● Like typical chemical symbol equations, ionic equations must be balanced. The resulting (net) ionic equation should be as simple as possible.

● Reactions between reactive metals and acids are single replacement reactions. Mg (s) + 2 HCl (aq) → MgCl2 (aq) + H2 (g) ● The metal is more reactive than hydrogen so it displaces hydrogen from its compound.

solution AB + solution CD → precipitate AC + solution BD When two aqueous ionic solutions are mixed together, if an insoluble ionic compound is produced, a precipitate will be formed. During the process, the cations and the anions of the two solutions are exchanged.

It is a solution which remains above a precipitate

it settles and falls to the bottom of the solution

white precipitate of silver chloride is produced. Overall equation: AgNO3 (aq) + NaCl (aq) –> AgCl(s) + NaNO3 (aq) Ionic equation: Ag+ (aq) + Cl-(aq) –> AgCl(s)

Concentration refers to the amount (number of moles) of solute dissolved in a unit volume (dm3) of solution. Unit: mol dm^-3

Strength refers to the degree / extent of dissociation of the acid/ base when dissolved in water.

Hydrochloric acid HCl Sulphuric acid H2SO4 Nitric acid HNO3

Group 1 metal hydroxides - Sodium hydroxide NaOH - Potassium hydroxide KOH Barium Hydroxide - Ba(OH)2

They dissolve completely or fully in water

Ethanoic acid CH3COOH Carbonic acid H2CO3

Ammonia NH3

Concentration = number of moles found in 1 dm3 of solution. Strength = Degree of dissociation of acid in aqueous solution

Organic acids are acidic because they contain COOH group. They are weak acids. propanoic acid - monoprotic oxalic acid - diprotic citric acid - triprotic

● Carbonic acid is an aqueous solution of carbon dioxide. ● It is formed by bubbling CO2 (g) in water: CO2 (g) + H2O (l) ⇌ H2CO3 (aq) ● Dissociation: H2CO3 (aq) ⇌ H+ (aq) + HCO3-(aq) ● To write the equation for the dissociation of acids or bases in water, we use “→” for strong acids and bases, but we use “⇌” for weak acids and bases

• Extent of dissociation - the stronger the acid / base, the larger the extent of dissociation. ● Strong acid fully dissociates: HCl (aq) → H+ (aq) + Cl- (aq) ● Weak acid partially dissociates: CH3COOH (aq) ⇌ CH3COO- (aq) + H+ (aq) With the same concentration of acid/ base, the ion concentration of a strong acid/ base is higher. ● With the same concentration of acids, the H + ion concentration of a stronger acid is larger. ○ The pH of 1M HCl(aq) is lower than the pH of 1M CH3COOH(aq) ● With the same concentration of bases, the OH- ion concentration of a stronger base is larger. ○ The pH of 1M NaOH(aq) is higher than the pH of 1M NH3 (aq)

Vigor of reaction - under same concentration, the stronger the acid or base, the more vigorous the reaction and the faster the reaction rate. ● Reactions between stronger acids and metals / metal carbonates - rate of bubble production is higher ● Reaction between stronger acids and bases - more heat produced and greater temperature change

Electrical conductivity - it depends on the presence of mobile ions in the solutions. ● Stronger acids / bases have higher concentration of mobile ions in the solution, causing the electrical conductivity to be higher. ● This can be tested by connecting the solution in a complete circuit with a light bulb and observe its brightness, or measure the current using an ammeter.