2(g) Acids, bases, and protons

what salts are always soluble?

sodium, potassium, and ammonium (SPA salts)

nitrates

what are the solubility rules for chlorides?

most are soluble

silver and lead (II) chloride are insoluble (Ag, Pb)

what are the solubility rules for sulfates?

most are soluble

barium, calcium, and lead (II) sulfate are insoluble (Ba, Ca, Pb)

what are the solubility rules for carbonates?

all are insoluble except for the SPA salts

what are the solubility rules for hydroxides?

all are insoluble except for the SPA salts

calcium hydroxide is slightly soluble in water

define acids and bases

acids are proton donors, as they ionize in solution, producing protons (H⁺ ions)

bases are proton acceptors, as they ionize in solution, producing OH^- ions, which can accept protons

what are some examples of bases? (remember the bonus one)

metal oxides

metal hydroxides

metal carbonates

ammonia solution

what are the products when an acid reacts with a metal?

acid + metal → salt + hydrogen

what are the products when an acid reacts with a metal oxide?

acid + metal oxide → salt + water

what are the products when an acid reacts with a metal hydroxide?

acid + metal hydroxide → salt + water

what are the products when an acid reacts with a metal carbonate?

acid + metal carbonate → salt + water + carbon dioxide

if there is effervescence present in an acid-base reaction, what must the base be?

a metal carbonate

the bubbles are CO₂

what is the difference between a base and an alkali?

an alkali is a base that is soluble in water

all alkalis are bases, but not all bases are alkalis

what is the difference between ammonia and ammonium, and what are their formulas?

what is special about ammonia?

ammonia is the gas - NH₃

ammonium is the ion - NH₄⁺

ammonia solution is also a base - when ammonia reacts with water, it produces hydroxide ions

NH₃ + H₂O → NH₄⁺ + OH^-

TIP: aqueous ammonia and ammonium hydroxide are the same thing

what method should you use for making an insoluble salt, and how?

precipitation method

1. mix together equal volumes of two aqueous solutions, one containing the postive ion, and one containing the negative ion

2. filter out the precipitate with filter paper and a funnel

3. wash the precipitate with distilled water to remove traces of other solutions

4. leave to dry in a warm place

what method should you use for making a soluble salt that is not a SPA salt, and how?

acid + insoluble base method

1. put 50cm³ of dilute acid into a beaker and heat on a tripod with gauze using a bunsen burner

2. add insoluble base while stirring until no more dissolves (to ensure that all the acid reacts)

3. transfer the solution into an evaporating basin and heat until you are left with a saturated solution (check that it is saturated by dipping in a glass rod - if it is saturated, crystals will form)

4. leave the solution to cool and crystals to form

5. rinse the crystals with some distilled water and leave them to dry in a warm place