Acids, Alkalis and Solubility (PAPER ONE)

Neutral - 7 Acids - Less than 7 Alkalis - More than 7

An indicator made from a mixture of different indicators and produces a range of colours based on the pH

Acid - red Alkaline - yellow

Acid - red Alkaline - blue

Acid - colourless Alkaline - pink

An atom that has become charged by losing/gaining electrons (CHARGED PARTICLE)

When acids are dissolved in water, they produce an excess of hydrogen ions (H+) e.g. hydrochloric acid is formed when hydrogen chloride dissolves in water and splits into H+ and Cl- ions

Alkalis produce an excess of OH- ions when in water e.g. sodium hydroxide splits into Na+ and OH- ions when it dissolves

As more hydrogen ions (H+) are added to the same volume, the concentration increases. The higher the concentration of H+ ions, the more acidic the solution becomes, which makes the pH lower The higher the concentration of hydroxide ions (OH-) in a solution, the more alkaline it becomes, which increases the pH

Water is a pure substance with a pH of 7 So, it contains low and equal concentrations of OH- and H+ ions

Concentration (g dmcubed) = amount dissolved/volume of solution

cmcubed —-> dmcubed = divide cmcubed by 1000

A concentrated solution is a solution that contains a lot of dissolved solute per unit volume

If the concentration of hydrogen ions is increased by a factor of 10, the pH decreases by 1. If the concentration decreases by a factor of 10, the pH increases by 1 e.g. a solution with a pH of 5 would have a concentration of H+ ions 10 x 10 = 100 times greater than a solution of pH 7

pH 4

Strong acids - Their molecules completely dissociate (break up) into ions when they dissolve in water, they produce a high concentration of H+ ions. They tend to have low pHs (0-2) weak acids - Their molecules do not dissociate completely into ions in solution produce a low concentration of H+ ions, ionisation of weak acids are reversible reactions, pHs 2-6

Any substance that reacts with an acid to form a salt and water only - all metal oxides are bases

During neutralisations, the hydrogen ions in the acid combine with oxide ions to form water. This removes the hydrogen ions, therefore increasing the pH which makes the solution become more neutral and less acidic

magnesium oxide + sulfuric acid —> magnesium sulfate + water

1) Measure 20cmcubed of dilute sulfuric acid using measuring cylinder and pour it into a conical flask 2) Warm the acid in a 50’c water bath 3) Add copper oxide powder to acid and stir 4) If all the copper oxide reacts, so disappears, add some more and stop when the copper oxide is in excess and no longer reacts 5) Filter the mixture and transfer the filtrate into evaporating basin 6) Heat evaporating basin by placing it over a beaker of water heated by a Bunsen burner and stop heating when crystals start to form 7) Pour solution into a watch glass and leave for a few days to allow all the water to evaporate

To ensure that all the acid is used up

Bases that can be dissolved in water are called alkalis

Not all bases are soluble, only soluble bases are alkalis

Group 1 hydroxides - e.g. sodium hydroxide Group 2 hydroxides - e.g. calcium hydroxide