Acids and Bases

pH scale:

  • Ranges from 0 to 14, with 7 being neutral.

  • Values below 7 indicate acidic solutions, while values above 7 indicate basic solutions.

The further the pH value is from 7, the stronger the acid or base, respectively, with 0 being the strongest acid and 14 being the strongest base. This can be used to indicate the strength of an alkali or acid but only if the acids are at the same concentration.

universal indctr is a mix of different indicators and gives a colour depending on pH

pH range:

  • 0 - 3, strong acid - Hydrochloric acid

  • 4 - 6, weak acid - Ethanoic acid

  • 7, neutral - Water

  • 8 - 10, weak alkali - Ammonia solution

  • 11 - 14, strong alkali - Sodium hydroxide

Different indicators have different colours depending on whether the solution is acidic, alkaline or neutral but they do not show the pH

INDICATOR

ACID

NEUTRAL

ALKALI

litmus solution

red

purple

blue

phenolphthalein

colourless

colourless

pink

methyl orange

red

yellow

yellow

red litmus

stays red

stays red

turns blue

blue litmus

turns red

stays blue

stays blue

METAL HYRDOXIDE + ACID ——— SALT + WATER

NaOH + HCl ——— NaCl + H2O

METAL OXIDE + ACID ——— SALT + WATER

MgO + 2HCl ——— MgCl + H2O

METAL CARBONATE ——— SALT + WATER + CARBON DIOXIDE

AMMONIA + ACID ——— AMMONIUM SALT

TITRATION