[16] Acids, alkalis, titrations and salt preparations

How does red litmus paper distinguish between acidic and alkaline solutions?

How does blue litmus paper distinguish between acidic and alkaline solutions?

How does purple litmus paper distinguish between acidic and alkaline solutions?

acidic - red
neutral - red
alkaline - blue

acidic - blue
neutral - blue
alkaline - red

acidic - red
neutral - purple
alkaline - blue

How does phenolphthalein indicate acidity or alkalinity?

Acidic solution: Colorless
Neutral solution: Colorless
Alkaline solution: Pink

How does methyl orange indicate acidity or alkalinity?

Acidic solution: Red
Neutral solution: Orange
Alkaline solution: Yellow

How is a universal indicator used to measure the pH of a solution?

The universal indicator changes color based on the pH and can be matched to a pH scale to determine the approximate value.

What ions do acids produce in aqueous solution?

Acids produce hydrogen ions (H⁺) in aqueous solution.

What ions do alkalis produce in aqueous solution?

Alkalis produce hydroxide ions (OH⁻) in aqueous solution.

What happens when an acid reacts with an alkali?

Neutralization occurs, forming a salt and water.

How do you make NaCl

titration (acid + alkali)
use a pipette to measure a known amount of alkali into conical flask, add phenolphthalein indicator
rinse burette with acid
take initial reading on burette
place conical flask under burette, add acid while swirling until solution in conical flask turns colourless
write down final reading of burette
repeat titration without indicator
heat solution until saturated
cool
crystallize
filter
dry with paper towel

method to make CuSO₄

acid + metal oxide
gently warm H2SO4 to 60 C
add CuO and stir
add CuO until excess
filter to remove excess metal oxide
heat gently until solution becomes saturated
leave to cool
crystallise
filter off remaining liquid
wash with distilled water
dab crystals dry

why do we heat up the acid

to speed up the reaction

why do we add metal oxide in excess

so all of the acid reacts

how do we know the solution is saturated

crystals form round the edge

method to make silver iodide

precipitation
mix AgNO3 and KI
filter
wash with distilled water
dry

what is the balanced chemical equation of making copper sulphate

CuO + H₂SO₄ → CuSO₄ + H₂O

What is the reactivity order of common metals? from most to least

Potassium, Sodium, Lithium, Calcium, Magnesium, Aluminium, Zinc, Iron, Copper, Silver, Gold

metal + acid →

salt + hydrogen

metal oxide + acid →

salt + water

metal hydroxide + acid

salt + water

metal carbonate + acid ->

salt + water + carbon dioxide