2. Acids, bases, titrations, salts

Which property is NOT a characteristic of a base?

A: It reacts with carbonate to form carbon dioxide
B: It reacts with an acid to form a salt
C: It reacts with an ammonium salt to form ammonia
D: It turns universal indicator paper blue

A, as this is the property of an acid

B, as sodium hydrogen carbonate is mildly alkaline and vinegar is mildly acidic

A, as the solution R does not react with either, so is neutral

B, ammonia only produced from ammonium carbonate when it reacts with a base

C, it is not copper as copper is unreactive and less reaction than hydrogen

Dilute H2SO4 does not react with copper, leaving a pink/brown solid. Soluble ZnSO4, colourless solution forms

Acids ONLY react with metals above hydrogen

What is the colour of BaSO4?

It is a white precipitate

How could a student obtain pure dry crystals of sodium chloride from a solution of sodium chloride? [4]

• Heat the solution to evaporate some of the water and produce a saturated solution

• Leave to cool and crystallise

• Decant off the excess solution

• Pat the crystals dry

What colour flame is observed when sulfur combusts?

Blue