Acids, Alkalis & salts (46-47, 50) (paper 1) Flashcards
define acid
produces H+ in water ~ proton donors
what pH scale do acids have
less than 7
define a base
substance which can neutrilise an acid ~ proton acceptors
define an alkali
soluble producing OH- ions in waterr
what pH scale do alkalis have
greater than 7
what colour are strong acids in universal indicator
red
what colour are weak acids in universal indicator
orange / yellow
what colour is water in universal indicator
green
what colour are strong alkalis in universal indicator
purple
what colour are weak alkalis in universal indicator
blue
what is a digital way of understanding the pH of a substance
a pH meter
name the three most common acids and their molecular formula
- Hydrochloric acid (HCl)
- Sulfuric acid (H2SO4)
- Nitric acid (HNO3)
what type of salt would be formed from hydrochloric acid
metal chloride
what type of salt would be formed from sulfuric acid
metal sulfate
what type of salt would be formed from nitric acid
metal nitrate
what is produced when a metal reacts with an acid
- salt
- hydrogen
what is produced when a metal oxide reacts with an acid
- salt
- water
what is produced when a metal hydroxide reacts with an acid
- salt
- water
what is produced when a metal carbonate reacts with an acid
- salt
- caron dioxide
- water
what is the difference between an alkali and a base
bases are insoluble, alkalis can be dissolved in water
what is an indicator
something which changes colour depending on the pH of a solution
name the indicators
- universal indicator
- litmus paper
- phenolphthalein
- methyl orange
what is the colour change for litmus paper
- acid = red
- alkali = blue
what is the colour change for phenolphthalein
- acid = colourless
- alkali = pink
what is the colour change for methyl orange
- acid = red
- alkali = yellow
what is the reaction between an acid and alkali called
a neutralisation
show the chemical equation for a neutralisation reaction in the terms of H+ and OH-
H+ (aq) + OH- (aq) -> H2O (l)
what is produced when ammonia reacts with an acid
ammonium salt
what practicle should you do when making a soluble salt from an acid and insoluble base
the excess solid method
describe the excess solid method
- heat the sulfuric acid
- add black copper oxide powder to excess and stir
- filter out excess copper oxide
- heat copper sulphate (blue) solution until crystalisation point and leave to cool
- filter out crystals and wash with distilled water
- leave to dry between filter paper
why do we add copper ooxide powder to excess in the excess solid method
to ensure all the sulfuric acid has reacted
