C4: Chemical changes
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What colour are acids on the pH scale?
Red.
What colour are alkalis on the pH scale?
Blue/purple.
What does pH mean?
Power of hydrogen- a measure of the concentration of H+ ions in the solution.
What are 4 measuring instruments for pH?
Litmus paper, phenolphthalein, universal indicator and a pH probe (goes in the solution) attached to a pH meter.
What colour does blue litmus paper turn in acids?
Red.
What colour does blue litmus paper turn in alkalis?
Stays blue.
What colour does red litmus paper turn in acids?
Stays red.
What colour does red litmus paper turn in alkalis?
Turns blue.
What is useful about universal indicator?
It matches a shade on the pH scale.
What is the benefit of measuring pH digitally?
It is more accurate and gives numerical values rather than a colour, which is harder to interpret.
What is the equation for neutralisation?
Acid + base = salt + water.
How can neutralisation be shown in terms of hydrogen and hydroxide ions?
H+(aq) + OH-(aq) ⇒ H20(l)
What is the formula of sulfuric acid?
H2SO4
What is the formula of nitric acid?
HNO3
What is the formula of hydrochloric acid?
HCl
What is the formula of copper hydroxide?
Cu(OH)2
What is the formula of sodium hydroxide?
NaOH
What is the formula of magnesium oxide?
MgO
What makes a substance acidic?
H+ ions.
What salt does sulfuric acid produce in neutralisation reactions?
Sulphate
What salt does hydrochloric acid produce in neutralisation reactions?
Chloride
What salt does nitric acid produce in neutralisation reactions?
Nitrate
What do acids donate in neutralisation reactions?
H+ ions.
Why are strong acids more reactive than weak acids of the same concentration? What does this mean?
They dissociate more H+ ions so the rate of reaction is quicker.