Topic 4: Chemical Changes Flashcards
What is the difference between the strength of an acid and the concentration of an acid?
Strength of an acid - how much acid dissociates
Concentration- how much acid there is in a certain volume
Acid + metal oxide -> ?????
Salt + water
Acid + metal hydroxide -> ??????
Salt + water
Acid + metal carbonate -> ??????
Salt + carbon dioxide + water
Are metal oxides and hydroxides acids or alkalis?
Alkalis
What is an acid?
A substance that forms aqueous solutions with a pH of less than 7.
They form H+ ions in water
What is a base?
A substance with a oH greater than 7
What is an alkali?
A base that dissolves in water to form a solution with a pH greater than 7
Form OH- ions in water
Neutralisation equation
H+ + OH- -> H2O
What are strong acids?
Acids which ionise completely in water.
All acid particles dissociate to release H+ ions
What is a weak acid?
Acids that do not fully ionise in solution
Only a small proportion of acid particles dissociate to release H+ ions
What type of reaction is the ionisation of a weak acid?
A reversible reaction
What is pH a measure of?
The concentration of H+ ions in the solution
If a strong and weak acid have the same concentration, which will have a higher pH?
The weaker acid
How does potassium react with water?
Fizz + melts + burns
How does sodium react with water?
Fizz + melts
How does lithium react with water?
Fizz
How does calcium react with water
Fizz
How does magnesium react with water?
Slowly produces gas over hours/days
How does zinc react with water?
Slowly oxidises
How does iron react with water?
Rusts
How does copper react with water?
It doesn’t
How do potassium, sodium, lithium, calcium, magnesium react with oxygen?
Burn to produce white oxides
What is the difference between combustion and burning?
combustion is heating and no flames are produced
in burning most of the energy is converted to light energy and this results in less heat energy as compared to combustion.
How do zinc, iron, copper react with oxygen?
Combust to produce oxides
How do potassium, sodium, lithium react with acid?
N/A - too dangerous
How do calcium, magnesium,zinc , iron react with acids?
They fizz and disappear
How does copper react with acids?
No reaction unless a concentrated acid