C5 - Chemical Change Flashcards
List the order of the reactivity series including carbon.
Potassium , sodium , lithium , calcium , magnesium , aluminium , carbon , zinc , iron , tin , lead , hydrogen , copper , silver , gold , platinum .
What is oxidisation in terms of oxygen?
The gain of oxygen.
What is reduction in terms of oxygen?
The loss of oxygen
What is the definition of a displacement reaction?
A chemical reaction where a more reactive metal displaces a less reactive metal.
Why does a displacement reaction occur?
A displacement reaction occurs because a more reactive metal pushes out(displaces) a less reactive metal from it’s compound.
What does oxidisation mean in terms of electrons?
The loss of electrons.
What does reduction mean in terms of electrons?
The gain of electrons.
Describe displacement reactions using an ionic equation between calcium and copper sulfate
Ca^2+ + CuSO_4 —–> CaSO_4 + Cu^2+
Explain how carbon is used to reduce an ore.
The carbon displaces the metal from the compound, and removes the oxygen from the oxide, this leaves the metal by itself.
Explain how hydrogen is used to reduce an ore.
The ore is heated with hydrogen, the hydrogen displaces the less reactive metal from its compound and leaves the metal on its own.
Describe how metals can be extracted.
Metals are extracted from their ore by using displacement reactions with carbon and hydrogen (and electrolysis).
Explain why some metals are found uncombined in the Earth’s crust.
Some metals are found uncombined (in a compound) in the earth’s crust because the metal is very unreactive or inert.
What is the definition of a salt?
A compound formed when some or all of the hydrogen in an acid is replaced by a metal.
Describe how to make a salt.
By reacting a metal with an acid.
Explain ionically the reaction between a metal and an acid.
For a metal to react with an acid it must be more reactive than hydrogen; if this condition is met the metal will displace the hydrogen and form an ionic compound with the non metal part of the acid.
Describe a method to prepare a pure, dry sample of a soluble salt from an insoluble substance and a dilute acid.
- Place base into acid.
- Speed up reaction via heat and shaking.
- Wait for reaction to end.
- Filter out any excess base.
- Leave to evaporate in an evaporating basin at room temperature to get best quality crystals.
Why is a reaction between a base and a dilute acid a neutralisation reaction?
This is because a base is alkali and the acid is acidic. So these two substances practically ‘cancel’ each other out.
Explain how alkalis are a subgroup of bases.
Because alkalis are soluble bases.
What is the general equation for metal carbonate + acid?
Metal carbonate + acid –> salt + water + carbon dioxide
What is the method for making salt from metal carbonate + acid?
- Place metal carbonate in acid
- Place either pH meter or universal indicator in solution.
- Wait for pH to be 7.
- Filter out left over carbonate.
- Leave to evaporate in an evaporating basin at room temperature for crystals to form.
Why is the reaction between ammonium and dilute acids important in agricultural?
Because the ammonium forms salts from the non hydrogen ions in the acid and becomes a useful nutrient for plants to grow.
How do we tell between acids and alkalis with universal indicator?
Acids turn Ul yellow-red and alkalis turn Ul blue-purple.
How can we use universal indicator to determine approximate pH?
We can use a spectrum of colours with approximate pH values assigned to them and compare them to our solution.
Describe the pH scale.
A scale used to measure the concentration of H+ ions in a solution and thus how acidic or alkali it is.
