C2 Salts And Electrolysis Flashcards
Give example of exothermic reactions.
Combustion, the burning of fuels is exothermic.
Neutralisation reactions(acid + alkali)
Oxidisation reactions. Adding sodium to water produced heat so it is exothermic.
Respiration.
Define exothermic reaction.
It is a reaction which transfers energy to the surroundings, usually in the form of heat and usually shown by a rise in temperature.
What are the uses of exothermic reactions?
Some hand warmers, use the oxidation if iron in air to produce heat.
Iron turns into hydrated iron oxide. The reaction is similar to rusting. Sodium chloride is used as a catalyst.
Self heating cans of coffee rely on them. Calcium oxide and water react to produce calcium hydroxide.
Define endothermic reaction.
An endothermic reaction is one which takes in energy from the surroundings, usually in the form of heat and is usually shown by a fall in temperature.
What are the uses of endothermic reactions?
They can be used in sports injury packs. They take in heat and pack becomes cold.
Give an example of an endothermic reaction.
Thermal decomposition reactions are endothermic.
Calcium carbonate thermally decomposes into CO2 and calcium oxide.
Give an example of a reversible reaction and its endothermic/ exothermic properties.
Hydrates copper sulphate thermal decomposes into anhydrous copper sulphate and water. These products produce heat when reacted together.
In a reversible reaction, the forwards energy is the same as the reverse energy.
What is a base?
A substance with a pH of greater than 7.
What is an alkali?
A soluble hydroxide It forms OH- ions in water.
What happens in a neutralisation reaction?
Acid + base = salt + water.
What are the state symbols?
S- solid l- liquid. g-gas. aq-dissolved in water
What happens when an acid reacts with a metal.
Acid + metal = salt + hydrogen.
What happens when copper is mixed with a dilute acid?
Nothing will happen. As copper is less reactive than hydrogen no hydration or salt will be produced.
What salts will hydrochloric acid produce when reacted with metal?
Chloride salts.
Hydrochloric acid+ magnesium = magnesium chloride + hydrogen.
What salts will sulphuric acid produce when reacted with metal?
It will always produce sulfate salts.
Sulfuric acid+ magnesium = magnesium sulphate + hydrogen.
What are metal oxides and metal hydroxides?
They are bases. Some of them are alkali.
This means they will always react with an acid to produce to salt and water.
What happens when ammonia is reacted with nitric acid?
Ammonium nitrate salt will be made but no water.
NH”3” + HNO”3” = NH”4”NO”3”
This is a good fertiliser.
How can a soluble salt be made with an insoluble base?
An acid plus a metal a metal hydroxide or oxide(insoluble bases)
If you want to make copper chloride mix copper oxide and hydrochloric acid.
Add the metal oxide or hydroxide or the acid. (It will be in powder form)
This will dissolve. Keeping adding it till nothing else dissolves.
Filter out the excess metal.
Evaporate off the water to get the salt.
How can a soluble salt be made using an alkali and acid?
First you react some acid and alkali them with an indicator. Measure out the amounts and stop when the indicator tells you it is neutral.
then do it again with out the indicator so the salt with have the right colour.
Evaporate the water away.
How is an insoluble salt made?
A precipitation reaction must take place.
Insoluble salts can sometimes be made by combining two solutions containing soluble salts.
Each solution containing one of the ions of the in soluble salt.
Filter the salt out, wash it with distilled water and leave it to dry.
What happens when an electric current goes through something ionic?
It has to be molten or in a solution but it will be broken down. This is called electrolysis.
What is an electrolyte?
The liquid that conducts electricity in electrolysis.
They must contain free ions. They’re usually the molten or dissolved ionic substance.
Explain the movement of electrons in electrolysis.
Electrons are taken away from ions in the anode and given to the ions in the cathode.
What is oxidation and reduction?
Oxidation is the loss of electrons and reduction is the gain of electrons. These two always happen in electrolysis.