Topic 4 - chemical changes Flashcards
What is produced when an acid and a base react together?
Salt + Water
H+ + OH- =
H2O
Describe how to carry out a titration.
Use a pipette to add a set volume of the alkali to a conical flask and add a couple of drops of indicator. Use a funnel to fill a burette with some acid of known concentration. Record the initial volume of the acid in the burette. Open the burette tap to add the acid to the alkali in small amounts at a time while swirling the conical flask. Slow down when you reach close to the end point. Indicator changes colour when all the alkali has been neutralised. Record the final volume of acid in the burette and use that and the initial volume to calculate the volume of acid used to neutralise the alkali.
Name the three indicators used in titration and the colour they turn in acids and alkalis.
Phenolphthalein - colourless in acids, pink in alkalis
Litmus - red in acids, blue in alkalis
Methyl orange - red in acids, yellow in alkalis
Why should titrations be repeated?
To increase accuracy of the readings. To be able to calculate a mean. To remove anomalous results.
Describe how to make soluble salts using an insoluble base.
Pick out the right acid and an insoluble base. Gently warm the dilute acid using a bunsen burner, then turn off said bunsen burner. Add the insoluble base a little bit at a time. Filter out the excess solid to obtain the salt solution. Then gently heat the salt solution using a water bath to evaporate some of the water then leave the solution to cool. Crystals of the salt should form which can be filtered from the solution and pat dry.
What is the mnemonic for the reactivity series?
Please Say Little Children May Control Zealous Intents Having Control
Acid + Metal =
Salt + Hydrogen
Metal + Water =
Metal hydroxide + Hydrogen
What does OILRIG stand for?
Oxidation Is Loss Reduction Is Gain
Why is gold not found as an ore?
As it is too un-reactive to become oxidised
What are REDOX reactions?
When reduction and oxidation occur at the same time
