1) Chemical Changes Flashcards
what are acids in solutions sources of?
hydrogen ions H+
what are alkalis in a solution sources of?
hydroxide ions OH-
what is the pH of acidic solutions?
lower than 7
what is the pH of alkalis solutions?
above 7
what colour is litmus in different acid, neutral and alkalis solutions?
acid= red neutral= purple alkalis= blue
what colour is methyl orange in different acid, neutral and alkalis solutions?
acid= red neutral= yellow alkalis= yellow
what colour is phenolphthalein in different acid, neutral and alkalis solutions?
acid= colourless neutral= colourless alkalis= pink
the higher the concentration of hydrogen ions in an acid solution…
the lower the pH
the higher the concentration of hydroxide ions in an alkaline solution…
the higher the pH
what is the method for investigating the neutralisation reaction between calcium oxide(base) ad adult hydrochloric acid?
- measure out dilute hydrochloric acid into conical flask
- measure fixed mass of calcium oxide, scales
- add together
- wait for base to completely react, record pH
- repeat 2-4 until all acid reacted
- plot graph to see how pH changes with mass of base added
what is concentration?
- how much acid there is in al litre 1dm3 of water
- how watered down the acid is
what is dilute?
acid with small number of acid molecules compared to volume of water
what is a strong acid?
- ionise almost completely in water
- hydrocloric acid, nitric acid, sulfuric acid
what is a weak acid?
- do not fully ionise in solution
- citric acid, carbonic acids
what is a base?
any substance that reacts with an acid to form a salt and water only