Chemistry revision November exam
Acids and Alkalis
All aqueous solutions are either acidic or alkaline or they can also be neutral
The acidity or alkalinity of a solution is measured on the PH scale. The PH scale measures from 1-14. 7 being neutral. The lower the PH the more acidic and if it is higher than 7 then it is more alkaline.
Bases and salts
Bases are a substance that neutralise acids to form a salt
Metal oxide + acid - salt + water
During neutralisation hydrogen ions in the acid combine with oxide ions to form water which removes hydrogen ions so the PH increases.
Bases are substances that neutralise acids to form a salt.
An ion is an atom that has been charged by losing or gaining electrons.
Polyatomic ions are formed when small groups of atoms are held together by covalent bonds.
Solubility
An insoluble substance is a substance that cannot be dissolved in a solvent even after mixing with something such as sand and water
A soluble substance is something that is easily dissolved in a solvent
Titration method
First what you need to do is use a pipette to measure out and alkaline solution and then add a few drops of an indicator such as methyl orange. Then you need to add an acidic solution to a burette. Then you use the pipette to add a few drops of an acid or a alkali then swirl the flaks till the solution is neutralised. Then you need to measure the amount of acid that was required to neutralise the alkali then you repeat this process a few times and then you find your mean result.
How to find copper sulfate
Get 20cm cubed of dilute sulphuric acid and put into a small chronicle flask. Then put it in a bath at 50 degrees Celsius. Then add copper oxide powder and if it is reacting with the acid and disappearing add more of it till it stops reacting with the acid. Then filter the solution and put into an evaporating basin. Then put on a beaker filled with water and heat it using a Bunsen burner and stop heating it when the crystals start to form. Then you put your solution into a watch glass and wait for all of the water to evaporate
Definitions
Dilute - Making a liquid thinner or weaker by adding a solvent to it.
Concentrated -
Indicators - Indictors in chemistry determines if a acid or alkali has neutralised by the change in colour or the alkali or acidic solution.