1.8 Acids Bases & Salts Flashcards
The pH of Acids, Neutral & Alkalis
Acids have a pH of less than 7
Neutral solutions have a pH = 7
Alkalis have a pH greater than 7
To find the pH of a solution either
Use a glass rod to place a drop of the solution on universal indicator paper then compare the observed colour to pH meter
to find it more accurately a pH meter can be used. Gives data to at least one d.p.
Red litmus paper when an alkaline and acid is placed on it
Red litmus paper turns blue when an alkaline solution is placed on it.
Blue litmus paper turns red when an acidic solution is placed on it
Colour with universal indicator
Red - Strong Acid (e.g. Hydrochloric Acid )
Orange Yellow - Weak Acid (e.g. Ethanoic Acid)
Green - Neutral (e.g. Water)
Green Blue - Weak Alkali (e.g. Ammonia )
Purple - Strong Alkali e.g. (Sodium Hydroxide)
Advantages and Disadvantages of Universal Indicator Paper
Easy to use and cheap
Not accurate
Advantages and Disadvantages of pH meter
Gives accurate pH value
Expensive / needs calibrated before use
What is the concentration
The concentration of a solution is the number of moles of solute dissolved in dm³ of the solution
The units of concentration are
mol/dm³ (1dm³ = 1L)
What is an Acid
A substance that dissolves in water to produce hydrogen ions H⁺
A strong acid in water
A weak acid in water
A strong acid is completely ionised in water
A weak acid is partially ionised in water
The higher the concentration of hydroxide ions in an alkaline solution
The higher the pH
Alkalis dissolve in water to produce
Hydroxide Ions, OH⁻
A strong alkali in water
A weak alkali in water
A strong alkali is completely ionised in water
A weak alkali is only partially ionised in water
What is neutralisation
The reaction between an acid and an alkali to form a salt and water
Ionic equation for neutralisation
H⁺ + OH⁻ = H₂O
What is a base
A metal oxide or hydroxide that neutralises an acid to produce salt and water
What is an Alkali
A soluble base
If a base does dissolves in water we call it
An Alkali
Difference in Concentrated and Dilute solution
A concentrated solution contains a large amount of solute per dm³ of solution
A dilute solution contains a small amount of solute per dm³ of a solution
Risk assessment for the symbols
Corrosive
Toxic
Flammable
Caution
Corrosive - Safety glasses gloves and lab coat should be worn
Toxic - Contact should be minimised by using safety glasses
Flammable - No naked flames in laboratory
Caution - Care should be taken in handling to avoid spills
How to test for hydrogen
Apply a lighted Splint and a popping sound results
H₂ + O₂ —> 2H₂ + O₂ —> 2H₂0
How to test for Carbon Dioxide
Bubble gas through limewater. If the gas is CO₂ the limewater will change from colourless to milky.
What is a salt
A compound formed when some or all the hydrogen ions in an acid are replaced by metal ions or ammonium ions
Name of Salt produced
Hydrochloric Acid HCl-
Sulfuric Acid - H₂S04 -
Nitric Acid HN0₃-
Hydrochloric Acid HCl- Chloride
Sulfuric Acid - H₂S04 - Sulfate
Nitric Acid HN0₃- Nitrate
Reactions of Acids with Metals
And observations
Acids + Metal –> Salt + Hydrogen
Bubbles of Gas
Grey solid dissapears and solution remains colourless
Heat released
Reactions of Acids with Metal Hydroxides
Equation
Acid + Metal Oxide –> Salt + Water
Reactions of Acids with Metal carbonates and hydrogen carbonates
Equation And observations
ACID + METAL CARBONATE –> SALT + WATER + HYDROGEN CARBONATE
Bubbles of Gas
Heat released
