Chemical Changes: Acids and Bases
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The lower the pH the more _______.
acidic
The higher the pH the more _________.
alkaline
What pH will a neutral substance have? What is an example of a substance which is neutral?
A neutral substance has a pH of 7. e.g. pure water
What is a base?
• has a pH above 7 • reacts with an acid to form a salt
What is an acid?
• forms H+ ions in water • has a pH of less than 7
What is an alkali?
• a type of base that is soluble in water • this forms a solution with a pH greater than 7 • forms -OH ions in water
What is the reaction for neutralisation?
acid + base → salt +water
What is the ionic equation for neutralisation?
H+(aq) + -OH(aq) → H2O(l)
What is the pH scale?
The measure of acidity/alkalinity of a solution.
What is a strong acid and a weak acid ?
A strong acids completely dissociate in solution whereas weak acids do not fully dissociate in solution.
What happens to pH as the concentration of H+ increases?
the pH decreases
What is a concentrated acid and what is a dilute acid?
Concentrated acids have more moles of acid per unit volume than dilute
How is a concentrated acid different to a strong acid?
Strength refers to whether the acid is completely ionised/dissociated in water or partially. Concentrated acid refers to having more moles of acid per unit volume.
As the pH is decreased by one unit, what change is seen in the hydrogen concentration?
Increases by a factor of 10
Name the following salts: LiNO3, K2CO3, MgBr2, BaSO4.
• lithium nitrate • potassium carbonate • magnesium bromide • barium sulfate
What happens to the proportion of H+ as pH increases by 1?
proportion of H+ decreases by 10x
Is the ionisation of a strong or weak acid reversible?
weak