1.12 Acids & Bases Flashcards
The following are general equations you need to be able to recall and apply to real examples:
*State the products formed
Type 1 - Acid + Metal –>
Type 2 - Acid + Metal –>
Type 3 - Acid + Metal Hydroxide –>
Type 4 - Acid + Metal Carbonate –>
Type 1 - Salt + Hydrogen
Type 2 - Salt + Water
Type 3 - Salt + Water
Type 4 - Salt + CO2 + Water
Define a base
Define an acid
acid : proton donor
base : proton acceptor
What does it mean if hydrogen is labelled as amphoteric
Water can act as a base or an acid
Major difference between strong and weak acids
Strong acids fully dissociate, weak partially dissociate
What acids are you expected to know are strong
HCl
H2SO4
HNO3
H3PO4
What acids are you expected to know are weak
All carboxylic acids are weak
How can you re-write pKa
Ka = 10^-Pa
State method for using titration to find concentration of an acid
- one of reagents must be in standard solution
method :
(1)Fill a burette with the acid of know concentration.
(2)Accurately measure out 25cm3 of the alkali standard solution using a pipette and transfer to a conical flask.
(3)Add a few drops of a suitable indicator to the alkali.
(4)Slowly add the acid from the burette into the conical flask, swirling constantly. As soon as the indicator changes colour the solution has turned neutral so stop adding the acid. Record the volume of acid which has been added.
(5)Repeat the process until you get two results which are within 0.1cm3 of each other. The mean of these two results are then used to calculate an average titre. - Once an average titre has been determined it can be used to calculate the unknown concentration.
State how you can use a pH probe to measure the pH of a solution as it changes as a base is added to an acid
The process involves the following steps:
(1) Measure the pH of the acid solution and record.
(2) Add 1cm3 of the base solution
(3) Stir the mixture
(4) Measure the pH and record.
(5) Repeat the process until the base is in excess.
(6) Add base in smaller increments near the end point
What is meant by the equivalence point
when exactly enough acid has been added to neutralise the base (or vice versa). Mid-point on the vertical section of the graph
What is meant by the end point
the exact volume of acid or base which needs to be added to cause an indicator to change colour.
What are indicators used for
- they help show when a neutrlisation reaction is complete
- Typically indicators are one colour in acidic conditions, another colour in basic conditions, and so during a titration the moment an indicator changes colour tells us that the reaction mixture is neutral.
What is buffer solution
a solution which can resist change in pH when a small amount of acid or base is added
What is an acidic buffer
made of weak acid and a soluble salt of that acid
It maintains a pH below 7
What is a basic buffer
made of a weak base and a soluble salt of that base
It maintains a pH above 7
Define half-neutralisation point
- The point at which enough base has been added to neutralise exactly half of the acid
