Module Six: Acid/Base Reactions Flashcards
(39 cards)
What is an acid?
A H+ donator, that has a pH lower than seven and can neutralise a base.
What is a base?
A H+ acceptor, with a pH higher than seven and can neutralise an acid.
What are some properties of acids?
- Sour taste
- Conducts electricity
- Turns blue litmus red
- pH <7
- Corrosive
What are some properties of a base?
- Bitter taste
- Soapy feel
- Conducts electricity
- Turns red litmus blue
- pH>7
- Corrosive
What is an alkali?
A base that can dissolve in water
What is the general equation for a neutralisation reaction?
acid + base –> salt + water
What is the general equation for an acid/carbonate reaction?
acid + carbonate –> salt + water + carbon dioxide
What is the general equation for an acid/metal reaction?
acid + metal –> salt + hydrogen gas
What are two everyday examples of neutralisation?
- Ant bite: formic acid and sodium hydrogen carbonate
- Heartburn: hydrochloric acid and magnesium hydroxide
What is an example of industrial neutralisation?
burning fossil fuels: limestone and SO2
How do you calculate the standard enthalpy of neutralisation?
1) Balance the equation
2) Determine the number of moles of H2O
3) Calculate the quantity of heat using q=mcAt
4) Calculate the enthalpy using nH=-q/n(water)
Outline Lavoiser’s theory
He proposed that oxygen was the component in a compound responsible for the compound being an acid. This was disproved as many acids do not contain oxygen
Outline Humphrey Davy’s theory
He proposed that oxygen could not be responsible for acidity. Led him to believe that H made substances acidic. Proposed acids contained H and could be replaced by metals.
Outline Arrhenius’ theory
Proposed that an acid was a substance that ionises in solution to produce H+. Proposed that a base was a substance that in solution produced OH-. Works well for aqueous solutions when organic solvent used. Can’t explain why NH4 is a base.
Outline the Bronsted-Lowry theory
Proposed that an acid is a substance that donated one or more H+ and a base is a substance that accepts one or more H+.
Outline Lewis’ theory.
Proposed that an acid is an electron pair acceptor and that a base is an electron pair donator. Explained why BF3 reactions with NH4.
What is a titration?
A volumetric technique where the concentration of an analyte is determined by neutralisation with a standard chemical.
What are the three primary purposes of a titration?
- Quantitative analysis
- Identification of an unknown substance
- Quality control
What is a primary standard solution?
One that has an accurately known concentration, and is used as the titrant in titrations.
A primary standard must be made from what?
A pure, stable, soluble solid
What is the equivalence point?
The point of a titration where the amount of titrant added is enough to completely neutralised analyte solution. They are both stoichematrically equal.
How do you determine how much mass you need for a primary standard?
1.Write out a balanced equation
2.Determine the concentration you want to use
3.Determine how many moles you will have using c=n/v
4.Calculate the mass using n=m/mm
What is the end point?
The point in which the indicator changes colour.
Why must you select the correct indicator?
-to match the pH
-for precision and accuracy
-to avoid over-titrations or under-titrations
