Chapter 4 - Acids and Redox Flashcards
What is an acid?
Proton donor
What is a base?
Proton acceptor
What is a strong acid?
Proton donor that completely dissociates in aqueous solution
What is a weak acid?
Proton donor that partially dissociates in aqueous solution.
What is an alkali?
A base that dissolves in water, releasing hydroxide (OH-) ions into the solution.
What is the word equation for neutralisation of acids with metals?
MASH - Metal + Acid —> Salt + Hydrogen
What is the word equation for neutralisation of acids with metal oxides?
Metal Oxide + Acid —> Salt + Water
What is the word equation for neutralisation of acids with metal hydroxides?
Metal Hydroxide + Acid —> Salt + Water
What is the word equation for neutralisation of acids with metal carbonates?
Metal Carbonate + Acid —> Salt + Water + Carbon Dioxide
What is the word equation for neutralisation of acids with alkalis?
Acid + Alkali —> Salt + Water
What is a titration?
A technique used to accurately measure the volume of one solution that reacts completely with another solution.
What are the uses of titrations?
Finding concentration of a solution
Identifying unknown chemicals
Finding the purity of a substance
What are concordant results?
Results that are within 0.10cm3 of each other
When can a mean titre be calculated?
When 2 or more concordant results are obtained
When is the oxidation number zero?
When elements are by themselves or bonded to the same element.
What is the oxidation number of Hydrogen?
+1 with non-metals
-1 with metals
What is the oxidation number of Oxygen?
always -2
except H2O2 where it is -1
What is the oxidation number of group 1 and 2 metals?
Usually +1 and +2
What is the oxidation number of halides?
-1 unless bonded with oxygen where it can go positive.
Fluorine is always -1
What is oxidation and reduction?
OILRIG - Oxidation is loss of electrons, reduction is gain of electrons
What is oxidation and reduction in terms of oxidation number?
Oxidation is increase in oxidation number, reduction is decrease in oxidation number
How to make a standard solution?
- Weigh solid using mass balance and dissolve in beaker. Use less distilled water than what would fill up to the mark of a volumetric flask.
- Transfer solution to volumetric flask. Rinse the last traces of solution into the flask using distilled water.
- Fill the flask up to the graduation line one drop at a time until the bottom of the meniscus lines up with the mark. View the flask from eye level for accuracy.
- Slowly invert the volumetric flask to mix the solution.
Why does the bottom of the meniscus have to line up with the mark?
If it is above the mark, then the solution will be too diluted and won’t be the correct concentration.
Why is the flask inverted?
To mix the solution so that the concentration is consistent throughout the solution. This stops us from getting incorrect titration results.
What is the method for a titration experiment?
- Using a pipette, add a measured volume of one solution to the conical flask and put a few drops of indicator in it.
- Add the other solution to the burette and record the initial burette reading to the nearest 0.05cm3.
- Slowly add the solution in the burette to the solution in the conical flask and swirl continuously.
- Stop swirling and close the burette when the end point is reached. Record the new reading on the burette.
- A trial is carried out to find the approximate titre.
- Repeat the titration until concordant results within 0.10cm3 of each other are obtained.
What does the end point indicate?
The volume of one solution that exactly reacts with the volume of the second solution.
What is the word equation for a reaction between a metal and water?
Metal + Water —> Metal Hydroxide + Hydrogen
How do we remove air bubbles from the burette prior to experiment?
Run the solution out through the tap until all air bubbles are removed.
What does the end point indicate?
The volume of one solution that exactly reacts with the volume of the second solution.
