C4 Acids And Redox Flashcards
Which base is used to treat acid ingestion
Magnesium hydroxide
How are ammonium salts formed
When acid reacts with aqueous ammonia
What do acids do when dissolved in water
Release H+
What is a strong acid
Completely dissociates in aq to release all its H+
Why is a reversible arrow used to show the dissociation of a weak acid
The forward reaction is incomplete
What is a weak acid
Partially dissociates in aq to releases H+
What is a strong base
Base that dissociates 100% in water
What is a salt
The product of a reaction in which the H+ ions from the acid are replaced by metal or ammonium ions.
What is an alkali
Soluble base that dissociates in aq to release OH-
What is a base
An insoluble compound that neutralises an acid to form a salt.
Acid + metal hydroxide/oxide
Salt + water
Acid + alkali
Salt + water
Acid + carbonate
Salt + CO2 + H2O
What is titration
Used to accurately measure vol of 1 solution that reacts exactly with another solution
What can titrations be used for
Finding conc of solution
Identification of unknown chemicals
Finding purity of a substance
What’s a standard solution
A solution of known concentration
Method to prepare a standard solution
Weigh (s) accurately
Dissolve (s) in beaker using less distilled water than need to fill volumetric flask to the mark
Transfer this to volumetric flask, and rinse last traces of solution into flask with distilled water
Carefully fill flask to graduation line by adding distilled water drop wise until the bottom of the meniscus lines up exactly with the mark.
View graduation mark and meniscus at eye level for accuracy
Invert volumetric flask several times to mix solution thoroughly - this stage is important to keep titration results consistent
Method for acid-base titration
Add measured vol of 1 solution to conical flask using pipette
Add other solution to burette + record initial burette reading to nearest 0.05cm^3
Add few drops of indicator to solution in conical flask
Run solution in burette into solution in conical flask
swirling conical flask throughout to mix two solutions.
Eventually indicator changes colour at end point of titration.
end point used to indicate vol of 1 solution that exactly reacts with the vol of 2nd solution.
Record final burette reading.
vol of solution added from burette is called
titre, calculated by subtracting initial from final burette reading.
quick, trial titration carried out 1st to find approx titre.
titration then repeated accurately, adding solution dropwise as end point is approached.
Further titrations carried out until 2 accurate titres are concordant - agreeing to within 0.10 cm3
What is an oxidation number
Number of electrons an atom uses to bond with any other atom
What is the oxidation number of oxygen in peroxides
-1
E.g. H2O2
What is the oxidation number of uncombined elements
0
What is the oxidation number of a simple ion
Charge on the ion
When an element has more than 1 stable oxidation number how is it indicated
Written as a roman numeral
What’s the oxidation number of Fe in iron (III) chloride
+3
What are oxyanions
Negative ions that have an element along with oxygen
Define oxidation in terms of electron transfer and oxidation number
Loss of elctrons
Increase in oxidation number
Define reduction in terms of electron transfer and oxidation number
Gain electrons
Decrease in oxidation number
What is a redox reaction
Reaction in which both oxidation and reduction takes place
Is the sign in oxidation number placed after or before the number
Before the number
E.g. -2 , +1 , +3
What’s the oxidation number of oxygen in metal hydrides
-1
E.g. NaH , CaH2
What is the oxidation number of oxygen bonded to fluorine
E.g. F2O
+2
What does a roman numeral show
Shows oxidation state of the element, without a sign
E.g. iron(II) = Fe +2
iron (III) = Fe +3
Oxidation number of N in nitrite
NO2^-
+3
Nitrate(III) = modern name
Oxidation number of N in nitrate
NO3^-
+5
Nitrate(V) = modern name
Metal + acid
Salt + hydrogen
What does the sum of oxidation numbers equal
Total charge
