Acids & Redox Flashcards
When an acid is added in water what ion is released into the solution?
H+
Define acid
Proton donor
Describe the dissociation of a strong acid.
Fully dissociates
Define base
Proton acceptor
What are alkalis?
Bases that can dissolve in water to form OH-
What is formed when acid reacts with carbonate?
Salt, carbon dioxide and water
What is a salt?
A compound that is formed when H+ is replaced by a metal ion
What is formed when acids react with oxides?
Salt and water
What is formed when acid reacts with alkali?
Salt and water
What is formed when acids react with metals?
Salt and hydrogen
Why are the products the same when both alkalis and oxides react with acid?
They’re both bases
What does a dot formula indicate?
Water of crystalisation
What is an oxidation number?
The number of electrons an atom uses to bond with any other atom
What is the oxidation number of an uncombined element?
0
What is the oxidation number of oxygen in a combined element such as H2O?
-2
What is the oxidation number of oxygen in peroxides?
-1
What is the oxidation number of combined hydrogen such as NH3?
+1
What is the oxidation number of combined hydrogen such as NH3?
+1
What is the oxidation number of combined hydrogen in metal hydrides?
-1
What is the oxidation number of a simple ion?
Example Na+ = +1
Define oxidation in terms of electrons and oxidation number.
Loss of electrons and an increase in oxidation number
Define reduction in terms of electrons and oxidation numbers.
Gain of electrons and decrease in oxidation number
What are the formula of 4 common acids?
hydrochloric acid -> HCl
sulphuric acid -> H2SO4
nitric acid -> HNO3
ethanoic acid -> CH3COOH
What are the formulae of 3 common alkalis?
sodium hydroxide -> NaOH
potassium hydroxide -> KOH
ammonia -> NH3
How do you prepare a standard solution in an acid-based titration?
- Solid is weighed accurately
- Solid dissolves in a beaker with distilled water, less than what is needed to fill flask
- Solution is transferred to a volumetric flask (traces are rinsed with distilled water into the flask)
- Flask filled to the graduation line by adding distilled water a drop at a time until the bottom of the meniscus lines up exactly at eye level (if over solution must be prepared again)
- Flask slowly inverted many times to mix solution thoroughly (if not done titration results will be inconsistent)
How do you prepare a titration?
- Fill the burette with the standard solution
- Use a pipette filler to transfer 25cm3 of HCL to the conical flask
- Add 3 drops methyl orange
- Record initial burette reading
- Titrate the contents of the conical flask by adding the solution from the burette into the conical flask until a colour change
- Record the final burette reading and calculate the titre volume
- Repeat until 2 concordant results are reached
What’s one way of reducing uncertainties in a titration?
Increase the titre volume
What is an oxidising agent?
Accepts electrons from what is being oxidised, therefore it gains electrons and is reduced
What is an oxidising agent?
Accepts electrons from what is being oxidised, therefore it gains electrons and is reduced
What is a reducing agent?
Donates electrons to what is being reduced, therefore it loses electrons and is reduced
What is a disproportionate reaction?
When a species is both oxidised and reduced
What is uncertainty?
A reading for a specific instrument is said to be plus or minus half of the
smallest division.
What is the equation for uncertainty?
uncertainty/reading *100
uncertainty/reading 1002 only if there’s 2 readings
What is the method to calculating an unknown concentration?
- From the titration results calculate the amount of moles of one of the alkali
- Using the equation find the moles of the acid
- Work out the unknown concentration
What are the steps to identifying an unknown carbonate?
- Calculate the amount of moles of HCl that reacted, using the mean titre and concentration of HCl
- Determine the amount of X2CO3 that reacted using the equation
- Scale up to find the amount of X2CO3 in the 250cm3 solution prepared
- Find the Mr of X2CO3, then find the Mr of X