2.1.4 Acids Flashcards
What is an acid
- proton donors
- contains hydrogen in it
- when dissolved in water, the acid release H+ ion in to the solution
Eg HCl + H2O —> H+ + Cl-
What is a strong acid and give an example
When the acid release all its hydrogen atoms into the solution as H+ ions and !completely dissociates! In an aqueous solution
Eg hydrochloric acid HCl
HCl —> H+ + Cl-
What is a weak acid and give an example
When the acid release a small proportion its available hydrogen atoms into the solution as H+ ions and !partially dissociates! In an aqueous solution
Eg ethanoic acid CH3COOH
CH3COOH <=> H+ + CH3COO-
(Equilibrium indicates incomplete reaction)
What are examples of bases
- metal oxide
- metal hydroxide
- metal carbonate
- ammonia
What is a base and What does a base do
It is a proton accepter,
It neutralises an acid to form a salt
They can be metal oxides, metal carbonates or metal hydroxides (alkali)
What is an alkali and give an example
Metal hydroxide
It’s a base that dissolves in water releasing hydroxide ions (OH-) into the solution
Eg NaOH + H2O —> Na+ + OH-
Dissociation in sulphuric acid
Sulfuric acid initially only loses one of its h atoms so behaves as a strong acid but then behaves as a weak acid. This can be seen as a similar process in other acids containing more than one hydrogen.
Eg H3PO4 —> H+ + H2PO4-
H2PO4- —> H+ + HPO4-2
HPO4-2 —> H+ + PO4-3
What can titration be used for?
- Finding the concentration of a solution
- Identification of unknown chemicals
- Finding the purity of a substance
How much is the volumetric flask filled?
The bottom of the meniscus of the liquid should be touching the graduation line
What is the uncertainty of the burette? And how to calculate % uncertainty of a titre
Titre. x 100
Equation and name of salt for MgO + HCl
MgO + 2HCl —> MgCl2 + H2O
Magnesium chloride
What is an acid salt?
When one hydrogen atom has been replaced by a metal ion, but the other hydrogen atom can still behave as an acid
How To carry out a titration
- Using a pippet Rinsed with alkali measure 25cm³ of a solution and add it to a conical flask with an indicator
- Add other solution into a burette till zero
- slowly open the tap while swirling the flask until the colour change slows down
- add drop by drop until endpoint is reached
- repeat until concordant results (0.1cm3)
what is and How to prepare a standard solution
- it is A solution of known concentration
- Weigh the solid accurately
- dissolve in distilled water in a beaker
- pour into a volumetric flask rinsing the beaker with more distilled water making sure to fill till exactly the graduation line for accuracy (250cm3)
(view at meniscus at eye-level) - invert flask several times for consistency of mixture
What happens in a neutralisation reaction?
The H ions react with a base to form a salt and water
Hydrogen in the acid is replaced by a metal or ammonium ion to form a salt
CuO + H2SO4 —> CuSO4 + H2O
exception - NH3(aq) + HCl(aq) → NH4Cl(aq)
no water is produced
Hydrochloric acid and sodium hydroxide react, what is the salt?
Sodium chloride
Sulphuric acid and copper oxide react what is is the salt formed
Copper sulphate
Nitric acid and calcium carbonate react, what is the salt?
Calcium nitrate
Ethanolic acid and ammonia react what is the salt?
Ammonium ethanoate
Equation and name of salt for NaOH + H2SO4
2NaOH + H2SO4 —> Na2SO4 + 2H2O
Equation and name of salt for ZnCO3 + HNO3
ZnCO3 + 2HNO3 —> Zn(NO3)2 + H2O + CO2
Zinc nitrate
Equation and name of salt for NaOH + CH3COOH
CH3COONa + H2O
Right equations for partial and complete neutralisation of carbonic acid with sodium hydroxide
H2CO3 + NaOH —> NaHCO3 + H2O
H2CO3 + 2NaOH —> NaCO3 + 2H2O
Acid + metal carbonate =
Salt + H2O + CO2
Full equation: HCl + NaOH —> NaCl + H2O
What is the ionic equation?
H+ + OH- —> H2O
CL is a spectator ion
Acid and metal
Salt and hydrogen
What are the main acids?
HCl hydrochloric acid
H2SO4 sulphuric acid
HNO3 nitric acid
CH3COOH ethanoic acid
H3PO4 phosphoric acid
What are the common alkalis?
NaOH sodium hydroxide
KOH potassium hydroxide
NH3 ammonia
What does the dot formula indicate?
The amount of water present in a crystalline structure
what is the systematic name of?SnCl2
Cl-1 x 2 = -2 Sn = +2 so II
Tin(II) chloride
How to work out percentage uncertainty given the initial and final readings
- Work out the difference (=the titre)
- Divide the uncertainty by the titre
- X by 2 as there’s 2 values which go wrong
- X by 100 for a percentage
What do the the Roman numerals in the name of a compound represent
The charge of the ion they are next to
How can we obtain a solid from a mixture
Filter it out and evaporate/ dry
write The reaction of ammonium carbonate with dilute nitric acid
(NH4)2CO3 + 2HNO3 → 2NH4NO3 + CO2 + H2O
20.25 20.35 20.60 Calculate the mean titre
20.25+20.35/2 = 20.30 cm3
Writing equation and oxidisation numbers of CH3COOH with magnesium, What has been oxidised and what has been reduced
Include the Ionic equation
Mg + 2CH3COOH → (CH3COO)2Mg + H2
Mg + 2H+ → Mg2+ + H2
Oxidation: Mg from 0 to +2 Reduction: H from +1 to 0
Explain why two different reactions with magnesium one with HCL and one with CH3COOH produce the same volume as gas at different rates
HCL is a strong acid which completely dissociates It has a greater concentration of H So has more frequent collisions therefore faster rate of reaction compared to ethanolic acid To produce the same moles of H in the end as ethanoic acid has a lower concentration and is a weak acid which partially dissociates
