Chapter 4 Acids and redox Flashcards
What are acids
- When dissolved in water an acid releases hydrogen ions a protonss H+ into the solution
what is a strong acid
- releases all it’s hydrogen atoms into solution as H+ ion and completley dissociates in an aqueous solution
What is a weak acid
- only releases a mall propertion of it avilable hydrogen atoms into solution as H+ ions
- partially dissociates in an aqueous solution
What are the four common acids
- hydrochloric acid - HCl
- sulfuric acid - H2SO4
- nitric aci - HNO3
- ethanoic acid - CH3COOH
What are the four common bases
- metal oxides
- metal hydroxides
- metal caarbonates
- ammonia
What is a base
- neutralie an acid to form a salt
What is an alkali
- a base that dissolved in water releasing hydroxide ions OH- into the solution
What are 3 example of alkalis
- NaOH
- KOH
- NH3
What is a neutralisation reaction
- H+ ions (aq) ions from the acid react with a base to form a salt and neutral water
- H+ ions are replaced by metal of ammonium ions from the base
What are the type of salts formed from the 4 common acids
- hydrochloric acid - chloride
- sulfuric acid - sulfate
- nitric acid - nitrate
- ethanoic acid - ethanoate
Describe the neutralisation reaction between acid and metal oxide and hydroxides
- form salt and water
Describe the ionic equation for a neutralisation reaction
- H+(aq)+OH-(aq) -> H2O(l)
What is formed when an alkali reacts with an acid
- salt and water
Describe the neutralisation reaction between acids and carbonates
- form salt water and carbon dioxide
What is a titration
- ued to accuratley meaure the volume of a solution that reacts exactly with another volume
What are titrations used for
- finding the concentration of a solution
- identification of an ynknown chemical
- finding the purity of a substance - important in medicines ,food and cosmetics
What is a concordant result
- results are within 0.1cm3 of each other
Decribe how you would prepare a standard solution
- solid weighed accuratley
- solid is dissolved in a beaker using less distilled water than will bed needed to fill the volumetric flask to the mark
- this solution is transferred to a volumetric flask the last traces of solution is rinsed into a flask with distilled water
- flask carefully filled to the graduation line by adding distilled water a drop at a time yntil meniscus lines up exactly with the mark
- add stop and invert volumetric flask several times to mix up the solution - if not done titration will not be consistent
Describe the acid base titration procedure
- add a meaured volume of one solution to a conical flask using a pipette
- add the other solution to a burette and record intial burette reading nearest 0.05 cm3
- add a few drop o indication in concial flak
- run solution in burette into the solution in the conical flak swirling throughout until indicator change to enf point
- record the final burette reading
- trial titration carried out firt
- then titration is repeated until two accurate titres are concordant
Decribe the error of the pipette having an air bubble
the air could be releaed during titration leading to an error
What is an oxidation number
- baed on the set of rules that apply to atoms
- as the numner of electrons involved in bonding to a different element
What are the oxidation rules for elements
- zero for elements
- each atom in a compound ha an oxidation number
What are special case of oxidation numbers
- H in metal hydrides - -1-NaH,CaH2
- O in peroxides - -1-H2O2
- O bonded to F - +2-F2O
What are redox reactions
involves both reduction and oxidation
