Acids and solutions. Flashcards
What happens when an acid is dissolved in water?
Releases hydrogen ions as protons(H+) into the solution.
Strong acid definition.
Releases all of it’s hydrogen atoms into the solution as H+ ions and completely dissociates in an aqueous solution.
Weak acid definition.
Only releases a small proportion of it’s available hydrogen atoms into solution as H+ ions-partially dissociates in aqueous solution.
Base definition and examples.
Metal oxides, metal hydroxides, metal carbonates and ammonia.
Neutralises an acid to form a salt.
Alkali definition.
A base that dissolves in water releasing hydroxide ions(OH-) into the solution.
Ionic equations.
PRACTICE QUESTIONS.
W/ Sulfuric acid too.
Common alkalis/bases.
NaOH-sodium hydroxide.
KOH-potassium hydroxide.
NH3-ammonia.
Common acids formulae.
HCL-hydrochloric acid.
H2SO4-Sulfuric acid.
HNO3-nitric acid.
CH3COOH-ethanoic acid(ethanoate as a salt).
What happens in neutralisation?
H+ ions react w/ OH- ions to form H2O.
And a salt.
H+ ions from acid replaced by metal or ammonium ions from base.
Neutralisation of acids w/ metal oxides and hydroxides.
Forms a salt and water only.
Practice equations.
Neutralisation of an acid w/ an alkali.
Reactants are in solution.
Acid+alkali–>salt+water.
H+(aq)+OH-(aq)–>H2O(l).
Neutralisation of acids w/ carbonates.
Metal carbonate+acid–>Salt+water+carbon dioxide.
What is a titration used for?
Measure the volume of acid that completely neutralises an alkali.
Find the concentration of a solution.
Identifying unknown chemicals.
Finding purity of a substance.
Procedure for preparing a standard solution(solution of known concentration).
Weigh solid accurately.
Dissolve in beaker using less distilled water than is needed to fill the volumetric flask to the mark.
Transfer solution to volumetric flask.
Swill beaker with distilled water and pour into flask to ensure all solid is in flask.
Fill flask dropwise to graduation line.
Until bottom of meniscus lines up exactly w/ mark.
At eye level.
Re-do if goes over line.
Slowly invert flask several times to mix(titrations will not be consistent w/o this step).
Procedure for acid-base titrations.
Add measure vol of one solution to conical flask w/ pipette.
Add other solution to burette and record initial reading to nearest 0.05cm3.
Add few drops of indicator to conical flask.
Run burette solution into conical flask solution.
Swirl flask throughout to mix.
Indicator will change colour at end point-indicates volume of one solution that exactly reacts w/ the volume of the second solution.
Record final burette reading.
Volume added from burette=titre.
Quick, trial titre first=approximate titre.
Repeat accurately.
Add solution dropwise as endpoint is approached.
More titrations until 2 accurate, concordant tires are reached(within 0.10cm3).
Only use most accurate titres(0.1cm3) in mean to get accurate results.
Discard far off measurements.
