2.1 - Atoms and reactions Flashcards
Define isotope
atoms of same element with the same no. protons + electrons but different no. of neutrons, different masses and different physical properties
Define relative isotopic mass
mass of an atom of an isotope compared with 1/12th mass of a carbon-12 atom
Define relative atomic mass
weighted mean mass of an atom compared with 1/12th mass of a carbon-12 atom
Define amount of substance
quantity of a substance present in a sample
Give the formulas of the following ions: nitrate, carbonate, sulfate, hydroxide, ammonium, zinc, silver
NO3-
CO3 2-
SO4 2-
OH-
NH4+
Zn2+
Ag+
Define mole
unit for amount of substance
Define Avogadro constant
no. of particles in a mole
Define molar mass
mass per mole of a substance
units: gmol-1
Define molar gas volume
volume of 1 mole of gas
units: dm3mol-1
Define empirical formula
simplest whole number ratio of atoms of each element present in a compound
Define molecular formula
number and type of atoms of each element in a molecule
Define water of crystallisation
water molecules that form part of a crystalline structure of a compound
State the ideal gas equation and the units for each part
pV=nRT
p in Pa
V in m3
T in K
Describe the sustainable benefits of chemical processes with a high atom economy
- reduced costs
- less waste
Explain what makes an acid strong or weak
- strong: fully dissociates in solution
- weak: partially dissociates in solution
Describe the techniques and procedures when preparing a standard solution
- weigh mass of crystals using a balance with 2 or more decimal places
- dissolve in distilled water and stir with glass rod
- transfer to 250cm3 volumetric flask using funnel
- rinse beaker, glass rod and funnel using distilled water and transfer washings to flask
- make up to mark with more water using a dropping pipette so that bottom of meniscus is on mark
- add stopper and invert several times to mix
Describe the techniques and procedures when carrying out an acid-base titration
- use graduated pipette and pipette filler to transfer 25cm3 standard solution to a 250cm3 conical flask
- add two drops of indicator (methyl orange or phenolphthalein)
- fill burette with acid e.g HCl and record initial reading
- open tap and add to conical flask until end point is reached (colour change), drop wise at end
- record final burette reading and calculate titre
- repeat until concordant results obtained and calculate mean using only concordant titres
Define alkali
releases OH- ions in aqueous solution
Define acid
releases H+ ions in aqueous solution
Define standard solution
solution of known concentration
Define base
substance which readily accepts H+ ions
What are concordant results?
titres within 0.1cm3 of each other
Give the colour changes for methyl orange and phenolphthalein
Methyl orange: yellow (alkali), orange (acid)
Phenolphthalein: pink (alkali), colourless (acid)
Define oxidation
loss of electrons
Define reduction
gain of electrons
Define disproportionation
redox reaction when same element is oxidised and reduced
Why may theoretical yield not be obtained?
- reaction not completed
- side reactions may take place
- purification may lead to loss of product
Suggest two modifications to a method that can reduce % uncertainty
- use a larger mass
- use balance which weighs to more decimal places
How to obtain a sample of ionic compound after reaction with acid?
- filter using funnel and filter paper to obtain solid
- dry
Criteria for neutralisation reaction?
H+ + OH- -> H2O
or
acid + base
