2.1 - Atoms and reactions Flashcards
(30 cards)
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
