1.1 and 1.3 (formulae and chemical equations) Flashcards
what does aqueous mean?
dissolved in water
What is the difference between copper sulphide and copper sulphate?
copper sulphate also has oxygen
Define compound
two or more different elements that are chemically bonded in a fixed proportion
what is a redox reaction?
a type of chemical reaction that involves a transfer of electrons between two species.
What oxidation state (charge) does group 1 always have?
+1 oxidation state
What oxidation state (charge) does group 2 always have?
+2 oxidation state
What oxidation state (charge) does group 0 always have?
0 as they don’t react so don’t form ions
What oxidation state (charge) does group 7 always have?
-1 oxidation state
What oxidation state (charge) do transition metals have?
they have different oxidation states
eg Fe(II) and Fe(III)
what does an oxidation agent do?
they will oxidise the other compound in the reaction
what does a reducing agent do?
they will reduce the other compounds in the reaction
what is the definition of electronegativity?
the ability of an element to attract a pair of electrons in a covalent bond
what is ionic bonding?
the electrons transfer from metal to non-metal
what is covalent bonding?
shared between atoms
what is metallic bonding?
delocalised electrons
when is the oxidation state of oxygen different?
in hydrogen peroxide and the xodiation state is -1
what is the oxidation state of flourine always?
always -1
what is meant by an isotope?
isotopes occur when atoms of the same element have different masses (i.e same number of protons, different number of neutrons)
How do you calculate the percentage composition calculations?
mass of element ÷ mass of compound x 100
define a mole
a mole is the amount of a substance in grams which has the same number of particles as there are atoms
what is avogadro’s constant?
6.02 x 10^23
what is the equation to work out mols?
mass divided by mr
define the term atom economy
a measure of the amount of starting materials that end up as useful products
how do you calculate the percentage atom economy?
relative formula mass of useful products divided by relative formula mass of all products x100
how much is 1 tonne in kg?
1000kg
how much is 1 tonne in g?
1,000,000g
define density
measures the amount of mass per unit of volume in a substance
calculate density
mass/volume
what are the three steps when converting density to concentration?
step 1 - no. of mols that you have in a solution n= m÷mr
step 2 - volume that the no. of mols is dissolved in
v= m ÷ d
step 3 - concentration
c= n ÷ v
what does the volume always have to be in when working out solutions?
dm3
define concentration
the amount of a substance dissolved in another substance
how do you get from gdm-3 to moldm-3?
÷mr
how do you get from moldm-3 to gdm-3?
xmr
how do you convert from the empirical formula to the molecular formula?
mr÷empirical mr
when working out calculations involving solutions what are the two equations you must remember and what are all the units?
m = n x mr
g = mol x no unit
n = c x v
mol = moldm-3 x dm3
what are some sources of error when reading the burette/pipette in titrations?
ensure you read the solution at eye level
allow the pipette to drain via gravity
what are some sources of error when using indicators?
people percieve colours differently
what are some sources of error when weighing solids?
residue could be left on the weighing scale/boat
may be spillage
what is the accuracy of a burette and how do you calculate the percentage error for it?
+/- 0.05cm3
2x0.05 / titre x100
what is the accuracy of a 2 d.p mass balance and how do you calculate the percentage error for it?
+/- 0.005g
0.005/mass x100
what is the accuracy of a 3 d.p balance and how do you calculate the percentage error for it?
+/- 0.0005g
0.0005/mass x 100
What are the four steps in the determination of xH2O?
- calculate mass of water removed
- mass of dry salt
- the moles of water and the moles of the hydrate
- divide mols of water by hydrate
How do you calculate percentage yield?
actual yield/theoretical yield x 100
(little/big)
What does avogadro’s law only apply to?
gases
what is important to know about double titrations?
in the first stage of the titration (phenolphthalein colour change) relates to the concentration of the hydroxide and carbonate
the second stage (methyl orange) relates to the conc of hydrogencarbonate
what is avogadro’s law?
equal volumes of gases at the same temperature and pressure contain equal numbers of molecules
What is 1 mole of any gass at room temperature
24.5m3
what is the difference between s.t.p and r.t.p? What is the volume of any gas at s.t.p?
room temperature and pressure (RTP) = 25 degrees celcius 298K and 1 atm (1.01x10^5 Pa)
standard temperature and pressure STP = 0 degrees celsius 273K and 1 atm pressure
what is the number of mols of a gas?
n = V/Vm
what is the ideal gas equation? and what are they measured in?
V = (RnT) ÷ P or PV = nRT
where P is in Pa
V in m^3
n in mols
T in K
R is molar gas constant, 8.31Jmol-1K-1
convert:
KPa to Pa?
1m3 to dm3
1dm3 to cm3
m3 to cm3
x1000
1m3 = 1000dm3
1dm3 = 1000cm3
1m3 = 1,000,000
what are volatile liquids?
liquids which turn into gas at not too high a temp
how do you calculate the molar mass of a gas (modifying the ideal gas equation)?
PV = mRT ÷ mr or mr = mRT÷ PV
what is Boyle’s law?
P1 x V1 = P2 x V2
(assume temp is constant)
what is Boyle’s law when the temperature is not constant?
P1 x V1 ÷ T1 = P2 x V2 ÷ T2
when a mass spectrometer is used to find the mr of an element what two things does it measure?
- mass of each different isotope of the element
- the relative abundance of each isotope of the element
what are the four steps of a mass spectrometer?
- ionisation
- acceleration
- deflection
- detection
what occurs in step one, ionisation?
vapourised sample passes into the ionisation chamber where the particles are bombarded w/a stream of electrons
what occurs in step two, acceleration?
an electric field accelerates the positive ions to a high speed
what occurs in step three, deflection?
different ions are deflected by a magnetic field by different amounts
what does the amount of deflection depend on?
the mass of the ion, lighter ions will deflect more
the charge of the ion, ions with two or more positive charges are deflected more
what occurs in step four, detection?
beam of ions passing through the machine is detected electrically
what are three other uses of mass spectroscopy?
- identifying unknown compounds eg testing athletes for drugs
- identifying trace compounds in forensic science
- analysing molecules in space
