Mrs Flashcards
Formulae for hydrochloric acid
HCL
Formulae for sulphuric acid
H2SO4
Formulae for nitric acid
HNO3
Formulae for ethanoic acid
CH3COOH
Formulae for ammonia (gas)
NH3
Formulae for carbon monoxide
CO
Formulae fro carbon dioxide (gas)
CO2
Formula for methane (gas)
CH4
Formulae for sulphur dioxide
SO2
What is the mass of an electron
1 / 1836
1 / 2000 th
What is the difference between the chemical properties of isotopes?
There aren’t any all isotopes are identical
Isotope calculation
( isotope mass x abundance ) + ( isotope mass x abundance ) / 100
how to make a standard solution?
1) weigh solution needed in a weighing boat
2) transfer solute in a glass beaker & rinse weighing boat with distilled water
3) swill solution, so solute is dissolved
4) pour solution into a volumetric flask
5) rinse the beaker and funnel, multiple times 2/3
6) place stopper on volumetric flask and shake
7) fill the flask up to the line with distilled water
8) invert & shake the flask
important points about standard solutions? the solute must:
- be available in a very pure form
- be stable over a long period of time
- not decompose when dissolved in water
- not absorb H20 or CO2
-not be volatile
what is stoichiometry?
ratio between the number of moles of substances taking part in a reaction
standard solutions are always…
an exact amount
what are moles and gases relationship?
mole of any gas has the same volume under the same conditions of temperature and pressure.
moles and gases at room temperature?
at room temperature and pressure, a mole of gas takes up 24000cm3 (24dm3)
moles and gas equation
volume = moles x 24 ( or 24000)
what are the features of ideal gases?
- particles have no volume
- collisions are elastic
- no interactions between particles
when do real gases behave like ideal gases?
- at high temperatures
- at low pressures
what are kelvins?
temperature scale designed so that -273 degrees is 0 kelvins
how to convert kelvins into degrees and back?
K = degrees + 273
degrees = K - 273
what is the ideal gas law?
p v = n R T
p = pressure (pa)
v = volume (m3)
n = number of moles
R = constant, 8.31 JK-1mol
T = temperature (K)
ideal gas law rearranged to find the number of moles?
n = p v / R T
ideal gas law rearranged to find the volume?
v = n R T / p
how to change cm3 and dm3 into m3
cm 3 = x 10-6
dm3 = x 10-3
Errors in titration and their effect
Leaving in a filter funnel
Could have liquid which drops into burette once you have started your titration
Effect: lowers final titre volume
Errors in titration and their effect
Bubble under tap
Liquid must fill this space before being added to the conical flask
Effect: increases final titre volume
Errors in titration and their effect
Ensure a conical flask is used
To ensure no loss of liquid whilst swirling
Errors in titration and their effect
Not swirling constantly
Chemicals not fully mixed
Effect: increase in final titre volume
Errors in titration and their effect
Not washing sides of conical flask just before end point
Due to splash back, reagents may be on one side of the flask and not in the mixture
Percentage % uncertainty equation
Error value / quantity measured x 100
If a weighing boat is measured and then re weighed later, how many error readings will there be?
2 error readings
Have to x 2
How to find the overall error in your experiment
Add all the % errors together
Brunettes error are:
- reading the burette at the start of this titration, half a division = +- 0.05cm3
- reading the burette at the end if the titration, half a division = +- 0.05cm3
- judging the end point to within one drop, volume of a drop = +- 0.05cm3
Total = +-0.15cm3
What is the uncertainty of a 25cm3 pipette
+- 0.1cm3
What is the uncertainty of a 25cm3 measuring cylinder
+- 0.5cm3
what is the empirical formula
simplest whole number ratio of atoms of each element in a compound
what is the molecular formula
actual number of atoms of each element in a compound
hydrated compounds
4
5
7
tetrahydrate
pentahydrate
heptahydrate
what is atom economy
measure of the proportion of reactant atoms that become part of the desired product in the balanced chemical reaction
% atom economy
molecular mass of desired product/ sum of molecular masses of all reactants
x 100
economic advantages of atom economy
- efficient use of its raw materials
- less waste products for a firm
environmental/ethical advantages of atom economy
- less raw materials, means less waste
- limited supply is more efficient
- less waste chemicals produced, which are often harmful to the environment
- more sustainable
- cheaper
theoretical yield
mass of product that should be formed in a chemical reaction. it assumes no chemicals are lost in the process
actual yield
the mass of the product actually formed through experiment
(yields may be given in moles or mass)
theoretical yield equation
moles = mass (theoretical) / Mr
percentage yield
actual yield / theoretical yield
x 100
reasons for reduced yield
- not all starting chemicals react fully
- reaction’s are reversible
- loss of chemicals during transfers between containers or filter paper
-other products are formed
Why is a back titration used
Substances that are insoluble in water can’t be directly titration, am indirect method (back titration) is used
% purity equation
Mass / mass of sample (stated in the Q) x 100
Steps of back titrations
- Work out the moles of titre (T)
- Use T to work out B2
- Calculate Btotal
- Minus B2 from Btotal to find B1
- Use equation to work out moles of A from moles of B1 that reacted with it
