OCR A+Level Chemistry- Module 2
Solutions
What is the oxidation number for combined 02? - ANS--2
Calculate mass number - ANS-(isotope number x abundance)/100
Moles= - ANS-Mass / Mr
Calculating with moles - ANS-1. Balance equation
2. Calculate moles
3. Ratio
4. Calculate the mass, volume, concentration, etc.
Limiting Factor - ANS-The larger amount of moles
Percentage Yield - ANS-actual yield(mol)/theoretical yield(mol) x 100
Atom economy - ANS-(Molecular mass of desired products/ Molecular mass of all
products) x 100
Gas calculations - ANS-mol=vol(dm3)/24
Concentration= - ANS-moles/volume
Ideal gas equation - ANS-PV=nRT
Calculating empirical formula - ANS-Pretend that you have a 100g sample.
That is, change % to grams.
Convert the grams to moles for each element.
Divide each number by the smallest number.
Multiply the result(if needed) to get rid of any fractions.
Calculating water of crystallisation - ANS-mass of hydrated- mass of sulfate= mass of
water
, find moles of sulphate and water
ratio the moles
What is an isotope? - ANS-atoms of the same element with the same number of protons
but different number of neutrons
Atomic Structure - ANS-Electron on outer shell, neutron and proton in center, nuclei.
Relative isotopic mass - ANS-The mass of an atom of an isotope compared with
one-twelfth of the mass of an atom of carbon-12.
Relative atomic mass - ANS-The weighted mean mass of an atom of an element
compared with one-twelfth of the mass of an atom of carbon-12.
Mole - ANS-the SI base unit used to measure the amount of a substance
Avogardos constant - ANS-6.02 x 10^23 particles
Empirical formula - ANS-the simplest whole number ratio of atoms of each element
present in a compound
molecular formula - ANS-The number and type of atoms in each element of a molecule
Anhydrous - ANS-without water
Hydrated - ANS-with water
Water of crystallisation - ANS-Water molecules that form an essential part of the
crystalline structure of a compound
Strong acid - ANS-an acid that ionizes completely in aqueous solution Strong
base - ANS-A base that dissociates completely into ions in solution. Weak acid -
ANS-an acid that is only slightly ionized in aqueous solution Weak base - ANS-A
base that does not dissociate completely into ions in solution. Alkali - ANS-A base
that dissolves in water
Solutions
What is the oxidation number for combined 02? - ANS--2
Calculate mass number - ANS-(isotope number x abundance)/100
Moles= - ANS-Mass / Mr
Calculating with moles - ANS-1. Balance equation
2. Calculate moles
3. Ratio
4. Calculate the mass, volume, concentration, etc.
Limiting Factor - ANS-The larger amount of moles
Percentage Yield - ANS-actual yield(mol)/theoretical yield(mol) x 100
Atom economy - ANS-(Molecular mass of desired products/ Molecular mass of all
products) x 100
Gas calculations - ANS-mol=vol(dm3)/24
Concentration= - ANS-moles/volume
Ideal gas equation - ANS-PV=nRT
Calculating empirical formula - ANS-Pretend that you have a 100g sample.
That is, change % to grams.
Convert the grams to moles for each element.
Divide each number by the smallest number.
Multiply the result(if needed) to get rid of any fractions.
Calculating water of crystallisation - ANS-mass of hydrated- mass of sulfate= mass of
water
, find moles of sulphate and water
ratio the moles
What is an isotope? - ANS-atoms of the same element with the same number of protons
but different number of neutrons
Atomic Structure - ANS-Electron on outer shell, neutron and proton in center, nuclei.
Relative isotopic mass - ANS-The mass of an atom of an isotope compared with
one-twelfth of the mass of an atom of carbon-12.
Relative atomic mass - ANS-The weighted mean mass of an atom of an element
compared with one-twelfth of the mass of an atom of carbon-12.
Mole - ANS-the SI base unit used to measure the amount of a substance
Avogardos constant - ANS-6.02 x 10^23 particles
Empirical formula - ANS-the simplest whole number ratio of atoms of each element
present in a compound
molecular formula - ANS-The number and type of atoms in each element of a molecule
Anhydrous - ANS-without water
Hydrated - ANS-with water
Water of crystallisation - ANS-Water molecules that form an essential part of the
crystalline structure of a compound
Strong acid - ANS-an acid that ionizes completely in aqueous solution Strong
base - ANS-A base that dissociates completely into ions in solution. Weak acid -
ANS-an acid that is only slightly ionized in aqueous solution Weak base - ANS-A
base that does not dissociate completely into ions in solution. Alkali - ANS-A base
that dissolves in water
