Flashcards in Module 2.1 Deck (48):
Relative isotopic mass
The mass of an atom of an isotope compared with one twelfth of the mass of an atom of carbon 12
Relative isotopic mass (Ar)
The weighted mean mass of an atom of an element compared with one twelfth of the mass of an atom of carbon 12
What is a mass spectrometer used for
- identify an unknown compound.
- find the relative abundance of each isotope of an element.
- determine structural information about molecules.
How does a mass spectrometer determine the mass of a molecule or isotope?
By measuring the mass to charge ratio of ions by causing substances to become positive ions. The positive ions are then passed through the apparatus and separated according to their mass and charge. A computer analyses the data on the ions present and produces a mass spectrum.
Which atoms do not normally from ions and why?
Be, B, C and Si
Because they require to much energy to transfer the outer shell electrons to form ions.
Give the names and formulae of 1+, 1- and 2- molecular ions.
1+ : ammonium NH4 +
1- : hydroxide OH -
Nitrate NO3 -
2- : carbonate CO3 2-
Sulfate SO4 2-
the amount of any substance containing as many particles as there are carbon atoms in 12g of the carbon 12 isotope.
Avogadro constant (Na)
The number of atoms per mole of the carbon 12 isotope.
(6.02 * 10^23)
Molar mass (M)
The mass per mole of a substance (g mol^-1)
Which type of compounds are molecular formulae used for?
What was Avogadros hypothesis
Under the same conditions of temperature and pressure, a mole of any gas would fill the same volume of space.
Why is avogadros law now important
It means that we can compare the number of molecules in different gases by comparing their volumes.
What if the volume per mole of gas molecules at room temperature and pressure?
24.0 dm^3 mol^-1
Molar gas volume
The volume per mole of gas. ( 24.0 dm^3 mol^-1)
Do all gases have the same mass or volume?
Same volume but different masses
Do gases experience any intermolecular forces?
What is the concentration of a solution?
The amount of solute in mol dissolved per 1dm3 of solution.
A solution of known concentration
What are standard solutions used for?
They are used in titrations to determine unknown information about another substance.
disadvantages of disposing off by products
It's costly poses potential environmental problems wastes valuable resources
What does atom economy consider?
the by products of a chemical reaction as well as the desired product
What does a percentage yield tell you?
the efficiency with which reactant are covered into products
what does the atom economy tell you?
the proportion of desired products compared with all the products formed
what happens if u use a process with a higher atom economy
less waste is produced
How does the type of reaction effect atom economy?
addition reactions have an atom economy of 100% Whereas substitution and elimination reactions have an atom economy of less than 100%
what do elimination, addition and substitution reactions involve?
Elimination reactions involve the removal of a small molecule from another molecule.
Addition reactions involve two or more reactants joining together.
Substitution reactions involve one atom or molecule swapping places with another.
Give the formulae of common acids
CH3COOH (ethanoic acid)
What happens when an acid is added to water ?
The acid releases H+ ions into solution
What type of acids are good at giving away H+ ions and what type are good at accepting them back?
Strong acids are good at giving up H+ ions and bad at accepting them back. Whereas weak acids are not good at giving them away but are good at accepting H+ ions back
Give examples of bases
Metal oxides: Mpg/ Cup
Metal hydroxides: NaOH /Mg(OH)2
A chemical that is a proton donor and releases H+ (aq) in solution
A chemical that reacts with an acid and is soluble in water releasing OH- (aq) ions
A chemical that can react with acids and is a proton acceptor
Why is ammonia able to react with acids?
When dissolved in water ammonia forms a weak alkaline solution
Give the formulae of common alkalines
Equation- ammonia reacts with water to form a weak base
NH3 (aq) + H2O = NH4+ (aq) + OH- (aq)
(= - equilibrium sign)
Substances that can react as acids and bases. Eg- glycine
what happens if one H+ ion is replaced in sulfuric acid
an acid salt is formed
How are salts produced?
by neutralizing acids with bases
what is the ionic equation for neutralisation?
H+ (aq) + OH- (aq) 》H2O (l)
what are the products when an acid is reacted with a base? (carbonate/ metal oxide/ alkali/ metal)
acid + carbonate 》salt + carbon dioxide + water acid + metal oxide 》 salt + water acid + alkali 》 salt + water Acid + metal 》 salt + hydrogen
A crystalline compound containing water molecules
A substance that contains no water molecules
water of crystallisation
water molecules that form an essential part of the crystalline structure of a compound
what information does the dot formula give?
it gives the ratio between the number of compound molecules and the number of water molecules within the crystalline structure
Why do chemists use oxidation numbers
to keep track of how electrons are being used in bonding
How do you find out the oxidation number of different compounds of transition elements
their Roman numerals show their oxidation states