[ chem module 2 key definitions ] Flashcards
What is the atomic number?
The number of protons an element has.
What is an isotope of an element?
An isotope of an element will have the same number of protons and electrons but a different number of neutrons.
What is an ion?
An ion is a charged atom which either lost or gained electrons.
What is the difference between a cation and anion?
Cation is a positive ion which lost electrons.
Anion is a negative ion which gained electrons.
[Try remember anion as an onion which is bad boo hoo therefore negative]
What is the relative isotopic mass?
The mass of an isotope relative to 1/12th the mass of a carbon-12 atom.
What is the definition of relative atomic mass?
The weighted mean mass of an atom of an element relative to 1/12th the mass of a carbon-12 atom.
How do you calculate the relative atomic mass?
Contribution from isotope x percentage / 100
For example, (75.78x35) + (24.22x37) / 100
What is the formulae for an ammonium ion?
NH4+
What is the formulae for a hydroxide ion?
OH-
What is the formulae for a nitrate ion?
NO3-
What is the formulae for a carbonate ion?
CO3 2-
What is the formulae for a sulfate ion?
SO4 2-
Example question: What is the formulae for zinc chloride?
ZnCl2
Example question: What is the formulae for aluminium sulfate?
Al2(SO4)3
What is the avogadro constant?
The number of particles in each mole of carbon-12 atom.
6.02x 10^23
What are the three mol equations?
Mol: Mass/Mr
Mol: Conc x Vol (dm3)
Mol: Vol/24 (for gases)
What is the molecular formulae?
The number of atoms of each element in a molecule.
What is the empirical formulae?
The simplest whole number ratio of atoms of each element in a compound.
Example question: What is the empirical formulae for C6H12O6
CH2O
How do you calculate empirical formulae?
1) Do mass/mol or percentage/mr
2) Find the simplest whole number ratio and divide the smallest whole number
Example question: Chemical analysis of a compound gave composition by mass C: 40% H: 6.67% O: 53.33%
C6H12O6
[Ask me if u don’t understand why hehe]
What are the water of crystallisation?
The water molecules that are part of a crystalline structure.
What does it mean when a Crystal is hydrated?
It contains water molecules.
What does it mean when a crystal is anhydrous?
Water molecules are absent.
Why do you assume during water of crystallisation experiments?
+All of the water has been lost
+There is no further decomposition
What is the ideal gas equation? What does each letter represent and what unit is used?
pV= nRT
p: pressure (Pa) V: volume (m3) n: mol R: ideal gas constant (8.31 jmol-1K-1) T: temperature (K which is degrees +273)
What is the equation for percentage yield?
Percentage yield= Actual yield/Theoretical yield x 100
What is atom economy?
The sum of molar masses of desired products/ The molar masses of all products x 100
What is the difference between a strong and weak acid?
A strong acid like HCL will completely dissociate (release all H+ ions) wheres a weak acid like CH3COOH will only partially dissociate (release some H+ ions)
What is an alakli?
A base that will dissolve in an aqueous solution and release OH- ions
What is a salt?
A chemical compound formed when the H+ atom is replaced by a metal. For example sodium chloride (NaCl)
What is an acid?
A substance when dissolved in H2O will release hydrogen ions (H+)
What is formed when an acid reacts with a metal oxide/hydroxide?
Acid + Metal Oxide/Hydroxide -> Salt + Water
Example Question: What is formed when Copper oxide reacts with sulfuric acid? Write both the word and symbol equation with state symbols.
Word: Copper oxide + Sulfuric acid -> Copper Sulphate and Water
Symbol: CuO (s) + H2SO4 (aq) -> CuSO4 (aq) + H2O (l)
What is formed when acids react with carbonates?
Acid + Carbonate -> Salt + Water + Carbon Dioxide
What is an oxidation number?
The number of electrons involved in bonding.
What is a standard solution in titrations?
A solution with a known concentration.
