Chemistry Module 2 Flashcards
What is an isotope?
Atoms with the same number of protons and different number of neutrons
why do isotopes have the same chemical properties?
Isotopes have the same configuration of electrons
Explain why isotopes can have different physical properties
Physical properties depend on the mass of the atom
What is relative atomic mass?
The weighted mean mass of an atom of an element compared to 1/12 of the mass of a carbon 12 atom
What is relative isotopic mass?
The weighted mean mass of an isotope compared with 1/12 the mass of a carbon 12 atom
What is relative molecular mass
The average mass of a molecule compared to 1/12 of the mass of a carbon 12 atom
What is relative formula mass?
The average mass of a formula unit compared to 1/12 the mass of a carbon 12 atom
How to calculate relative molecular mass
Amount of atom of one element + atomic mass x amount of other atoms of the element + atomic mass
How to calculate relative formula mass
product of the amount of atoms of the elements
Explain the term amount of substance
Number of particles measured using a unit called the mole (n)
What formula finds the number of moles from the number of atoms or molecules?
Number of moles = Number of particles you have
Number of particles in a mole
What is molar mass?
The mass per mole of a substance (gmol-1)
What is the formula that finds number of moles from the molar mass?
Number of moles = mass of substance
molar mass
What is molar gas volume?
The gas volume per mole (dm3mol-1)
What are two formulas that finds the number of moles in a volume of gas?
Number of moles = volume of dm3/cm3
24/24000
What is the ideal gas equation?
pV = nRT pressure(Pa) x volume(m3) =
moles x temperature(K) x the gas constant(JK-1mol-1)
What is the procedure required to measure gas volumes?
Connect the gas syringe to the container to collect all gas produced by a reaction.
As the gas is produced the plunger is pushes out the syringe and the volume of gas collected can be read
What are the techniques required to measure gas volumes?
.
What is the formula that finds the number of moles from concentration and volume?
Number of moles = Concentration x volume in cm3/dm3
1000/1
What does the empirical formula tell you?
The simplest whole number ratio of atoms of each element present in a compound
What does the molecular formula tell you?
The actual number and type of atoms of each element in a molecule
What is the formula for nitrate?
NO3-
What is the formula for carbonate?
CO32-
What is the formula for sulfate?
SO42-
What is the formula for ammonium?
NH4+
What is an acid?
A proton donor which releases H+ ions in aqueous solution
What is a base?
A proton acceptor which releases OH- ions in aqueous solution
What is the formula of sulfuric acid?
H2SO4
What is the formula for nitric acid?
HNO3
What is the formula for ethanoic acid?
CH3COOH
what is the formula for ammonia?
NH3
Explain a strong acid?
The acid fully ionizes in solution and releases and lots of H+ ions
Explain a weak acid?
Only a small amount of the acid ionizes and releases a little amount of H+ ions
What is a neutralisation reaction?
The reaction where H+ and OH- ions form H2O
What does an acid-base reaction produce?
Salt + water
What does an acid-metal reaction produce?
Salt + hydrogen
What does an acid-metal oxide reaction produce?
Salt + water
What does an acid-metal hydroxide reaction produce?
Salt + water
What does an acid-metal carbonate reaction produce?
Salt + carbon dioxide + water
What does anhydrous salt mean?
The salt doesn’t contain water of crystallization
What does hydrated salt mean?
A salt containing water of crystallization
What does water of crystallization mean?
The water in a lattice
How to calculate the formula of a hydrated salt?
. Find the mass of water lost (mass of hydrated salt - mass of anhydrous salt)
. Find the number of moles of water lost
. Find the number of moles of anhydrous salt produced
. Work out the ratio of moles of anhydrous salt to moles of water
What is a titration?
Titrations allow you to find out exactly how much acid is needed to neutralise a quantity of alkali
How to perform an acid-base titration
. Measure out some alkali using a pipette and put it in a flask with a few drops of indicator (phenolphthalein)
. Take an initial reading to see how much acid is in the burette to start off with
. Add the acid to the alkali swirling the flask continuously
. Stop when the indicator shows a permanent colour change (colourless)
. Record the final reading from the burette
How to calculate concentration using a titration
. Work out moles (conc x col in cm3 ./. 1000)
. work out conc (moles x 1000 ./. vol in cm3)
How to calculate the volume using a titration
. Work out moles (conc x vol in cm3 ./. 1000)
. work out vol ( moles x 1000 ./. conc)
What is meant by theoretical yield?
The mass of product that should be formed in a chemical reaction
How to calculate theoretical yield
. work out moles of the limiting reactant
. work out the moles of product that the reactant should make
. calculate the mass of that many moles of product
What is meant by percentage yield?
The actual amount of product you collect
What formula finds percentage yield?
Percentage yield = Actual yield
Theoretical yield x100
What is meant by atom economy?
a measure of the proportion of reactant atoms that become part of the desired product
How to calculate atom economy
. Find the molar mass of the desired product
. Find the molar mass of the products
. Use the equation (mr of desired product
sum of molar mass of all products x100
Why are reactions with low atom economy not used in industry?
. there’s lots of waste produced
. expensive to dispose of waste products safely
. less sustainable
What are the rules for assigning oxidation numbers
- uncombined elements = 0
- simple monatomic ion = same as its charge
- each atom in molecular ions = sum of there oxidation numbers
- Neutral compound (2cl- mg2+) = 0
- oxygen = -2 except in peorxides (O22-) = -1
- Hydrogen = +1 except in metal hydrides (MHx) = -1
what does the oxidation number tell you?
the total number of electrons it has donated or accepted to form an ion or part of a compound
What is a redox reaction?
Reduction and oxidation happen simultaneously
What is oxidation?
loss of electrons
What is reduction?
gain of electrons
what is the role of an oxidising agent?
accepts electrons from another reactant and is reduced
What is the role of a reducing agent?
donated electrons to another reactant and is oxidised
How many orbitals make up the s subshell?
1
How many orbitals make up the p subshell?
3
How many orbitals make up the d subshell?
5
How many electrons can fill up the s subshell?
2
How many electrons can fill up the p subshell?
6
How many electrons can fill up the d subshell?
10
How many electrons can fill the first four shells?
2,8,18,32
what are atomic orbitals?
A region around the nucleus that can hold up two two electrons with opposite spins
What is meant by electron configuration?
The number of electrons that an atom or ion has and how they are arranged in different ways
what is the shape of the s and p subshells?
spherical and dumbell
What is an electron spin?
the momentum that an electron has
Describe ionic bonding
The electrostatic attraction between positive and negative ions
what causes the structure of a giant ionic lattice?
when oppositely charged ions from an ionic bond
Explain what an ionic lattice is?
The same basic unit repeated formed because each ion electrostatically attracted in all directions to ions of opposite charges.
what are the physical properties of ionic compounds?
. conducts electricity when molten or dissolved - the ions are free to move and carry charge
. high melting and boiling point - held together by strong electrostatic forces that need lots of energy to overcome
. soluble in water - water molecules are polar and part of the molecule has a small negative charge and positive charge so water molecules pull the ions away from the lattice and cause it to dissolve
Define covalent bond
Strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
What happens in a dative covalent bond
one of the atoms provides both of the shared electrons
What is average bond enthalpy?
measures the energy required to break a covalent bond
what is the electron shell repulsion theory?
The theory that in a molecule lone pair- lone pair bond angles are the biggest, lone pair-bonding pair are the second and bonding pair-bonding pair are the smallest because lone pairs repel more
what shape name is a atom with three electron pairs?
Trigonal planar(BF3)- the repulsion of the bonded pairs are equal and form a bond angle of 120.
what shape name is a atom with two electron pairs?
Linear(BeCl)- the bonded pairs repel the same and are as far away from each other creating a bond angle of 180.
what shape name is a atom with two electron pairs and one lone pair?
Non-linear - The lone pair repels more than the bonding pairs and creates a bond angle of less than 120.
what shape name is a atom with three electron pairs and one lone pair?
Trigonal pyramidal(NH3)- There is a larger bond angle between the lone pairs than the bonding pairs creating a bond angle of 107.
what shape name is a atom with four electron pairs?
Tetrahedral(CH4) - The charge clouds all repel equally creating a bond angle of 109.5
what shape name is given to an atom with two electron pairs and two bonding pairs?
Bent(H2O)- the lone pair-lone pair repulsion makes the bond angle smaller and creates a bond angle of 104.5.
what shape name is given to an atom with five bonding pairs?
Trigonal bipyramidal(PCl5)- repulsion between the bonding pairs means three will form a trigonal planar with bond angle 120. and the other two atoms will be 90. to them
what shape name is given to an atom with six bonding pairs?
Octahedral(SF3)- all of the bond angles in the molecule are 90.
Define electronegativity
the ability of an atom to attract the bonding electrons in a covalent bond
How to use Pauling electronegativity values to predict the type of bond that will form between atoms
electronegativity is measured on the pauling scale- a higher number means an element is better able to attract the bonding electrons
What is the trend in electronegativity
Electronegativity increases across periods and decreases down groups so fluorine is the most electronegative element
why do polar bonds have permanent dipole dipoles
The covalently bonded atoms have different electronegativities causing a permanent dipole
what is a dipole?
the difference in charge between the two atoms caused by a shift in electron density in the bond
what are permanent dipole dipole interactions?
delta positive and delta negative charges on polar molecules cause weak electrostatic forces of attraction between molecules
what are intermolecular forces?
forces between molecules depending on the induced and permanent dipole-dipole interactions
what are induced dipole-dipole interactions
a weak attraction caused when there is a disruption in the arrangement of electrons in a non-polar molecule
what is the structure of a simple molecular lattice?
covalently bonded molecules attracted by intermolecular forces
what is hydrogen bonding
intermolecular bonding between molecules containing N,O or F and the H atom of -NH, -OH or HF
What are the anomalous properties of H2O resulting from hydrogen bonding?
.High melting point
. Low density
what are the physical properties of simple covalent compounds?
. can’t conduct electricity- covalent molecules are uncharged
. low melting and boiling point- the intermolecular forces are weak and don’t need much energy to break
. insoluble - covalent molecules are non-polar
