Which statements are correct for the reaction of ethene with bromine the absence of ultraviolet light?
I. It is an addition reaction
II. The organic product is colorless
III. The organic product is saturated
II and III
State the equation for the reaction between methane and bromine to form bromomethane.
CH4 + Br2 --> CH3Br + HBr
Bromine can be produced by electrolysis of molten sodium bromide. Deduce the half-equation for the reaction at each electrode.
- Positive electrode (anode): 2Br- --> Br2 +2e-
- Negative electrode (cathode): Na+ + e- --> Na
State one difference in the physical properties of the isotopes between 63Cu and 65Cu and explain why their chemical properties are the same.
63Cu diffuses at a greater rate than 65Cu
- have the same number of protons and electrons
C5H12 exists as three isomers. Identify the structure of the isomer with the lowest boiling point and explain your choice.
- weakest London dispersion forces because has smallest surface area
Ethanol is a primary alcohol that can be oxidised by acidified potassium dichromate (VI). Distinguish between the reaction conditions needed to produce ethanal and ethanoic acid.
- Ethanal: distill off product as it forms
- Ethanoic acid: use excess oxidising agent
Deduce the half-equation for the oxidation of ethanol to ethanal.
CH3CH2OH --> CH3CHO + 2H+ + 2e-
If a reaction has an exothermic forward reaction, what would happen to the equilibrium constant for the reaction if the temperature were increased?
coordinate (dative) bonds
- the electrons in the shared pair originate from the same atom
- e.g. sulfur dioxide and sulfur trioxide has dative bond between S and O
Which forces are present between molecules of carbon dioxide in the solid state?
temporary dipole-induced dipole interactions
What is the equation for the bond enthalpy of the H-I bond?
HI (g) --> H (g) + I (g)
State an equation for the formation of ethanol from ethene and the necessary reaction conditions.
- CH2CH2 + H2O --> CH3CH2OH
- concentrated sulfuric acid
Bronsted-Lowry vs. Lewish acids and bases
- Bronsted-Lowry: acid is a proton donor, base is a proton acceptor
- Lewis: acid is an electron acceptor, base is an electron donor
Outline how the Mg+ ion is formed in the mass spectrometer. Describe how Mg+ is accelerated in the mass spectrometer.
- collision of Mg atom with high energy electrons
- ion passes through oppositely charged plates
Why in the Haber process is
- a temperature lower than 500C not used?
- a pressure higher than 200atm not used?
- slower rate, uneconomical
- high cost for maintaining plant
Outline an experiment and its results which could be used to distinguish between a strong base and a weak base.
- solutions of equal concentrations of acid and base
- measure pH
- strong base has higher pH
Identify the acid-base character of the oxides of each of the elements from sodium to chlorine in period 3.
Na, Mg oxides - basic
Al oxide - amphoteric
Si-Cl oxides - acidic
Outline two reasons why the polymerisation of alkenes is of economic importance.
- polymers not naturally available
- wide range of uses
when an element can exist in different crystalline forms (e.g. carbon)
Boiling points for organic molecules
- As the carbon chain in a homologous series increases the London dispersion forces of attraction increase so boiling point increases
- when branching occurs the molecules become more spherical in shape so the surface area decreases and the boiling point decreases
what structural feature must a molecule possess in order that it may undergo addition polymerisation?
carbon-carbon double bond
(2C + 2 + N - H - halogens) / 2
primary, secondary, tertiary halogenoalkanes
- primary halogenoalkane: carbon holding halogen is attached to one other thing
- secondary halogenoalkane: carbon holding halogen is attached to two other things
- tertiary halogenoalkane: carbon holding halogen is attached to three other things
what is the pH of acid rain?
less than 5.6
why does the soil become salty in areas where soil is constantly irrigated?
- irrigation waters contain dissolved salts
- salts left behind when water evaporates
describe two ways in soil organic matter contributes to preventing soil degradation
- provides sources of nutrients
- improves structural stability
what is Kc for the reverse reaction?
How are the mass and abundance of an isotope determined in mass spectrometry?
- magnetic field required to deflect isotope onto detector depends on mass of isotope
- signal from detector depends on abundance of isotope
How does the atomic radii of isotopes vary?
- same atomic radii
- isotopes only differ by number of neutrons whereas atomic radius is determined by electron shells and number of protons
is dissolving endothermic or exothermic?
greater the specific heat capacity, ... increase in temperature for a given energy input
evaporation vs. boiling
- evaporation occurs at all temperatures, boiling at bp only
- evaporation occurs at surface, boiling throughout
free radical mechanism diagram