General Flashcards
How do van deer waals forces arise?
- uneven distribution of electrons
- creates instantaneous dipole
- causes an induced dipole on neighbouring molecule
Define molecular formula
Actual number of atoms of each element present in a molecule
How can you tell a salt has been formed?
Hydrogen ion replaced by metal ion
Define ionic lattice
Repeating pattern of oppositely charged ions
Define electronegativity
Ability of atom to attract electrons in a covalent bond
What is a base
Substance that readily accepts H+ ions
What is an alkali
Substance that releases OH- ions into solution
How are catalysts good for environment
Lower temp can be used - reduces co2 emissions
Reduces use of toxic reactants
Define enthalpy change
When one mole of bonds is broken
What makes a molecule polar
Not symmetrical so dipoles don’t cancel out
Difference in electronegativities
State hess’ law
The enthalpy change of a reaction is independent to the route it takes
Define standard molar enthalpy of formation
The energy change when one mole of compound is formed from is constituent elements in standard state
What do m and z stand for
Mass
Charge
What is the chemical name for bicarbonate of soda?
Sodium hydrogen carbonate
What is a heterogeneous equilibrium?
Reactants in a different state
Why is boiling point of PH3 lower than boiling point of AsH3?
AsH3 has more electrons
Stronger induced dipole-dipole interactions
What are the stages of reducing a haloalkane to primary amine?
Haloalkane
Nitrile
Primary amine
What does Hess’ law state?
The enthalpy change accompanying a chemical change is independent of the route by which the chemical change occurs
What is a dynamic equilibrium?
Rate of fowards reaction equals the rate of backwards reaction
What does aromatic mean?
The compound contains a benzene ring
What are the three types of structural isomer?
Chain, positional, functional group
What is a sigma bond?
A single covelant bond made up of two shared electrons with the electron density concentrated between the two nuclei
What is a pi bond?
Formed by the side ways overlap of two p orbitals on adjacent carbon atoms, each one providing one electron
What is a radical?
A particle with an unpaired electron
Why are alkenes unreactive?
The C-H bonds have very low polarity
C-H bonds are relitavley strong
What determines highest priority in E/Z isomerism
Atomic number
Reaction conditions for Hydration of ethene
Water with phosphoric acid at 300 degrees with high pressure
Conditions to dehydrate an alcohol
Conc sulfuric acid and Al2O3
What does the dehydration of an alcohol give?
An alkene
Conditions to hydrolyse a haloalkane
the solvent must be in water and must be heated under refulx
How can you rest the trend in rates of reaction in haloalkanes?
Mix with water and silver nitrate
Heat
Monitor the rate at which precipitate forms.
What affects ionisation energy?
Atomic radius
Nuclear charge
Shielding effect
What is the most reactive halogen?
Fluorine
Fluorine oxidises water to give what>
HF and O2
What colour is iodine in cyclohexane?
Purple
What colour is bromine in cyclohexane?
Orange
What colour is chlorine in cyclohexane?
pale yellow
Equation for pka
-logKA
Equation for KA
10-pka
How can you distinguish between stereo isomers?
Plane polarised light rotated equally in opposite directions
How do you convert gdm-3 into mol dm-3
gdm-3 divided by mr
How do van der waals forces arise?
Unequal distribution of electrons
causes instantaneous dipole
Causes induced dipole on neighbouring molecules
What are some issues of making chiral drugs?
Enantimors could be toxic
Have to seperate 1:1 ratio of enantimors
How does GC-MS allow products to be identified?
Seperates compounds and comparison with a data base
What is the chemical responsible for the peak at 0 in NMR and why is it added?
TMS
Standard for chemical shift measurement
Show how ALCl3 behaves as a catalyst
AlCL3 + Cl2 –> AlCl4- + Cl+
H+ + AlCl4- —-> AlCl3 + HCl
Reagents needed for reduction og 1,4-dinitrobenzene
Tin and conc HCl
Define the term lattice enthalpy
The energy change that takes place when one mole of ionic compound is formed from its constituent ions in gaseous state
Explain why it is difficult to predict whether the lattice enthalpy of magnesium bromide would be more or less exothermic than the lattice enthalpy of sodium chloride
Mg has a greater charge and therefore greater charge density than sodium
Bromine has smaller atomic radius
However not paired with eachother
Would the entropy change of magesium with dilute sulfuric acid be positive or negative?
Positive as a gas is formed which is more disordered
Would the entropy change of the complete combustion of ethane be positive or negative?
Negative
9 mol of gas to 4 mol of gas so less disordered
How can a sutible indicator be chosen from looking at a pH titration curve graph?
Chose the indicator that changes in the vertical section
Steps to purify 2-hydroxybenzoic acid
Dissolve in the minimum amount of hot solvent Cool in ice bath forming crystals Vacuum filtration using buchner flask Rinse with cold solvent Dry in oven
Why does bromine have a higher boiling point than chlorine?
Bromine has more induced dipole interactions
Why does water expand when it is frozen?
H bonds in ice hold H2O molecules further apart
Why does the production of chloromethane by radical substitution produced a very low percentage yield?
further substitution occurs
Why are C-C bonds all the same in benzene?
Pi bonds are delocalised
How can IR distinguish between ketones and carboxylic acids?
Carboxylic acids have a broad O–H absorption at 2500–3300
Why is the rate of hydrolysis of 1-bromobutane is faster than that of 1-chlorobutane.
C-Br bond is weaker
Units for ideal gas equation
T in K
V in m3
p in Pa
