Ocr-A Chemistry

• All organic chemicals are covalent molecules based on the element carbon.
• Methanol, ethanol, and propanol are examples of alcohols.
• The lines in the displayed formula of organic molecules represent covalent bonds.
• Carbon atoms can form four covalent bonds, hydrogen atoms form one covalent bond, and oxygen atoms form two covalent bonds.
• Organic molecules have two parts: a chain of carbon atoms bonded to hydrogen atoms, referred to as the hydrocarbon chain, and a second part which is an oxygen atom covalently bonded to a hydrogen atom, referred to as the alcohol group.
• All organic molecules react in a similar way because they all contain the alcohol group, referred to as the functional group.
• A homologous series of organic molecules have the same functional group but each successive member has an additional CH2.
• All the members of a homologous series have the same functional group.
• Each member of a homologous series has an additional CH2.
• Branch chain hydrocarbons have a side chain or branch.
• The prefix in the name of a branch chain hydrocarbon tells us the number of carbon atoms in the main chain.
• In the case of alkenes, the number following the prefix shows the position of the double bond, and we start from the end of the molecule which produces the lowest numbers.
• The longest chain of carbon atoms in a branch chain hydrocarbon is always identified first.
• The number of carbon atoms in the side chain of a branch chain hydrocarbon is determined by the prefix, for example, a one carbon side chain is called a methyl group.
• The position of the methyl group on the main carbon chain of a branch chain hydrocarbon is stated by numbering from the side with the least carbons.
• A two carbon side chain in a branch chain hydrocarbon is called an ethyl group.
• The name of a branch chain hydrocarbon is based on the longest chain and the side chains are listed alphabetically with the lowest possible numbers.
• In a branched alkene, the longest chain has five carbon atoms and the double bond lies between carbons two and three, so this is based on the molecule pent-two ene.
• The electrophilic addition of a halogen molecule to an alkene involves the pair of electrons in the double bond of the alkene being attracted to the positive hydrogen atom of the hydrogen bromide, forming a covalent bond.
• The product of the first stage of the reaction is a carbocation intermediate with a positive charge on a carbon atom and a bromide ion.
• In the second stage of the reaction, the electron pair on the bromide ion are attracted to the positive carbon atom in the carbocation intermediate, forming a covalent bond and resulting in the product.
• The reaction between an alkene and a halogen molecule involves the halogen molecule adding across the double bond, resulting in the two halogen atoms ending up on two adjacent carbon atoms.
• Hydrogen halide molecules have a permanent dipole, whereas in halogen molecules the dipole is induced.
• When a hydrogen halide is added to an asymmetric alkene, two products are made, a major and a minor product.
• When a halogen is added to an asymmetric alkene, only one product is made.
• Bromine water, which has an orange brown colour, is used to test for the presence of an unsaturated molecule such as an alkene.
• If a substance is unsaturated, the bromine in bromine water will add across a double bond and the product of the reaction will be colorless, causing the orange bromine water to decolorize.
• If a substance is saturated, the bromine in bromine water will not react and the bromine water will remain orange.
• The relative atomic mass is the weighted mean mass of an atom of an element relative to carbon-12
• The relative isotopic mass is the mass of an isotope relative to carbon-12
• Mass spectrometer

  • A sample is vaporised and then ionised, this forms positive ions
  • The ions are accelerated
  • Heavier ions=slower movement
  • lighter ions= faster movement
  • Isotopes are separated based on mass
  • The greater abundance of ions that reach the detector = larger signal
  • This is shown on the mass spectrum as a mass to charge ratio
• Ammonium, NH4 has a positive charge and is a weak base
• Nitrate has an overall charge of -1 and is a strong base, NO3-
• Nitrite has an overall -1 charge and is a reducing agent. NO2-
• Hydrogen carbonate is HCO3- . It is a weak base
• Carbonate has an overall charge of 2- , CO3 2- .
• Sulphite has an overall charge of 2-, SO3 2-.
• Dichromate(VI) has an overall charge of 2- , Cr2O7 2-
• Phosphate has an overall charge of 3, PO4 3-
• $n=$$m/M$The amount/ number of moles is equal to the mass,m, over the molar mass, M. MOlar mass is found using the periodic table.