AQA AS Organic Chemistry exam questions with 100% correct answers

AQA AS Organic Chemistry exam questions with 100% correct answers Define the term 'empirical formula' - ANSWERS A formula that gives the simplist whole number ration of atoms of each element in a compound Define the term 'molecular formula' - ANSWERS A way of representing molecules that shows the actual number of atoms of each element in a molecule Define the term 'General formula' - ANSWERS An algebraic formula that can describe any member of a family of compounds Define the term 'Structural formula' - ANSWERS A way of representing molecules that shows the atoms carbon by carbon, with the attached hydrogens and functional groups Define the term 'Displayed formula' - ANSWERS A way of representing a molecule that shows every atom and every bond Define the term 'Skeletal formula' - ANSWERS A simplified organic formula which only shows the carbon skeleton and associated functional groups How do you draw structures in 3D? - ANSWERS Wedges - Bonds coming out of the paper Dotted lines - Bonds going into the paper Normal lines - Bonds in the plane of the paper Define the term 'Homologous series' - ANSWERS A family of organic compounds that have the same general formula and similar chemical properties Define the term 'Structural isomer' - ANSWERS A molecule with the same molecular formula as, but different structural formula to another molecule Define the term 'Stereoisomerism' - ANSWERS A molecule which has the same structural formula as another molecule, but has its atoms arranged differently in space Define the term 'E-isomer' - ANSWERS A stereoisomer of an alkene that had the two highest priority groups on opposite sides of the carbon-carbon double bond Define the term 'Z-isomer' - ANSWERS A stereoisomer of an alkene that has the two highest priority groups on the same side of the carbon-carbon double bond (To help you remember it: Zee Zame Zide). Define the term 'E/Z isomerism' - ANSWERS A type of stereoisomerism that is cause ld by the restricted rotation about a carbon-carbon double bond, each of he carbon atoms must have two different groups attached Define the term 'Alkanes' - ANSWERS A saturated hydrocarbon with the general formula CnH2n+2 Define the term 'Petroleum' - ANSWERS A mixture consisting mainly of alkane hydrocarbons that can be separated into different fractions Define the term 'Cracking' - ANSWERS Long chain hydrocarbons are broken down into shorter chain hydrocarbons. This produces a mixture of alkanes and alkenes Describe thermal cracking. Include conditions in your answer. - ANSWERS Temperatures between 700k and 1200k Pressure of up to 7000 KPa. 1) Carbon-carbon breaks to produce two free radicals. 2) Free radicals are highly reactive and react to produce many alkenes and some alkanes. Why are long chain hydrocarbons not kept under high temperatures for long amounts of time? - ANSWERS At higher temperatures, these chains decompose. Given enough time, this will eventually result in products which are only hydrogen gas and solid carbon. Describe catalytic cracking. Include conditions in your answer. - ANSWERS Zeolite catalyst. 720K. Low pressure. Hydrocarbons are mixed with a catalyst which has been ground into a fine powder. Produces lots of branched alkanes and aromatic hydrocarbons Describe a zeolite catalyst - ANSWERS A substance which has a honeycomb structure with an enormous surface area. They are usually acidic. What type of products are usually formed from catalytic cracking? - ANSWERS Branched alkanes Cycloalkanes (rings) Aromatic compounds (e.g. benzene) Define the term 'Halogenoalkanes' - ANSWERS An alkane with at least one halogen atom in place of a hydrogen atom Define the term 'Ozone layer' - ANSWERS A layer of ozone (O3) found in the earth's upper atmosphere which protects the earth from ultra violet radiation Define the term 'Alkenes' - ANSWERS An unsaturated hydrocarbon with the general formula CnH2n, containing at least one carbon-carbon double bond How can we test for the presence of a C=C double bond? - ANSWERS Add bromine water (an orange solution) to the unknown solution. If a C=C double bond is present then the solution will decolourise (turn colourless). What conditions are needed for an alcohol to be made from an alkene? - ANSWERS Steam High temperature