Name:_________________________________ Chemistry Post-Enrolment Worksheet The purpose of this worksheet is to get you to recap some of the fundamental concepts that you studied at GCSE in preparation for your first topic of study at A-level. Please complete the worksheet and bring it in for your first chemistry lesson. If you need help answering any of these questions, you can use the links provided in each section. You will find a copy of the periodic table on the back page that you can use to help you answer the questions. Section 1 – The Mole The molar mass of a substance is the mass (in g) of one mole of a substance. For Example 12g of Carbon contains one mole of C atoms  18g of water contains 1 mole of water molecules Carbon 12.0 C 6 1) How many moles of the following are there? a) 32g of sulfur atoms c) 132g of CO2 molecules b) 20g of calcium atoms d) 3.16kg of KMnO4 (1kg = 1000g) (4 marks) This helps us to understand the equation that links number of moles with mass – the equation you will have been taught at school is: The mole is in fact just a counting tool. In the same way that a couple = 2 and a dozen = 12, one mole of any substance = 6.02 x 1023 particles of that substance. E.g., 5 moles of sodium will contain 5 x 6.02 x 1023 individual sodium atoms. 2) Calculate the number of atoms in the following: a) 2 moles of carbon atoms c) 8g of sulfur atoms b) 0.5 moles of mercury atoms d) 3kg of magnesium atoms (4 marks) For help with this section, try the following link; http://www.chem1.com/acad/webtext/intro/int-2.html Section 2 – Percentage Mass Calculations When dealing with compounds we can calculate the percentage by mass of each element that it contains. For example, carbon dioxide contains carbon and oxygen: 12/44 x 100 = 27% Carbon (2 x 16) / 44 x 100 = 73% Oxygen 3) Calculate the percentage mass of; a) magnesium in magnesium oxide c) nitrogen in NH4NO3 b) lithium in lithium oxide d) copper in Cu2(OH)2CO3 (4 marks) For help with this section, try the following link; http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/chemcalc/chemcalc_bot hrev5.shtml Section 3 – Balancing Chemical Equations To represent a chemical reaction we could write a word or symbol equation. At A level, you will be expected to interpret, construct and balance symbol equations. CH4 + 2O2 CO2 + 2H2O In order to balance an equation you must make sure the number and type of each atom is the same on both sides of the equation – this is not always as easy as it sounds! 4) Write out balanced symbol equations for the following reactions: a) lithium + water → lithium hydroxide (LiOH) + hydrogen (H2) b) nitrogen (N2) + hydrogen → ammonia (NH3) c) ethane (C2H6) + oxygen (O2) → carbon dioxide + water d) ethanol (C2H5OH) + ethanoic acid (CH3COOH) → ethyl ethanoate (C2H5OOCCH3) + water (12 marks) For help with this section, try the following link; http://www.ausetute.com.au/balcheme.html Section 4 – Writing the Formulae for Ionic Compounds In simple terms, ionic compounds are those which contain a metal and a non-metal. The overall charge of an ionic compound is zero, therefore the charges of the ions that make up the compound must add up to zero. e.g. sodium chloride is made up of Na+ ions and Cl- ions. The overall formula is NaCl lithium oxide is made up of Li+ ions and O2- ions. The overall formula is Li2O Polyatomic ions are those that contain more than one atom e.g. the hydroxide ion (OH-), which is made up of an oxygen atom and a hydrogen atom and has an overall 1- charge. Brackets can be used if we need more than one of a polyatomic ion in our formula. e.g. ammonium carbonate is made up of ammonium ions, NH4+ , and carbonate ions, CO32In order for the charges to balance we need two ammonium ions for every one carbonate ion therefore the formulae becomes (NH4)2CO3 5) Using the ions given below, write the overall formulae of the following ionic compounds: a) zinc oxide c) copper sulfate b) potassium sulfate d) calcium hydroxide (4 marks) zinc = Zn2+, copper = Cu2+, potassium = K+, calcium = Ca2+, sulfate = SO42-, hydroxide = OH-, oxide = O2- 6) Write a symbol equation to show that magnesium carbonate decomposes into magnesium oxide and carbon dioxide. [magnesium ion = Mg2+] (3 mark) For help with this section, try the following link; http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/bonding/ionic_bondingrev7.shtml Section 5 – Nuclear Reactions During GCSE Physics you studied radioactive particles and nuclear reactions. These topics will be revisited during the first A level topic; 7) Fill in the following table for the properties of α, β and γ emissions: Type of emission Property α β γ relative charge relative mass range in air (eg few cm, few m, many metres) stopped by deflection by electrical field (eg high, low or nil) (5 marks) 8) Write a nuclear equation for the α decay of 238Pu 94 (2 marks) 9) Write a nuclear equation for the β decay of 14C 6 (2 marks) 10) In a nuclear fusion reaction, two light atomic nuclei join together to form a single heavier nucleus of a new element. Write a nuclear equation to show the fusion of a hydrogen-1 nucleus with a hydrogen2 nucleus. (2 marks) For help with this section, try the following link; http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway_pre_2011/living_future/4_nucle ar_radiation1.shtml http://www.chemteam.info/Radioactivity/Writing-Alpha-Beta.html