w w w e tr .X m eP UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Ordinary Level e ap .c rs om MARK SCHEME for the May/June 2011 question paper for the guidance of teachers 5070 CHEMISTRY 5070/21 Paper 2 (Theory)‚ maximum raw mark 75 This mark scheme is published as an aid to teachers and candidates‚ to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that
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calcium chloride were used up. Also to see if there’s any alterations like mass differentials. Objectives: 1. To introduce the concept of “limiting factor” in a chemical reaction 2. To practice a. Writing a balanced equation b. Determining the number of moles of each reactant and product c. Deciding which chemical is the limiting factor d. Predict theoretical yield e. Determine actual yield f. Use error discussion Materials: * 2 beakers * 2
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Determining the enthalpy change for the thermal decomposition of potassium hydrogen carbonate into potassium carbonate. Controlled Variables: 1. Volume of HCl ± 0.5 cm3 (± 2%) 2. Concentration of HCl‚ 3. Same mass of K2CO3 and KHCO3 within specified ranges of 2.5 – 3.0g and 3.25 – 3.75g respectively 4. Same calorimeter used i.e. polystyrene cup is used in this experiment 5. Same thermometer will be used ± 0.10K 6. Same source of K2CO3‚ KHCO3 and HCl Raw Data Results: The raw
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Chemistry‚ 2014 UNIT 1 – MATTER TRENDS AND CHEMICAL BONDING History of the atom DEMOCRITUS Smallest particle of matter is called an atom Atoms are in constant motion and have empty space between them ARISTOTLE 4 element theory of matter (earth‚ air‚ water‚ fire) Had different combinations of the 4 qualities: hot‚ cold‚ dry‚ moist JOHN DALTON Expanded on Democritus’s theory: All matter is composed of tiny‚ indivisible particles All atoms of an element have identical properties
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partial pressure of the hydrogen gas collected in the gas collection tube. The partial pressure of the hydrogen gas is 1.07 atm 3. Calculate the moles of hydrogen gas collected. pv=mrt ; n= .0013mol of hydrogen gas 4. If magnesium was the limiting reactant in this lab‚ calculate the theoretical yield of the gaseous product. Show all steps of your calculation. 0.03184 g Mg(1mol Mg/ 24.3050 g Mg)= 0.0013mols Mg 0.0013mols Mg(1mol H2/ 1mol Mg)= .0013 1. Determine the percent yield of this reaction
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on ivy leaf disks in a bicarbonate solution. The function of the sodium bicarbonate in this experiment was to provide a sufficient amount of carbon dioxide (CO2) for the photosynthesis process to occur. Without CO2 or any of the other necessary reactants‚ glucose nor oxygen cannot be produced. The leaves rise and sink due to photosynthesis occurring in the plant cells. As the carbon from the sodium bicarbonate is consumed‚ the leaf disks sink. Then as photosynthesis continues‚ oxygen is produced
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Report Submitted: June 21‚ 2013 Title: Properties of Gases Purpose: To analyze a few physical and chemical properties of gases as well as using those properties to identify the gases. Procedure: * For Hydrogen I placed a piece of Zn metal into a test tube with diluted HCl. * To produce oxygen I added Hydrogen peroxide to manganese. * Next‚ I added baking soda to vinegar. This caused a quick and energetic reaction! The gas from the reaction I pumped into some Limewater. * Then
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collection tube. (3 points) ! 1.1 atm = 0.026 atm + h2 ! ! ! 3. Calculate the moles of hydrogen gas collected. (4 points) ! ! ! n = 1.074 atm x 0.03 L / 0.0821 x 295.15 K = 0.00133 mol H2 ! ! ! ! 4. If magnesium was the limiting reactant in this lab‚ calculate the theoretical yield of the gaseous product. Show all steps of your calculation. (4 points) ! .032 g Mg * 1 mol Mg / 24.305 g Mg * 1mol h2 / 1 mol Mg = 0.0131 mol ! ! ! ! ! 5. Determine the percent
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transfer catalysts (PCT) are used to catalyze reactions involving chemical species which are present in different phases. These types of reactions are known as a homogeneous two phase reactions and are usually very slow because the two primary reactants (in this case CHCl3 and NaOH) are in different phases. The reaction catalyzed in this experiment is the addition of a dichlorocarbene to cyclohexene. The dichlorocarbene must first be generated in solution and this is done using the strong base‚
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its transition state‚ which in this case‚ is the endo isomer. To ease the concerns of orbital overlap between the HOMO (Highest Occupied Molecular Orbital) of cyclopentadiene with the LUMO (Lowest Unoccupied Molecular Orbital) maleic anhydride‚ reactants are used which possess electron withdrawing groups on the dienophile (maleic anhydride) and electron donating groups on the diene (cyclopentadiene). (2) Side reactions in this experiment include the reaction of cyclopentadiene with itself as it will
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