Chemistry Mark Scheme 2020
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Questions and Answers

Which box shows two different particles in the same space that are not chemically joined?

  • Box 1
  • Box 2 (correct)
  • Box 3
  • Box 4

    • Which boxes show a mixture?

  • Boxes 3 and 4
  • Boxes 1 and 3 (correct)
  • Boxes 1 and 2
  • Boxes 2 and 3

    • What does box 5 show?

    Two different elements chemically bonded together.

    How are the elements in the periodic table arranged?

    <p>Order of proton number (A)</p> Signup and view all the answers

    Elements in the same group of the periodic table have the same:

    <p>Number of electrons in the outer shell. (D)</p> Signup and view all the answers

    What must be below the dyes/start line in an experiment examining chromatography?

    <p>The level of water.</p> Signup and view all the answers

    What must the start line in an experiment examining chromatography be drawn in?

    <p>Pencil (B)</p> Signup and view all the answers

    Which of the following are true about the green food coloring used in the described experiment? (Select all that apply)

    <p>It contains dye B. (E), It contains an unknown dye. (F), It contains dye D. (G)</p> Signup and view all the answers

    How do you calculate the Rf value for a dye in chromatography?

    <p>Divide the distance moved by the dye by the distance moved by the solvent.</p> Signup and view all the answers

    Dye A is soluble in water.

    <p>False (B)</p> Signup and view all the answers

    Which of the following is the correct description of the reaction that occurs when two solutions are mixed to form an insoluble solid?

    <p>Precipitation (B)</p> Signup and view all the answers

    What is not a suitable method of drying a solid in the lab?

    <p>Drying in a hot oven over Bunsen burner (A)</p> Signup and view all the answers

    What type of chemical reaction is needed to precipitate a solid?

    <p>Double displacement.</p> Signup and view all the answers

    What type of chemical reaction is used to form silver chloride precipitate?

    <p>Double displacement (B)</p> Signup and view all the answers

    What is the formula of silver nitrate?

    <p>AgNO3</p> Signup and view all the answers

    What is the formula of silver chloride?

    <p>AgCl</p> Signup and view all the answers

    What is the molar mass of silver chloride?

    <p>143.5 g/mol</p> Signup and view all the answers

    What is the key characteristic of a metallic solid that allows for its malleability?

    <p>Layers of atoms are able to slide over each other.</p> Signup and view all the answers

    Ions in a metallic bond can move freely.

    <p>False (B)</p> Signup and view all the answers

    What is the chemical equation for the reaction of bromide ions to form bromine?

    <p>2Br- → Br2 + 2e-</p> Signup and view all the answers

    Describe the attraction of lead ions to an electrode during electrolysis.

    <p>Lead ions (Pb2+) are attracted to the negative electrode.</p> Signup and view all the answers

    Explain how lead ions are reduced in the electrolysis process.

    <p>Lead ions gain two electrons at the negative electrode, forming lead atoms.</p> Signup and view all the answers

    What role does the metal connecting the electrodes in an electrolysis setup fulfill?

    <p>It completes the circuit and allows electrons to flow between the electrodes.</p> Signup and view all the answers

    What are two observations when lithium is added to water?

    <p>A colourless solution forms. (B), Lithium floats on the surface. (F)</p> Signup and view all the answers

    A squeaky pop sound is produced when lithium is mixed with air.

    <p>True (A)</p> Signup and view all the answers

    When potassium is added to water, which of these observations can be made? (Select all that apply)

    <p>Catches alight and burns/produces a flame. (A), Moves more quickly. (B), Gets smaller and disappears more quickly. (C), Turns into a ball. (D), Produces bubbles/fizzing/effervescence more rapidly (E)</p> Signup and view all the answers

    Explain why potassium is more reactive than lithium.

    <p>Potassium has more electron shells than lithium, making the outer electron easier to lose.</p> Signup and view all the answers

    What is the volume of 0.0357 mol of hydrogen gas at room temperature and pressure?

    <p>857 cm3</p> Signup and view all the answers

    What is the concentration of a LiOH solution if 0.15 dm3 of the solution contains 0.00497 mol of LiOH?

    <p>0.0331 mol/dm3</p> Signup and view all the answers

    Describe the process of fractional distillation in relation to crude oil, including the key features of the setup and the results.

    <p>A fractionating column is used, with a heat source at the bottom and a cooling system at the top, creating a temperature gradient. The crude oil is heated, and the different components vaporize at their respective boiling points. These vapors rise through the column, condensing and being collected at different heights depending on their boiling points, resulting in separate fractions of hydrocarbons.</p> Signup and view all the answers

    What effect does increasing the concentration of reactants have on the rate of a reaction?

    <p>Increased rate. (B)</p> Signup and view all the answers

    The rate of the forward reaction is always equal to the rate of the reverse reaction in a reversible reaction.

    <p>False (B)</p> Signup and view all the answers

    In a reversible reaction, the concentrations of products and reactants remain constant at equilibrium.

    <p>True (A)</p> Signup and view all the answers

    What is Le Chatelier's Principle?

    <p>When a change of conditions is applied to a system at equilibrium, the position of equilibrium shifts in a direction that relieves the stress.</p> Signup and view all the answers

    An increase in temperature shifts the position of equilibrium towards the endothermic direction in a reversible reaction.

    <p>True (A)</p> Signup and view all the answers

    If an increase in temperature shifts the position of equilibrium towards the endothermic direction, then the reverse reaction must be exothermic.

    <p>True (A)</p> Signup and view all the answers

    What is the displayed formula of propanoic acid?

    <p>H-C-C-C-O-H | | | | | | H H H H H H</p> Signup and view all the answers

    What is the displayed formula of butan-1-ol?

    <p>H-C-C-C-C-O-H | | | | | | H H H H H H</p> Signup and view all the answers

    Which of the following can be added to propanoic acid to produce carbon dioxide?

    <p>A named carbonate or hydrogencarbonate. (A), A metal, such as magnesium, aluminium, zinc, or iron. (C)</p> Signup and view all the answers

    What observation is made when a carbonate or hydrogencarbonate is added to propanoic acid?

    <p>Effervescence/bubbles/fizzing occurs. (A)</p> Signup and view all the answers

    Which of the following can be added to propanoic acid to produce an ester?

    <p>A named alcohol and concentrated sulfuric acid, warmed. (E)</p> Signup and view all the answers

    The reaction of propanoic acid and an alcohol to form an ester is reversible.

    <p>True (A)</p> Signup and view all the answers

    Describe the characteristic smell of an ester.

    <p>Sweet.</p> Signup and view all the answers

    Draw the activation energy profile for the reaction of ethene and hydrogen to form ethane.

    <p>Energy activation energy C2H4 + H2 ΔΗ C2H6</p> Signup and view all the answers

    How do you determine the enthalpy change (ΔH) for a reaction?

    <p>Calculate the difference between the total energy needed to break bonds in reactants and the total energy released when bonds form in products.</p> Signup and view all the answers

    Flashcards

    What is an element?

    A substance containing only one type of atom.

    What is a compound?

    A substance containing two or more different types of atoms chemically combined.

    What is a mixture?

    A substance containing two or more different substances that are not chemically combined, and can be separated by physical means.

    What is a homogeneous mixture?

    A homogeneous mixture is a mixture where the components are evenly distributed throughout the mixture.

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    What is a heterogeneous mixture?

    A heterogeneous mixture is a mixture where the components are not evenly distributed throughout the mixture.

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    What is the atomic number?

    The number of protons in the nucleus of an atom.

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    What is the mass number?

    The total number of protons and neutrons in the nucleus of an atom.

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    What are isotopes?

    Atoms of the same element that have the same number of protons but different number of neutrons.

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    What are valence electrons?

    The electrons in the outermost shell of an atom.

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    What is a metal?

    An element that has a tendency to lose electrons in chemical reaction.

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    What is a non-metal?

    An element which tends to gain electrons in chemical reaction.

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    What is combustion?

    A chemical reaction where a substance reacts with oxygen.

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    What is thermal decomposition?

    A chemical reaction where a substance is broken down by heat.

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    What is neutralisation?

    A chemical reaction where an acid reacts with a base.

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    What is a redox reaction?

    A chemical reaction where electrons are transferred from one substance to another.

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    What is fractional distillation?

    The process of separating components of a mixture based on their boiling points.

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    What is the activation energy?

    The minimum amount of energy needed for a reaction to occur.

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    What is the enthalpy change (ΔH)?

    The difference in enthalpy between reactants and products.

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    What is an exothermic reaction?

    A reaction that releases heat into the surroundings.

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    What is an endothermic reaction?

    A reaction that absorbs heat from the surroundings.

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    What is a catalyst?

    A substance that speeds up the rate of a reaction without being consumed in the process.

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    What is equilibrium?

    The rate of the forward reaction equals the rate of the reverse reaction.

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    What happens to the position of equilibrium when the temperature is increased?

    The position of equilibrium shifts to favor the endothermic reaction.

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    What is oxidation?

    A reaction that involves the gain of oxygen or loss of hydrogen.

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    What is reduction?

    A reaction that involves the gain of hydrogen or the loss of oxygen.

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    What are hydrocarbons?

    A group of organic compounds containing only carbon and hydrogen.

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    What is esterification?

    A reaction that involves the joining of molecules with the elimination of water.

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    What is hydrolysis?

    A process that involves the breakdown of large molecules into smaller molecules by the addition of water.

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    What is concentration?

    A measure of the amount of a substance dissolved in a given volume of solvent.

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    What is extraction?

    The process of separating components of a mixture based on their solubility in a particular solvent.

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    What is a carboxylic acid?

    A chemical compound containing a carboxyl group (-COOH).

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    What is an alcohol?

    A chemical compound containing a hydroxyl group (-OH).

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    What is addition reaction?

    A type of organic reaction where a double bond is broken and two new single bonds are formed.

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    What is elimination reaction?

    A type of organic reaction where a molecule is removed from the reactant.

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    What is a substitution reaction?

    A type of organic reaction where an atom or group of atoms is replaced by another atom or group.

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    Study Notes

    Mark Scheme (Results)

    • Pearson Edexcel International GCSE in Chemistry (4CH1)
    • January 2020
    • Paper 2CR

    General Marking Guidance

    • All candidates receive the same treatment
    • Examiners mark the first candidate the same way they mark the last
    • Mark schemes should be applied positively
    • Examiners should mark according to the mark scheme, not their perception of grade boundaries
    • There is no ceiling on achievement
    • All marks on the mark scheme should be used appropriately
    • Examiners should award full marks if deserved
    • Examiners should award zero marks if a response is not worthy of credit
    • Where judgement is required, mark schemes provide the principles, with exemplification that may be limited
    • When examiners are in doubt, the team leader must be consulted
    • Crossed-out work should be marked unless the candidate replaces it with an alternative response

    Question 1 (a)(i)

    • The correct answer is B because box 2 contains two different particles in the same space that are not chemically joined
    • A is incorrect because box A shows an element
    • C is incorrect because box C shows an element
    • D is incorrect because box 4 shows a compound

    Question 1 (a)(ii)

    • The correct answer is C because boxes 1 and 2 contain one type of atom only
    • A is incorrect because box 2 shows a mixture
    • B is incorrect because box 2 shows a mixture
    • D is incorrect because box 4 shows a compound

    Question 1 (a)(iii)

    • M1: box 5 shows two (different) elements
    • M2: chemically bonded (together)

    Question 2 (a)

    • M1: level of the water must be below the dyes/start line
    • ACCEPT dyes/start line should be above water level

    Question 2 (b)(i)

    • M1: contains (dye) B and (dye) D
    • M2: contains an unknown dye
    • M3: does not contain A or C
    • M4: contains three dyes

    Question 2 (b)(ii)

    • M1 (distance moved by solvent correctly measured)= 9.5cm
    • ALLOW a tolerance of ±2mm
    • M2 use of RfR_fRf​ = distancemovedbythedyedistancemovedbythesolvent\frac{distance moved by the dye}{distance moved by the solvent}distancemovedbythesolventdistancemovedbythedye​
    • M3 evaluation of RfR_fRf​

    Question 2 (b)(iii)

    • (dye A) is not soluble in water
    • ALLOW solvent for water

    Question 3 (a)

    • The correct answer is B because the reaction of two solutions to produce an insoluble solid is precipitation
    • A is incorrect because this reaction is not neutralisation
    • C is incorrect because this reaction is not a redox reaction
    • D is incorrect because this reaction is not thermal decomposition

    Question 3 (b)

    • M1: wash the solid with (deionised) water;
    • M2: suitable method of drying solid (e.g. dry between filter papers/on paper towel/in (warm) oven/in a desiccator)

    Question 3 (c)

    • Any one from:
      • M1 (hydrochloric acid/it) contains chloride ions
      • M2 (hydrochloric acid/it) produces a (white) precipitate with silver nitrate
      • M3 (hydrochloric acid/it) reacts with silver nitrate

    Question 3 (d)

    • M1 n(AgNO3 or AgCl) = 0.0025
    • M2 (mass AgCl) = 0.0025 x 143.5 = 0.35(9)g

    Question 4 (a)(i)

    • M1: layers of atoms/positive ions
    • M2: can slide over one another

    Question 4 (b)(i)

    • ions cannot move

    Question 4 (b)(ii)

    • 2Br- → Br2 + 2e-

    Question 4 (b)(iii)

    • M1: lead ions (are positive and) are attracted to the negative electrode / Pb2+ (ions) are attracted to the negative electrode
    • M2: lead ions gain electrons / Pb2+ (ions) gain electrons (to form lead)

    Question 4 (b)(iv)

    • metal or lead connects the electrodes or completes the circuit

    Question 5 (a)(i)

    • Any two from:
      • M1 (lithium) moves (on the surface)
      • M2 (lithium) gets smaller/disappears
      • M3 colourless solution forms

    Question 5 (a)(ii)

    • (when mixed with air)
      • lit spill/splint or flame gives (squeaky) pop

    Question 5 (b)(i)

    • Any one from:
      • M1 more rapid bubbles/fizzing/effervescence
      • M2 turns into a ball
      • M3 moves more quickly
      • M4 catches alight / burns / produces a flame

    Question 5 (b)(ii)

    • M1 potassium has more shells than lithium
    • M2 (therefore) there is less attraction between the outer shell/electron and the nucleus
    • M3 so the electron in the outer shell is more easily lost

    Question 5 (c)(i)

    • M1 n(Li)= 0.500 OR 0.0714
    • M2 n(H2) = 0.0714 OR 0.0357
    • M3 volume of H2 =( 0.0357 x 24000)= 857 (cm³)

    Question 5 (c)(ii)

    • M1 n(H2SO4)= 0.02485 x 0.1 OR 0.002485
    • M2 n(LiOH) = 2 x 0.002485 OR 0.00497
    • M3 concentration of LiOH = 0.0331 (mol/dm³)

    Question 6 (a)

    • M1 (use) fractional distillation / fractionating column / fractionating tower
    • M2 (crude oil) heated / vaporised
    • M3 column is cooler at top / hotter at the bottom / idea of temperature gradient

    Question 6 (b)(i)

    • M1 particles/molecules are closer together
    • M2 therefore more (successful) collisions per unit time

    Question 6 (b)(ii)

    • M1 (a catalyst provides) an alternative pathway
    • M2 of lower activation energy

    Question 6 (b)(iii)

    • increase the temperature

    Question 7 (a)(i) CO2

    • ALLOW (otherwise) ethanol will be oxidised or react with oxygen

    Question 7 (a)(ii)

    • ALLOW fermentation/reaction/respiration needs to be anaerobic
    • ALLOW (otherwise) ethanol would not be formed /CO2 and H2O would be formed

    Question 7 (a)(iii)

    • M1 (reaction is catalysed by) enzymes (in yeast)
    • M2 which will denature (above 40°C)

    Question 7 (a)(iv)

    • M1 maximum mass of ethanol = 8 x 46 = 368 (g)
    • M2 55.2 x 100 (=15%)/368

    Question 7 (b)(i)

    • M1 rate of the forwards reaction = the rate of the backwards reaction
    • M2 the concentrations of reactants and products remain constant

    Question 7 (b)(ii)

    • M1 an increase in temperature shifts the (position of) equilibrium in the endothermic direction (so backwards reaction is endothermic)
    • M2 so forward reaction is exothermic

    Question 7 (c)(i)

    • M1 (displayed formula of A - propanoic acid)
    • M2 (displayed formula of B - butan-1-ol)

    Question 7 (c)(ii)

    • M1 add a named carbonate or hydrogencarbonate
    • M2 effervescence/bubbles/fizzing
    • OR
    • M1 add a suitable named metal (e.g., magnesium, aluminium, zinc, iron)
    • M2 effervescence/bubbles/fizzing
    • OR
    • M1 add a named alcohol (and some concentrated sulfuric acid and warm)
    • M2 sweet smell (of an ester)

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    Pearson Edexcel International GCSE in Chemistry (4CH1) Paper 2CR Mark Scheme January 2020 PDF

    Description

    This quiz focuses on the Pearson Edexcel International GCSE Chemistry (4CH1) mark scheme for Paper 2CR from January 2020. It includes guidance for examiners on how to grade responses and specific details regarding marking principles. Perfect for candidates and educators preparing for Chemistry assessments.

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