IGCSE 2020 4CH1/1C June Edexcel Chemistry

IGCSE 2020 4CH1/1C June (pdf)

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1. This question is about chemical elements.
   Use the Periodic Table to help you answer this question.
   (a) (i) Identify the element with atomic number 5
   (ii) Give the symbol of a metallic element in Period 3
   (iii) Identify the element whose atoms contain 14 protons.
   (iv) Identify the element whose atoms have the electronic configuration 2.5
   (v) Give the name of the compound formed between oxygen and the element with atomic number 13
   (b) The position of an element in the Periodic Table can be used to predict its properties.
   (i) Which group contains elements that are all unreactive?
   (ii) Which of these is the least reactive element in Group 1?
2. (a) The boxes list changes that may happen in a laboratory and the names of some changes.
   Draw one straight line from each change to its correct name
   (b) A student has two solids, X and Y.
   One of these solids is a pure substance and the other is a mixture.
   Describe how the student could identify which solid is pure and which is a mixture by measuring a physical property of each solid.
3. This question is about metals.
   (a) Metals can be arranged in a reactivity series based on their reactions with water and their reactions with dilute hydrochloric acid.
   The table shows how four metals, P, Q, R and S, react with water and with dilute hydrochloric acid.
   (i) Identify which of the metals P, Q, R or S could be gold.
   (ii) Suggest why the reaction between metal R and dilute hydrochloric acid was not done
   (iii) Use the information in the table to place the metals in order of reactivity from most reactive to least reactive
   (b) Zinc is used to coat iron gates to prevent the iron from rusting.
   (i) State the name of this method of preventing iron from rusting.
   (ii) State another method of preventing iron from rusting.
   (c) A mixture of zinc powder and copper(II) oxide is heated.
   The chemical equation for the reaction that takes place is
   Zn + CuO → ZnO + Cu
   (i) State how the reaction shows that zinc is more reactive than copper
   (ii) Explain which substance is the oxidising agent.
   
4. Sodium hydroxide dissolves in water, forming a strongly alkaline solution.
   Ammonia dissolves in water, forming a slightly less alkaline solution.
   (a) (i) Identify the ion that makes the sodium hydroxide solution alkaline
   (ii) What is a possible pH of ammonia solution?
   (b) When ammonia solution reacts with sulfuric acid, a neutralisation reaction occurs and ammonium sulfate forms.
   (i) How does the sulfuric acid act in this reaction?
   (ii) The diagram shows a beaker containing some ammonia solution and a few drops of phenolphthalein indicator.
   Dilute sulfuric acid is added to the beaker until it is in excess.
   What are the colours of the phenolphthalein indicator before and after adding excess sulfuric acid?
   (c) Ammonium sulfate is used by gardeners as a fertiliser because it contains nitrogen.
   (i) Explain why the chemical formula of ammonium sulfate is (NH₄)₂SO₄
   Refer to the charges on the ions in your answer
   (ii) Calculate the relative formula mass of ammonium sulfate, (NH₄)₂SO₄
   (iii) Calculate the mass, in grams, of nitrogen in 1.0kg of ammonium sulfate

5. (a) Chlorine, bromine and iodine are elements in the Periodic Table.
   Explain how the position of these elements in the Periodic Table depends on their electronic configurations.
   (b) Chlorine reacts with methane to form CH3Cl and HCl
   (i) State the condition necessary for this reaction.
   (ii) Give the equation for this reaction.
   (iii) The bonds in a molecule of CH₃Cl are covalent.
   Explain, in terms of electrostatic attractions, what is meant by a covalent bond
   (iv) Draw a dot‑and‑cross diagram for a molecule of CH₃Cl
   Show only the outer electrons of the atoms
   (v) CH₃Cl has a simple molecular structure.
   Explain why CH₃Cl has a low boiling point.
   (c) Graphite is another substance that contains covalent bonds.
   The diagram shows the structure of graphite.
   Most covalent substances do not conduct electricity.
   Explain why graphite is able to conduct electricity
6. The table shows the molecular formulae of six organic compounds, A, B, C, D, E and F
   (a) (i) Explain which homologous series compound B belongs to.
   (ii) Give the letter of the compound that has the same empirical formula as its molecular formula.
   (iii) Compound F exists as two isomers.
   Explain what is meant by the term isomers.
   Include the structures of the two isomers of compound F in your answer
   (b) Describe how compound D can be obtained from crude oil using the industrial process of fractional distillation.
   (c) Compound C can be used to make a polymer.
   (i) State the type of polymer formed from compound C.
   (ii) Name the polymer formed from compound C.
   (iii) Draw the structure of this polymer.
   Include the displayed formula of the repeat unit
7. Dilute hydrochloric acid reacts with a solution of sodium thiosulfate (Na2S2O3) to form a precipitate.
   The equation for the reaction is
   Na₂S₂O₃(aq) + 2HCl(aq) → 2NaCl(aq) + S(s) + H₂O(l) + SO₂(g)
   (a) State the name of the precipitate that forms.
   (b) The reaction is often used to investigate rates of reaction.
   The diagram shows the apparatus a student uses to investigate the effect of temperature on the rate of the reaction.
   This is the student’s method.

• pour 50cm³ of cold sodium thiosulfate solution into a conical flask and heat it to 20°C
• draw a cross (X) on a piece of paper and place it under the flask
• add 5cm³ of dilute hydrochloric acid to the flask
• look at the cross from above and record the time taken until the cross cannot be seen
  The student repeats the experiment four times, using sodium thiosulfate solution at a different temperature each time.
  He keeps the volumes of sodium thiosulfate solution and hydrochloric acid constant in each experiment.
  Give two other factors that the student should keep constant
  (c) The table shows the student’s results.
  The highest temperature the student uses is 60°C because he thinks the results might not be as accurate at temperatures higher than 60°C.
  Suggest a reason why the results might not be as accurate at temperatures higher than 60°C.(d) The student wants to compare the rates of the reaction at the different temperatures.
  He uses this formula to obtain a value for each rate of reaction
  The table shows the value of the rate of reaction at each temperature.
  Plot the values of temperature and rate of reaction on the grid.
  Draw a curve of best fit through the points.
  (e) (i) Use the graph to determine a value for the rate of the reaction at 45°C.
  Show on the graph how you obtained your answer.
  (ii) Calculate the time that it would take for the cross not to be seen at 45°C
  (iii) Describe the relationship between rate of reaction and temperature shown by the graph.
  (f) Explain, in terms of particle collision theory, the effect that increasing the temperature has on the rate of a reaction.
  

8. A student uses this apparatus to investigate the heat energy change when a salt dissolves in water to form a solution.
   This is the student’s method.

• add 50cm³ of distilled water to a polystyrene cup
• record the initial temperature of the water
• add a known mass of solid anhydrous copper(II) sulfate to the polystyrene cup and stir the solution with the thermometer until all the solid has dissolved
• record the maximum temperature of the copper(II) sulfate solution
  (a) (i) Name the piece of apparatus the student should use to add the distilled water to the polystyrene cup.
  (ii) The student stirs the solution to help the solid dissolve more quickly.
  Suggest another reason why the student stirs the solution
  (iii) State the colour of the copper(II) sulfate solution
  (b) The diagram shows the temperatures in one experiment
  Complete the table, giving all values to the nearest 0.1°C
  (c) In a second experiment, when a student dissolves the anhydrous copper(II) sulfate in 50cm³ of distilled water, the increase in temperature is 3.3°C.
  (i) Show that the heat energy change (Q) in this second experiment is approximately 700J.
  [for water, c = 4.2J/g/°C]
  [mass of 1.0cm³ of water = 1.0g]

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