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DP IB Chemistry: SL

Topic Questions

Home / IB / Chemistry: SL / DP / Topic Questions / 1. Stoichiometric Relationships / 1.2 Reacting Masses & Volumes / Structured Questions: Paper 2


1.2 Reacting Masses & Volumes

Question 1a

Marks: 1
a)
Citric acid, C6H8O7 , is present in lemon juice and is classed as a weak acid. 10.00 cmof citric acid is reacted with sodium hydroxide, NaOH (aq) , with a concentration of 12.0 g dm-3 to form sodium citrate, Na3C6H5O, and water. 32.10 cm3 of sodium hydroxide was required to react with the lemon juice. 

State the balanced equation for this reaction. 
[1]

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    Key Concepts
    Balancing equations

    Question 1b

    Marks: 1
    b)
    Calculate the mass, in grams, of sodium hydroxide that reacted with the lemon juice. 
    [1]

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      Question 1c

      Marks: 3
      c)
      Determine the concentration, in mol dm-3, of citric acid in the sample of lemon juice. 
      [3]

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        Question 2a

        Marks: 3
        a)
        A group of students investigated the rate of reaction between sodium thiosulfate and hydrochloric acid by measuring the amount of time taken for a cross marked on a piece of paper to become obscured by a yellow precipitate. 

        Na2S2O3 (aq) + 2HCl (aq) → 2NaCl (aq) + SO2 (g) + H2O (l) + S (s) 

        9

        Initially they measured out 15.00 cm3 of 0.900 mol dm-3 hydrochloric acid and then added 40.00 cm3 of 0.0150 mol dm-3 aqueous sodium thiosulfate.

        The mark on the paper was obscured 38 seconds after the solutions were mixed.

        Their teacher made up 3.00 dm3 of sodium thiosulfate solution using sodium thiosulfate pentahydrate crystals, Na2S2O3•5H2O. 

        Calculate the required mass, in grams, of these crystals. Give your answer to 2 decimal places. 
        [3]

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          Question 2b

          Marks: 4
          b)
          Using section 2 of the Data booklet, calculate the volume of gas produced, in dm3, in this reaction if it were collected at a temperature of 300 K and 1.00 x 105 Pa. 
          [4]
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            Key Concepts
            Ideal Gas Equation

            Question 2c

            Marks: 1
            c)
            A different group of students decided to measure the rate of reaction by collecting the volume of sulfur dioxide produced over a period of time.

            The students attempted to collect the gas in a measuring cylinder over water, but were unsuccessful. Suggest why they were unsuccessful.  
            [1]

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              Question 2d

              Marks: 2
              d)
              Determine the pH of the acid used and suggest how pH could be used to measure the rate of reaction. 
              [2]
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                Key Concepts
                Acid-Base Calculations

                Question 2e

                Marks: 3
                e)
                Determine the reagent in excess in this reaction and state the amount, in moles, that will be in excess. 

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                  Question 3a

                  Marks: 1
                  a)
                  Phosphine, PH3, is a gas formed by heating phosphorous acid, H3PO3, in the absence of air, as shown in the equation below.

                  4H3PO3 (s) → PH3 (g) + 3H3PO(s)

                     3.45 × 10−2 mol of H3PO3 is completely decomposed by this reaction.

                  State the expected molecular shape and expected bond angle in PH3 (g).
                  [1]
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                    Question 3b

                    Marks: 5
                    b)
                    Calculate the volume of phosphine gas formed, in cm3, at 100 kPa pressure and 210 °C.
                    [5]
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                      Key Concepts
                      Ideal Gas Equation

                      Question 3c

                      Marks: 3
                      c)
                      1.85 g of white phosphorus was used to make phosphine according to the equation.

                      P(s) + 3OH− (aq) + 3H2O (l) → PH(g) + 3H2PO2− (aq)

                      This phosphorus was reacted with 75.00 cm3 of 4.50 mol dm-3 sodium hydroxide solution. Deduce, showing your working, which was the limiting reagent. 
                      [3]

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                        Question 3d

                        Marks: 1
                        d)
                        Using section 2 of the Data booklet determine the volume of phosphine, measured in cm3 at standard temperature and pressure, that was produced. Give your answer to 3 significant figures. 
                        [1]

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                          Key Concepts
                          Molar Gas Volume

                          Question 4a

                          Marks: 2
                          a)
                          A student carried out an experiment involving a solution of potassium dichromate(VI), K2Cr2O7, with iron(II) sulfate, to find the mass of FeSO4.7H2O in an impure sample, A

                          The student recorded the mass of A, dissolved the sample in water and then made the solution up to 500 cm3. After an excess was added, the student found that 25.00 cm3 of this solution reacted with 22.10 cm3 of a 0.020 mol dm–3 solution of K2Cr2O7.

                          Deduce the full equation for the reaction between acidic Cr2O72- (aq) and Fe2+ (aq) to form Cr3+ (aq) and Fe3+ (aq).


                          [2]

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                            Key Concepts
                            Half equations

                            Question 4b

                            Marks: 4
                            b)
                            Use section 6 of the Data booklet to determine the mass, in grams, of FeSO4.7H2O in sample, A. Give your answer to three significant figures.
                            [4]
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                              Question 4c

                              Marks: 4
                              c)
                              A student performs a titration to determine the molar mass and structure of a dicarboxylic acid, X, which only contains carbon, hydrogen and oxygen. 


                              The student prepares a 250.0 cm3 solution from 1.513 g of X.

                              The solution of X is added to the burette and titrated with 25.00 cm
                              3 aliquot of 0.112 mol dm-3 NaOH (aq). 

                              The student recorded their results in the table below:

                                Titration 1 Titration 2 Titration 3
                              Final burette reading / cm3 28.60 27.95 29.45
                              Initial burette reading / cm3 1.10 0.70 2.10
                              Volume added / cm3 27.50 27.25 27.35

                              i)
                              Determine the mean volume, in dm3, of the titre. 
                              [1]

                              ii)
                              Determine the amount, in moles, of X in the original sample.
                                 [3]

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                                Key Concepts
                                Titrations

                                Question 4d

                                Marks: 2
                                d)
                                Using section 6 in the Data booklet, suggest a structure for X.
                                [2]



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                                  Question 5a

                                  Marks: 4
                                  a)
                                  An empty 1.5 dm3 Tupperware container has been kept in the fridge without a lid at 5 °C. The container is removed from the fridge and allowed to reach a temperature of 21 °C. Using your knowledge of Charles's Law, determine the volume of gas, in cm3, that escaped from the container. 
                                  [4]

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                                    Key Concepts
                                    Real Gas Behaviour

                                    Question 5b

                                    Marks: 2
                                    b)
                                    A balloon contains 2500 mL of helium gas at a temperature of 75 °C. Determine the new volume in mL of the gas when the temperature changes to 55 °C assuming the pressure is constant. Give your answer to three significant figures. 
                                    [2]
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                                      Key Concepts
                                      Real Gas Behaviour

                                      Question 5c

                                      Marks: 2
                                      c)
                                      A 10.0 L container of helium gas with a pressure of 33 000 Pa at 0 °C is heated until the new pressure is 200 000 Pa. Determine the new temperature of the gas assuming the volume remains constant. 
                                      [2]

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                                        Key Concepts
                                        Real Gas Behaviour