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    (Original post by abxo)
    Oh **** i found the wrong salt omg 😂😂 i got 65.5% for the other BaCl2 LoOL how many marks do u think i would have dropped? Im saying 2 out of the four because all my numbers were right! Hopefully
    I think you'll lose one for stating the wrong percentage. You'll get one for:
    Saying BaSO4,
    Working out mass of Barium,
    Working out mass of BaCl2,
    Working out percentage of MgCl2,
    if you were to do it my way.

    That's my thoughts anyway.

    P.S. IF the examiner/mark scheme is *suuuuuuper* nice, so don't expect it, if you were to explicitly state the percentage of solid that is BaCl2 is the correct percentage, then you might get the mark for implying the percentage of MgCl2. I doubt this greatly, but it's not out of the picture.
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    (Original post by DaVinciGirl)
    If you know anymore questions or answers please reply and the number of marks.
    What is the full electronic configuration of Al? 1s2,2s2,2p6,3s2,3p1

    What is the full electronic configuration for Cr+3? 1s2,2s2,2p6,3s2,3p6,3d3

    What is the formula of the ion with same electronic configuration of Krypton?
    Sr2+ (strontium)

    What compound has a +2 and -3 ions and has the same number electrons as Argon?
    Ca3P2

    Which ion has a smaller atomic radius Mg2+ or Na+?
    Mg 2+
    because has the same number of electrons, same shielding but more protons. So greater nuclear charge and attraction for outer electrons.

    What is the first ionisation energy of Na?
    Na (g) --> Na+ (g) + e-
    Diagram-Mark where the Mg or was it Si?
    Was and then mark the point where Sulphur was on the First ionisation graph.
    Mg/Si should have been above so the line was increasing.
    Sulphur should have been below Phosphorus but above Silicon.

    Why does Sulphur have a different first ionisation energy compared to Phosphorus?
    -Both have same shielding and in the same orbital the 3p orbital
    -Sulphur is paired with an electron in the 3p orbital whilst Phosphorus isn’t
    -There’s repulsion between the negatively charged electrons
    -So electrons are easier to remove

    What is the method of making a standardised solution of 250cm^3? (6 marks)
    -Weigh out known mass on weighing boat using a mass scale
    -Remember to deduct the mass of the weighing boat to find the exact mass of the solid. (or zero the scale mass)
    EDIT: You may not need this part as you've been told the known mass
    -Then transfer the contents into a beaker. Use distilled water to make sure all solids are in the beaker.
    -Then add bit more distilled water
    -Stir with a glass rod to make sure it's all mixed
    -Then pour solution into a Volumetric flask using a funnel
    -Clean the funnel with distilled water
    -Then fill the volumetric flask to the 250cm^3 mark. At near the mark use a pipette to add water dropwise and until meniscus is on the mark line.
    Then place stopper on it. Twist the volumetric flask a few times to ensure it's all mixed.

    Find mean titre value.
    Ignore the first number as it was the rough one when calculating mean.
    EDIT: You were only supposed to use 2 values that are 0.1 part when calculating mean.

    What was the concentration of the solution.

    Student titrated, what should she to improve her methods so there's a smaller percentage uncertainty?
    -Titrate a greater volume of solution
    -Why? So there's a greater value as percentage uncertainty= uncertainty/value *100. Bigger volume means there's a greater titre value.

    Why does Bromine have lower boiling point than Magnesium?
    -Bromine has a simple molecular structure.
    -There’s weak Van der Waals forces between molecules.
    -So smaller amount of energy needed to break these forces.
    -Magnesium has a metallic lattice.
    -It has many strong metallic bonds.
    -Bonds formed from the strong attraction between positiveions and delocalised electrons.
    -The metallic bonds are stronger than the Van der Waals forces

    How do the ions get accelerated, detected by ToF and how abundanceis measured?
    - Accelerated by negative electric field
    -The ions reach the detector and generate a small current, which is fed to a computer for analysis. The current is produced by electrons transferring from the detector to the positive ions. The size of the current is proportional to the abundance of the species.

    Calculation to find mass of one ion.
    1/Avogadro constant * mass. Then divide by 1000 to put it in Kg.
    Using kinetic energy, find velocity.
    Starts with 1........ Quite a large number.

    Draw the spectrum of Br2 with two isotopes of equal abundance.
    Attachment 539511

    Suggest why Magnesium has a longer melting point than Bromine. (Something like that?)
    -It has much more bonds than Bromine. So more bonds are needed to be broken when melting.
    a) Calculate the mass of Ammonia in Q?
    Basically use the ideal gas equation and usethe temp given, multiply the pressure by 1000 to convert it to SI Units, divide the volume by a million to convert to m^3 . Then use everything given to find the number of moles in Ammonia. Then find the mass of Ammonia using the mr.
    b) Calculate the volume in P given that the temperature decreased by 5 degrees and the total pressure is 75kPa?
    -Find volume of the whole system with the new values and use moles from previous question
    -Then subtract from the volume of Q given.

    Draw NH3 and AlCl3 and write the bonding angle.
    NH3- 1 Lone pair and 3 bonding pair. Should have drawn a trigonal pyrimidal.
    Bond angle- 107

    AlCl3- 3 bonding pair so Trigonal Planar
    Bond angle- 120

    What type of bond between NH3 and AlCl3 to make 3HNAlCl3?
    Dative covalent
    Electron pair donated from NH2 to AlCl3.

    What is the half equation of Chlorate(I) into Chlorine?
    2ClO- + 4H+ +2e- ---> Cl2 + 2H20

    What is the redox equation of Sodium Chlorate(I) and HCl?
    I have no idea.

    What's the observation when colourless Potassium iodide and Sodium Chloride are mixed and what reaction occurred for this to be seen?
    There was a brown solution seen, as Iodine ion was reduced to Iodine.

    Question on Anhydrous Magnesium Chloride and Anhydrous Barium Chloride mixture. Water was added and Sulphuric acid too. White precipitate was formed. What was this an find percentage of Magnesium in mixture?
    Barium Sulphate.
    Calculation:

    Multiple Choices:
    -Brown Colour is from the Reactant and forward is exothermic.
    -Empirical of hydrocarbon with 9/11th Carbon- C3H8
    -Doubts about biggest dipole. I put down BF3 and checked in my CGP book and states that bonds with electronegativity differences would make a dipole. Others argue that its Carbon one because BF3 is not polar.
    -Group 2's ionisation energy decreases downwards
    -There's 50cm^3 of gas in the end.
    -Gold is 19.3
    -SiO2 was Macromolecular
    -Balance was 4:7
    -The reducing agent was C204
    -How much sulphuric acid needed? D
    -Heavier isotope took longer in ToF
    -H2 Molecules was 1.81* 10^24
    The gas left over was 30 , you didnt take into account what was in excess and in limited. Dont post answers if they're wrong.
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    For the percentage of salt one, did you have to find the mass of the salt you wanted and divide by the original whole mass as times by 100?
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    (Original post by SM-)
    For the percentage of salt one, did you have to find the mass of the salt you wanted and divide by the original whole mass as times by 100?
    Two solutions used to get 35.5% - don't know if correct, but this it's what I got.

    "1.052g total in the solid, from memory. BaSO4 is the ppt as it is insoluble in water. Mass of ppt was something around 0.78, I think. (137.3/233.4) is proportion of Ba in BaSO4. So, (137.3/233.4)*0.78 (or whatever it was) is mass of barium in ppt. This is therefore the mass of the barium in the BaCl2.

    I used that to find the mass of the Cl in the BaCl2 using the fact that Cl ion is 1- and Ba ion is 2+. Therefore, you can find that the mass of the BaCl2 is 0.681 (from memory) and from that you can find the proportion of the MgCl2 in the solid at the start.

    With this you get 35.5%"

    "I can understand how you worked it out. I used another method by working out the number of moles using moles=mass/mr of baso4 then i wrote the equation bacl2+h2so4=baso4+2hcl and everything is a 1:1 ratio so the same moles of bacl2 were used. I worked out the mass of bacl2 from this using the mass=mr x moles. Then i took this away from the mass of both bacl2 and mgcl2 to work out how much mgcl2 there was. My answer was also 35.5%"
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    (Original post by britishtf2)
    Two solutions used to get 35.5% - don't know if correct, but this it's what I got.

    "1.052g total in the solid, from memory. BaSO4 is the ppt as it is insoluble in water. Mass of ppt was something around 0.78, I think. (137.3/233.4) is proportion of Ba in BaSO4. So, (137.3/233.4)*0.78 (or whatever it was) is mass of barium in ppt. This is therefore the mass of the barium in the BaCl2.

    I used that to find the mass of the Cl in the BaCl2 using the fact that Cl ion is 1- and Ba ion is 2+. Therefore, you can find that the mass of the BaCl2 is 0.681 (from memory) and from that you can find the proportion of the MgCl2 in the solid at the start.

    With this you get 35.5%"

    "I can understand how you worked it out. I used another method by working out the number of moles using moles=mass/mr of baso4 then i wrote the equation bacl2+h2so4=baso4+2hcl and everything is a 1:1 ratio so the same moles of bacl2 were used. I worked out the mass of bacl2 from this using the mass=mr x moles. Then i took this away from the mass of both bacl2 and mgcl2 to work out how much mgcl2 there was. My answer was also 35.5%"
    So in the last step once you worked out the mass of MgCl2 did you have to divide that mass y the mass of the whole mixture of MgCl2 and BaCl2 then times by 100?
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    (Original post by SM-)
    So in the last step once you worked out the mass of MgCl2 did you have to divide that mass y the mass of the whole mixture of MgCl2 and BaCl2 then times by 100?
    Yes. Once you get the mass of BaCl2, you do:
    {[1-(mass of BaCl2)]/(Total mass of solid)}*100
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    (Original post by britishtf2)
    Yes. Once you get the mass of BaCl2, you do:
    {[1-(mass of BaCl2)]/(Total mass of solid)}*100
    Ok, thanks! I was wondering whether I got the right answer because I can't remember it but I'm sure I did all those steps so fingers crossed I got it right!
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    (Original post by SM-)
    Ok, thanks! I was wondering whether I got the right answer because I can't remember it but I'm sure I did all those steps so fingers crossed I got it right!
    Hopefully you did. Good luck in paper 2
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    Hardest exam Ive ever sat
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    (Original post by Cinna21)
    Are you sure its Mg2+ I'm sure It's Na+ which has the smaller ion
    Ionic radius decreases across periods, doesn’t it?
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    (Original post by framgbed99)
    Ionic radius decreases across periods, doesn’t it?
    Yes. More protons, so stronger attraction, so electrons are pulled closer to the nucleus.
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    Has anyone made a poll on this paper on how hard people found it, so we can maybe get an idea of possible grade boundaries?
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    (Original post by voltz)
    Has anyone made a poll on this paper on how hard people found it, so we can maybe get an idea of possible grade boundaries?
    My prediction is that it is going to be standard boundaries or less. Maybe down to 70-75%. Not sure, though.
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    Was there any question on this paper with an answer of 138?
    • Thread Starter
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    Just added some other answers about the Mr of that isotope, the chloride ion half equation and the last part of the bond angle question to my first post. Check if it's right.

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    (Original post by voltz)
    Has anyone made a poll on this paper on how hard people found it, so we can maybe get an idea of possible grade boundaries?
    No, I haven't seen one yet.

    Posted from TSR Mobile
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    (Original post by britishtf2)
    Yes. More protons, so stronger attraction, so electrons are pulled closer to the nucleus.
    Hey, I was wondering if you remember how many marks was that Barium sulphate question was? Thanks!

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    (Original post by DaVinciGirl)
    Hey, I was wondering if you remember how many marks was that Barium sulphate question was? Thanks!

    Posted from TSR Mobile
    it was 4 marks
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    does anyone have any good notes, links or know any videos to help me learn the practicals for paper 2?
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    (Original post by DaVinciGirl)
    If you know anymore questions or answers please reply and the number of marks.
    What is the full electronic configuration of Al? 1s2,2s2,2p6,3s2,3p1

    What is the full electronic configuration for Cr+3? 1s2,2s2,2p6,3s2,3p6,3d3

    What is the formula of the ion with same electronic configuration of Krypton?
    Sr2+ (strontium)

    What compound has a +2 and -3 ions and has the same number electrons as Argon?
    Ca3P2

    Which ion has a smaller atomic radius Mg2+ or Na+?
    Mg 2+
    because has the same number of electrons, same shielding but more protons. So greater nuclear charge and attraction for outer electrons.

    What is the first ionisation energy of Na?
    Na (g) --> Na+ (g) + e-
    Diagram-Mark where the Mg or was it Si?
    Was and then mark the point where Sulphur was on the First ionisation graph.
    Mg/Si should have been above so the line was increasing.
    Sulphur should have been below Phosphorus but above Silicon.

    Why does Sulphur have a different first ionisation energy compared to Phosphorus?
    -Both have same shielding and in the same orbital the 3p orbital
    -Sulphur is paired with an electron in the 3p orbital whilst Phosphorus isn’t
    -There’s repulsion between the negatively charged electrons
    -So electrons are easier to remove

    What is the method of making a standardised solution of 250cm^3? (6 marks)
    -Weigh out known mass on weighing boat using a mass scale
    -Remember to deduct the mass of the weighing boat to find the exact mass of the solid. (or zero the scale mass)
    EDIT: You may not need this part as you've been told the known mass
    -Then transfer the contents into a beaker. Use distilled water to make sure all solids are in the beaker.
    -Then add bit more distilled water
    -Stir with a glass rod to make sure it's all mixed
    -Then pour solution into a Volumetric flask using a funnel
    -Clean the funnel with distilled water
    -Then fill the volumetric flask to the 250cm^3 mark. At near the mark use a pipette to add water dropwise and until meniscus is on the mark line.
    Then place stopper on it. Twist the volumetric flask a few times to ensure it's all mixed.

    Find mean titre value.
    Ignore the first number as it was the rough one when calculating mean.
    EDIT: You were only supposed to use 2 values that are 0.1 part when calculating mean.

    What was the concentration of the solution.

    Student titrated, what should she to improve her methods so there's a smaller percentage uncertainty?
    -Titrate a greater volume of solution
    -Why? So there's a greater value as percentage uncertainty= uncertainty/value *100. Bigger volume means there's a greater titre value.

    Why does Bromine have lower boiling point than Magnesium?
    -Bromine has a simple molecular structure.
    -There’s weak Van der Waals forces between molecules.
    -So smaller amount of energy needed to break these forces.
    -Magnesium has a metallic lattice.
    -It has many strong metallic bonds.
    -Bonds formed from the strong attraction between positiveions and delocalised electrons.
    -The metallic bonds are stronger than the Van der Waals forces

    How do the ions get accelerated, detected by ToF and how abundanceis measured?
    - Accelerated by negative electric field
    -The ions reach the detector and generate a small current, which is fed to a computer for analysis. The current is produced by electrons transferring from the detector to the positive ions. The size of the current is proportional to the abundance of the species.

    Calculation to find mass of one ion.
    1/Avogadro constant * mass. Then divide by 1000 to put it in Kg.
    Using kinetic energy, find velocity.
    Starts with 1........ Quite a large number.

    Draw the spectrum of Br2 with two isotopes of equal abundance.
    Attachment 539511

    What's the Mr of the isotope?
    Maybe 138, need to clarify that one.

    Suggest why Magnesium has a longer melting point than Bromine. (Something like that?)
    -It has much more bonds than Bromine. So more bonds are needed to be broken when melting.
    a) Calculate the mass of Ammonia in Q?
    Basically use the ideal gas equation and usethe temp given, multiply the pressure by 1000 to convert it to SI Units, divide the volume by a million to convert to m^3 . Then use everything given to find the number of moles in Ammonia. Then find the mass of Ammonia using the mr.
    b) Calculate the volume in P given that the temperature decreased by 5 degrees and the total pressure is 75kPa?
    -Find volume of the whole system with the new values and use moles from previous question
    -Then subtract from the volume of Q given.

    Draw NH3 and AlCl3 and write the bonding angle.
    NH3- 1 Lone pair and 3 bonding pair. Should have drawn a trigonal pyrimidal.
    Bond angle- 107

    AlCl3- 3 bonding pair so Trigonal Planar
    Bond angle- 120

    What type of bond between NH3 and AlCl3 to make 3HNAlCl3?
    Dative covalent
    Electron pair donated from NH2 to AlCl3.

    Is there a new change in the bond angle around All in the 3HNAlCl3 and why?
    Yes, bond angles decrease. As there is an extra bonding pair and they repel equally and as far apart as possible.

    Half equation for chloride ion to chlorine?
    2Cl- ---> Cl2 + 2e-
    What is the half equation of Chlorate(I) into Chlorine?
    2ClO- + 4H+ +2e- ---> Cl2 + 2H20

    What is the redox equation of Sodium Chlorate(I) and HCl?
    I have no idea.

    What's the observation when colourless Potassium iodide and Sodium Chloride are mixed and what reaction occurred for this to be seen?
    There was a brown solution seen, as Iodine ion was reduced to Iodine.

    Question on Anhydrous Magnesium Chloride and Anhydrous Barium Chloride mixture. Water was added and Sulphuric acid too. White precipitate was formed. What was this an find percentage of Magnesium in mixture?
    Barium Sulphate.
    Calculation:

    Multiple Choices:
    -Brown Colour is from the Reactant and forward is exothermic.
    -Empirical of hydrocarbon with 9/11th Carbon- C3H8
    -Doubts about biggest dipole. I put down BF3 and checked in my CGP book and states that bonds with electronegativity differences would make a dipole. Others argue that its Carbon one because BF3 is not polar.
    -Group 2's ionisation energy decreases downwards
    -There's 50cm^3 of gas in the end.
    -Gold is 19.3
    -SiO2 was Macromolecular
    -Balance was 4:7
    -The reducing agent was C204
    -How much sulphuric acid needed? D
    -Heavier isotope took longer in ToF
    -H2 Molecules was 1.81* 10^24

    for ful redox equation you just combine the two half equations and eliminate the electrons so
    2Cl+2CLO-+4H ---> 2CL2 + 2H2O
 
 
 
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