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Edexcel Official Chemistry Paper1:Core Inorganic and Physical Chemistry - 27th of May

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Original post by clairebear101
yep i did it this way so did everyone else i know


oh well wasnt that many marks, probably get working marks or something
Original post by clairebear101
oh well wasnt that many marks, probably get working marks or something

Lets take chlorine for example. If there is 35.5g of chlorine with 26.25g of Cl-35 and 9.25g of Cl-37 the answer should be that the molar mass is 35.5gmol-1. However using the method you did you obtain 35.52. Although the method is a good approximation it does take into account the moles of each isotope. So only works for isotopes with very high masses of very similar masses as this reduces the error.
Original post by Cryptokyo
Lets take chlorine for example. If there is 35.5g of chlorine with 26.25g of Cl-35 and 9.25g of Cl-37 the answer should be that the molar mass is 35.5gmol-1. However using the method you did you obtain 35.52. Although the method is a good approximation it does take into account the moles of each isotope. So only works for isotopes with very high masses of very similar masses as this reduces the error.


i just did it how we normally do it from isotopic abundances, so okay i have done it wrong, i didnt get it at the time and wouldnt have realised thats the maths to do... im dropping maths, hopefully i'll still get a mark
Original post by Cryptokyo
Lets take chlorine for example. If there is 35.5g of chlorine with 26.25g of Cl-35 and 9.25g of Cl-37 the answer should be that the molar mass is 35.5gmol-1. However using the method you did you obtain 35.52. Although the method is a good approximation it does take into account the moles of each isotope. So only works for isotopes with very high masses of very similar masses as this reduces the error.


yes but considering that the method that is taught, and that is one the specification, is the one that she has used there will be no problem. The markscheme will likely have a correct answer, then in the guidance column an 'expect' part with the other value depending on the method, meaning people will get the marks either way.

Personally I just found the percentage abundancies by doing 0.460/5.00 x 100, and then did it the usual way.

Original post by clairebear101
i just did it how we normally do it from isotopic abundances, so okay i have done it wrong, i didnt get it at the time and wouldnt have realised thats the maths to do... im dropping maths, hopefully i'll still get a mark
Original post by richpanda
yes but considering that the method that is taught, and that is one the specification, is the one that she has used there will be no problem. The markscheme will likely have a correct answer, then in the guidance column an 'expect' part with the other value depending on the method, meaning people will get the marks either way.

Personally I just found the percentage abundancies by doing 0.460/5.00 x 100, and then did it the usual way.


okay thank you, i hope so :smile: yeah thats what the spec says to do and yes that means you got the same answer as me :smile: as i checked my answer doing it your way :smile:
Original post by richpanda
yes but considering that the method that is taught, and that is one the specification, is the one that she has used there will be no problem. The markscheme will likely have a correct answer, then in the guidance column an 'expect' part with the other value depending on the method, meaning people will get the marks either way.

Personally I just found the percentage abundancies by doing 0.460/5.00 x 100, and then did it the usual way.


The percentage abundancy by mass does not tell you the abundancy in terms of the ratio of the isotopes. The method you are using is for when the abundancies are given from a mass spectrum and not when individual masses are different.
(edited 7 years ago)
Anyway, lets stop fussing over that question now. Are there any other questions anyone has or is this the natural end of the thread?
What three points did you put for improving the molar volume of a gas experiment?
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sc67
Original post by SolomonP
What three points did you put for improving the molar volume of a gas experiment?


I wrote about how you could use a gas syringe, this would make it easier to read the values and how you could increase the temperature so more gas could be released. I can't remember my third point sorry . Idk if this is right , but it's what I put down.
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sc67
For the six marker at the end , the question was something along the lines of : X exhibits some characteristics of a metal, X could be a metal , state and explain 2 physical properties X would have if it a metal?

I talked about how it would have free delocalised electrons within the giant metallic lattice , these electrons would allow for current to flow , therefore the metal can conduct electricity as a solid. I also wrote about how within the metal lattice there are strong electrostatic forces of attraction between the positive metal ion and the sea of delocalised electrons. This enables the metal to have an orderly arrangement of the metallic ions being surrounded by the free electrons . You could have also mentioned that metals are ductile and could be stretched into wires and that they are malleable and can be bent into shapes provided a force is applied onto them .
Original post by sc67
I wrote about how you could use a gas syringe, this would make it easier to read the values and how you could increase the temperature so more gas could be released. I can't remember my third point sorry . Idk if this is right , but it's what I put down.


I mentioned the gas syringe too, and said how the cylinder has a lower resolution than a gas syringe. I then had no idea what to write, so I just made stuff up, like the Magnesium ribbon is too big so a lot of gas would be made as there's a lot of acid. So I think I gained about 2 marks :/


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sc67
What did anyone draw for the equipment set up for measuring the thermal decomposition rate of the carbonate and nitrate?
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sc67
Original post by Florent venhari
I mentioned the gas syringe too, and said how the cylinder has a lower resolution than a gas syringe. I then had no idea what to write, so I just made stuff up, like the Magnesium ribbon is too big so a lot of gas would be made as there's a lot of acid. So I think I gained about 2 marks :/


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I think it was worth around 5 marks & you probably have , one mark for stating one marks for explain the reasoning behind it . Now that I think about it , another point could have been to scrub the metal surface of the magnesium ribbon as a layer of oxide forms which could give a false positive.
Original post by sc67
What did anyone draw for the equipment set up for measuring the thermal decomposition rate of the carbonate and nitrate?


A test tube fitted with a bung which has a delivery tube fitted to another test tube with limewater in it. Measure the rate of CO2 made


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Original post by richpanda
For titration:

Average titre of 19.95cm^3 of 0.08 moldm^3 NaOH, so 0.08 x 0.01995 = 0.001596mol of acid in 25cm^3.

Therefore 0.01956 mol of acid in 250cm^3. This is the diluted bit of acid. They added 10cm^3 of pure acid, so concentration is 0.01956/0.01 = 1.596 moldm^3.

Multiply this by the molar mass of nitric acid (63) to get 100.548 gdm^3.

Therefore the acid is suitable.

I got this answer and then showed it could be rounded to 101 if u used 3sf and said it was suitable, is this okay?
Original post by clairebear101
I got this answer and then showed it could be rounded to 101 if u used 3sf and said it was suitable, is this okay?


yes
Original post by sc67
I think it was worth around 5 marks & you probably have , one mark for stating one marks for explain the reasoning behind it . Now that I think about it , another point could have been to scrub the metal surface of the magnesium ribbon as a layer of oxide forms which could give a false positive.

This question sucked, haha. anyway i said that some of the H2 gas could dissolve in the water. To reduce this use a gas syrine. I said use more concentrated acid as this would prduce a larger volume of gas that would reduce percentage uncertainty. I said some of the gas may have escaped when the magnesium was inserted. Use a delivery tube to a conical flask where the two reactants are mixed in the conical flask without bung removal. Think i then said something aobut insuring all the magnesium strips were the same width and aswell as lenght, i dunno if any of that will get me marks, might get 2/6
Original post by clairebear101
I said use more concentrated acid as this would prduce a larger volume of gas that would reduce percentage uncertainty.


A more concentrated acid does not affect the volume of H2 produced as the magnesium strip is still the limiting factor; it would only affect the rate of production of hydrogen gas.
I know but didn't have anything else to say at all haha
Good luck for paper 2 everyone

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