Right, last question on the chemistry practical, i promise.
On the June 2004 paper i'm really stuck on part 2 of the planning exercise.
You're given the equation: Sr(s) + 2HCl(aq) gives SrCl2(aq) + H2 (g) The question is; find a suitable mass of strontium to be used. Assume that the volume of one mole of hydrogen is 24dm^3.
Please could someone talk me through this and explain why the mark scheme says that 0.37g of Sr produces 100 cm^3 of hydrogen - how did they work this out and where did 0.37 come from?
I'm probably being stupid, so any help would be really really appreciated.
You need to have an amount that would give off a reasonable amount of gas, not too much, not too little.
You just need to calculate the number of moles of Sr being used and divide by 24000, this then gives you the volume in cm^3. This is because one mole of Sr leads to one mole of Hydrgen gas being given off
Right, last question on the chemistry practical, i promise.
On the June 2004 paper i'm really stuck on part 2 of the planning exercise.
You're given the equation: Sr(s) + 2HCl(aq) gives SrCl2(aq) + H2 (g) The question is; find a suitable mass of strontium to be used. Assume that the volume of one mole of hydrogen is 24dm^3.
Please could someone talk me through this and explain why the mark scheme says that 0.37g of Sr produces 100 cm^3 of hydrogen - how did they work this out and where did 0.37 come from?
I'm probably being stupid, so any help would be really really appreciated.
Thanks
do you have any ideas what will come up in the plan tomorrow??
Right, last question on the chemistry practical, i promise.
On the June 2004 paper i'm really stuck on part 2 of the planning exercise.
You're given the equation: Sr(s) + 2HCl(aq) gives SrCl2(aq) + H2 (g) The question is; find a suitable mass of strontium to be used. Assume that the volume of one mole of hydrogen is 24dm^3.
Please could someone talk me through this and explain why the mark scheme says that 0.37g of Sr produces 100 cm^3 of hydrogen - how did they work this out and where did 0.37 come from?
I'm probably being stupid, so any help would be really really appreciated.
Thanks
do you have any past papers for 3A i would be so grateful if you can send it to me...do you have the recent ones lyk from 2004-2008 with markschemes please *shee begs on her knees"
I'm still not quite sure where the markscheme's answer came from though?
theunknown, nope i've got no idea what's gonna come up so i'm covering all possibilities - better safe than sorry Have you looked on the aqa website for some past exam questions, they're always good?
I think its just a note to the examiner as such saying that 0.37g gives 100ml. Its been a long time since i did a-levels but do you get a list of equipment? If you (say) had a 100ml measuring cylinder then it would be unsuitable to use more than 0.37g. If this were me i would have probably calculated what 1g of Sr would have given, thought it were too much and tried 0.5g and so on until i got a reasonable figure for the equipment i would use.